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Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: grondilu on 08/22/2013 05:10 pm

Title: ESA - Gaia updates
Post by: grondilu on 08/22/2013 05:10 pm
I could not find a thread about this one, so I create one.  Sorry if there was actually one.

So it seems that friday the Gaia telescope is going to fly to Guyana in preparation for its launch in a few months.

http://www.bbc.co.uk/news/science-environment-23779294


I got to say that to me Gaia is one of the most exciting upcoming mission for the next few years, along with Dawn and New Horizons.

Title: Re: ESA - Gaia updates
Post by: bolun on 02/06/2014 01:02 pm
Gaia's launch thread:

Soyuz Flight VS06 Soyuz-STB/Fregat-MT - Gaia December 19, 2013

http://forum.nasaspaceflight.com/index.php?topic=19838.0
Title: Re: ESA - Gaia updates
Post by: bolun on 02/06/2014 01:05 pm
Gaia comes into focus

6 February 2014

ESA’s billion-star surveyor Gaia is slowly being brought into focus. This test image shows a dense cluster of stars in the Large Magellanic Cloud, a satellite galaxy of our Milky Way.

Once Gaia starts making routine measurements, it will generate truly enormous amounts of data. To maximise the key science of the mission, only small ‘cut-outs’ centred on each of the stars it detects will be sent back to Earth for analysis.

This test picture, taken as part of commissioning the mission to ‘fine tune’ the behaviour of the instruments, is one of the first proper ‘images’ to be seen from Gaia, but ironically, it will also be one of the last, as Gaia's main scientific operational mode does not involve sending full images back to Earth.

Gaia was launched on 19 December 2013, and is orbiting around a virtual point in space called L2, 1.5 million kilometres from Earth.

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_comes_into_focus

Image credit: ESA/DPAC/Airbus DS
Title: Re: ESA - Gaia updates
Post by: bolun on 02/13/2014 09:07 am
One month at L2 (interim status report)

http://blogs.esa.int/gaia/2014/02/12/one-month-at-l2/
Title: ESA - Gaia updates
Post by: Star One on 02/13/2014 03:58 pm
One month at L2 (interim status report)

http://blogs.esa.int/gaia/2014/02/12/one-month-at-l2/

Thanks. Interesting that they are going to have to change its angle to attempt to eliminate the stray sunlight issue. Shows you still that there is a limit to how much you can model things such as this on the ground to try and avoid them.
Title: Re: ESA - Gaia updates
Post by: jebbo on 02/17/2014 08:24 am
Images of Gaia at L2 from the VST at Paranal

http://www.eso.org/public/images/potw1407a/

Title: Re: ESA - Gaia updates
Post by: bolun on 03/05/2014 11:11 am
Gaia: on the right track

http://www.astrium.eads.net/en/news2/gaia-on-the-right-track.html
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/15/2014 10:04 am
@ESAGaia: Weekend full of measurements for the best focus search. Maybe not the last round yet, but #Gaia is pretty close to the final settings.
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2014 07:32 am
Commissioning Update

24 April 2014

The Gaia project team provides an update on the ongoing commissioning activities of ESA’s billion star surveyor…

The work done to bring online all components of the Gaia service module, which houses equipment needed for the basic control and operation of the satellite, has gone very smoothly. The chemical and micro propulsion systems function well, with the latter providing tiny (micro-Newton) thrusts to maintain Gaia’s spin rate, compensating for torques due to solar radiation pressure. The phased array antenna is operating very well, ensuring that we can maintain the high data rates that are needed to downlink all the science data. And the essential rubidium atomic clock is also working to specification.

The Gaia scientific payload is also functioning very well. This includes all 106 CCD detectors and the associated electronics units, as well as the seven on-board computers that manage the CCD’s. Alignment and co-focusing of the two telescopes through their movable secondary mirrors is working as expected. Following the last displacement of one of the secondary mirrors by just 3 micrometres, we are currently at the optimal image quality that Gaia can deliver, well balanced across the large focal plane and the three instruments. This is no small achievement considering the complexity of the optics!

However, a few other aspects of the commissioning have been progressing somewhat less smoothly.

In order to deliver exquisitely precise measurements of the positions of stars on the sky, we need in turn to know where Gaia itself is in space very accurately at any given moment. The distance part of Gaia’s orbit is readily determined from radio signals sent back and forth, but the position on the plane of the sky needs ground-based telescope observations of the satellite.

It turns out that Gaia is much fainter in the sky than hoped for, at magnitude 21 rather than 18, and thus the smaller 1 metre diameter class telescopes planned to be used by Gaia’s GBOT network  are not big enough to detect Gaia in a reasonable amount of time. But by shifting the bulk of the observations to the 2.0-m Liverpool Telescope on La Palma and ESO’s 2.6-m VST on Paranal, as well as introducing Very Long Baseline Interferometry radio measurements, the problem is now under control.

Near the beginning of commissioning, a steady drop in the transmission of Gaia’s telescopes was seen, due to water-ice deposits building up on the mirrors as trapped water vapour was liberated from the satellite after launch. The transmission was fully recovered following a decontamination campaign, during which the payload was heated to remove the ice from the optics.

Ice deposits are thought to play a part in another concern, in which unanticipated ‘stray light’ is seen hitting parts of the Gaia focal plane. Some of the stray light is thought to come from sunlight diffracted around the edges of the sunshield and entering the telescope apertures. There also seems to be a smaller contribution from night sky sources reaching the focal plane via unexpected paths.

Although the diffracted sunlight component was foreseen, we think that it is enhanced by reflections off ice deposits on the ceiling of the ‘thermal tent’ structure surrounding the payload, allowing it to reach the focal plane. It was hoped that the decontamination campaign would also remove this ice layer, but unfortunately the stray light is still there at the moment.

Careful preparations are being made for one more attempt to remove the water ice and, hopefully, the stray light. But in parallel, we are now continuing with the nominal commissioning and a detailed performance verification phase. Even if the stray light remains, the current best assessment is that degradation in science performance will be relatively modest and mostly restricted to the faintest of Gaia’s one billion stars.

We will, of course, provide an update on the blog when we have new information to share.

See http://blogs.esa.int/gaia/2014/04/24/commissioning-update/

--- Tony
Title: Re: ESA - Gaia updates
Post by: baldusi on 04/25/2014 02:21 pm
Funny how difficult is this science. I still don't quite understand how did they miscalculated the apparent magnitude by three orders of magnitude. Is that normal?
Title: Re: ESA - Gaia updates
Post by: as58 on 04/25/2014 04:07 pm
Funny how difficult is this science. I still don't quite understand how did they miscalculated the apparent magnitude by three orders of magnitude. Is that normal?

Not quite by three orders of magnitude, although even three magnitudes is a lot...
Title: Re: ESA - Gaia updates
Post by: baldusi on 04/25/2014 06:22 pm
Funny how difficult is this science. I still don't quite understand how did they miscalculated the apparent magnitude by three orders of magnitude. Is that normal?

Not quite by three orders of magnitude, although even three magnitudes is a lot...
I've just seen the 2.5 multiplier in front of the Log10. I'm used to Ln or Log10, but 2.5 x Log10 seems... counter intuitive. So it's not that bad, 15X less luminosity. Still more than an order of magnitude. It would be interesting to understand why they miscalculated. This isn't the first L2 mission they have. May be they never had to track optically? Change in MLI?
Title: Re: ESA - Gaia updates
Post by: ngc3314 on 05/04/2014 08:28 pm
Funny how difficult is this science. I still don't quite understand how did they miscalculated the apparent magnitude by three orders of magnitude. Is that normal?

Not quite by three orders of magnitude, although even three magnitudes is a lot...
I've just seen the 2.5 multiplier in front of the Log10. I'm used to Ln or Log10, but 2.5 x Log10 seems... counter intuitive.
Blame Hipparchus and astronomers' great respect for historical continuity...

Quote
This isn't the first L2 mission they have. May be they never had to track optically? Change in MLI?

AFAIK this is the first deep-space mission with an actual optical tracking requirement. 1m telescopes have certainly been able to detect things near L2 (I did Herschel with a 0.6m, and apparently provided one of the first reports that Gaia had gotten much fainter when oriented in its operational mode). LCROSS was not hard with a 0.4m in light-polluted skies, but that ws still pretty big and a good bit closer. I suspect it was lack of that much of an observational database to show just what a big difference the smoothness of the surface made. (The hindsight part of my brain is yelling "Hello? Iridium flares, anybody?")

The tracking requirement to meet the mission error budget is pretty impressive - 150 meters, IIRC, and the "cross-track" part of that is supposed to include optical tracking and maybe radio interferometry. I don't know how often they need to get optical astrometry to do that - there are 2m telescopes being decommissioned in the US and Europe anyway, and L2 is visible from both hemispheres. There's certainly the lunar month to deal with - not only is the full Moon disruptively bright but it's pretty much in front of the L2 orbits. (Neither of which matters if you go into the near-IR, certainly by 2.2 microns moonlight barely matters).
Title: Re: ESA - Gaia updates
Post by: baldusi on 05/04/2014 10:41 pm
150m at SEL2 is 10e-7 of error? That's very strong requirement. So much that not any telescope can have the necessary alignment requirements.
Title: Re: ESA - Gaia updates
Post by: ngc3314 on 05/05/2014 01:05 am
That precision doesn't have to be absolute in the telescope's mechanical reference frame; it is with respect to a network of background stars whose coordinates are known at a level as good as milliarcseconds in, for example, the HIPPARCOS approximation of an inertial frame. This relative accuracy, in astronomically familiar units, will be about 1.5e-7*206265=0.03 arcseconds, which is well within routine astrometric accuracy if there are enough photon counts for that not to be a major contributor. Typically one would take a sequence of exposures (below a minute or so there are residual atmospheric effects you'd want to average anyway), so the accuracy of a whole track could be improved further.
Title: Re: ESA - Gaia updates
Post by: bolun on 06/10/2014 08:46 pm
Gaia takes science measurements

http://blogs.esa.int/gaia/2014/06/05/gaia-takes-science-measurements/
Title: Re: ESA - Gaia updates
Post by: bolun on 06/16/2014 04:24 pm
http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/

Preliminary analysis of stray light impact and strategies

Quote
A series of exhaustive tests have been conducted over the past few months to characterise some anomalies that have been revealed during the commissioning of Gaia following its successful launch in December 2013

Quote
A comprehensive understanding of these issues will be given when a thorough analysis of all engineering tests is complete. Gaia has nearly completed its performance verification data taking, and is about to start a month-long dedicated science observation run. Once the data have been fully analysed, we will be able to provide a detailed quantitative assessment of the scientific performance of Gaia.

While there will likely be some loss relative to Gaia’s pre-launch performance predictions, we already know that the scientific return from the mission will still be immense, revolutionising our understanding of the formation and evolution of our Milky Way galaxy and much else.
Title: Re: ESA - Gaia updates
Post by: gosnold on 06/16/2014 06:47 pm
That's a lot of unexpected problems, though the science impact seems limited.
Title: Re: ESA - Gaia updates
Post by: gosnold on 06/25/2014 06:50 pm
I attended a presentation on the gaia mission and its issues.

Their problem is that they have stray light (as mentioned in http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/ (http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/)), ie light striking the focal plane and not coming from the standard path through mirrors, which degrades instrument performance. Its seems to be caused by a combination of two things: the sunshade was designed with a diameter just large enough to hide the housing of the instrument from the sun, but the designers considered light travelling in a straight path and forgot the diffraction effects. The other cause is that they think they have ice inside the instrument housing, which reflects light in random directions (they don't know for sure because they have no camera inside or outside the spacecraft).

They have tried to change the attitude of the spacecraft to block more light with the sunshade, and it indeed reduces the amount of stray light. But the communication system cannot steer the downlink beam in the right direction with the new attitude, because the standard attitude is harcoded somewhere in the system. So they are back to square one.
They plan to change the attitude in the opposite direction to have sunlight heating the instrument housing and removing some ice, and then letting it cool off, and start the science campaign afterwards.

Apparently the relationship between the scientists and Airbus is a bit tense sometimes.
Title: Re: ESA - Gaia updates
Post by: Star One on 06/25/2014 10:52 pm

That's a lot of unexpected problems, though the science impact seems limited.

Does this remain the case even in light of your latest post?
Title: Re: ESA - Gaia updates
Post by: denis on 06/26/2014 07:52 pm
I attended a presentation on the gaia mission and its issues.

Their problem is that they have stray light (as mentioned in http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/ (http://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-of-stray-light-impact-and-strategies/)), ie light striking the focal plane and not coming from the standard path through mirrors, which degrades instrument performance. Its seems to be caused by a combination of two things: the sunshade was designed with a diameter just large enough to hide the housing of the instrument from the sun, but the designers considered light travelling in a straight path and forgot the diffraction effects. The other cause is that they think they have ice inside the instrument housing, which reflects light in random directions (they don't know for sure because they have no camera inside or outside the spacecraft).

They have tried to change the attitude of the spacecraft to block more light with the sunshade, and it indeed reduces the amount of stray light. But the communication system cannot steer the downlink beam in the right direction with the new attitude, because the standard attitude is harcoded somewhere in the system. So they are back to square one.
They plan to change the attitude in the opposite direction to have sunlight heating the instrument housing and removing some ice, and then letting it cool off, and start the science campaign afterwards.

Apparently the relationship between the scientists and Airbus is a bit tense sometimes.

Good to have some news, though from the article, it seems they don't really know what is the cause (they suspect ice deposit but testing in labs don't seem to confirm this possibility).

For the change of attitude (pointing the Sun perpendicular to the sun shield), it was done to see if the direction of the Sun has any impact on the stray light, not as a real alternative for the rest of the mission. I don't think they would get as much science return by doing that (they would not cover the sky as well as having an inclination to the Sun). In any case, it's true the phased-array antenna cannot (physically) steer the beam in that direction, so they would not be able to get the data back.

As for having a camera inside or outside, it would be no use as everything would be pitch black. Given it works at all, the level of stray light must be lower than a star of magnitude 20, which I assure you represent very little light ;)
Title: Re: ESA - Gaia updates
Post by: gosnold on 06/26/2014 07:53 pm
Quote

Quote from: gosnold on 06/16/2014 06:47 PM

    That's a lot of unexpected problems, though the science impact seems limited

Does this remain the case even in light of your latest post?
The Radial Velocity Spectrometer is unaffected, and I think the other spectrometer too. The astrometry sensor has a degraded performance for 20-21 mag stars, so they plan to focus on the stars with mag<20 and give them a higher share of the downloads bandwidth to get better data on those stars. Things will change depending on what happens when they warm the satellite. We will know for sure after the official commissioning.

Quote
As for having a camera inside or outside, it would be no use as everything would be pitch black. Given it works at all, the level of stray light must be lower than a star of magnitude 20, which I assure you represent very little light ;)
Yes but a camera outside would have been nice to visually check for correct sunshade deployment.

Title: Re: ESA - Gaia updates
Post by: denis on 06/26/2014 08:01 pm
Quote
As for having a camera inside or outside, it would be no use as everything would be pitch black. Given it works at all, the level of stray light must be lower than a star of magnitude 20, which I assure you represent very little light ;)
Yes but a camera outside would have been nice to visually check for correct sunshade deployment.

That's a good point actually!
Title: Re: ESA - Gaia updates
Post by: as58 on 06/27/2014 07:26 am
The Radial Velocity Spectrometer is unaffected, and I think the other spectrometer too.

The Gaia blog post says that the RVS is most affected by the stray light and loses about 1.5 mag of sensitivity. Do you have other information?
Title: Re: ESA - Gaia updates
Post by: bolun on 07/05/2014 04:20 pm
Commissioning the Radial Velocity Spectrometer

http://blogs.esa.int/gaia/2014/06/27/commissioning-the-radial-velocity-spectrometer/

Asteroids at the “photo finish”

http://blogs.esa.int/gaia/2014/07/03/asteroids-at-the-photo-finish/
Title: Re: ESA - Gaia updates
Post by: gosnold on 07/06/2014 09:04 am
The Radial Velocity Spectrometer is unaffected, and I think the other spectrometer too.

The Gaia blog post says that the RVS is most affected by the stray light and loses about 1.5 mag of sensitivity. Do you have other information?

That's curious, the information I was given is the opposite,  I will ask again if I can.
Title: Re: ESA - Gaia updates
Post by: Star One on 07/06/2014 06:45 pm
New article covering Gaia's trouble and detailing a delay in data collection.

http://www.newscientist.com/article/dn25847-first-data-from-space-megacamera-delayed-nine-months.html#.U7mYtWK9KSM
Title: Re: ESA - Gaia updates
Post by: bolun on 07/29/2014 01:11 pm
http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_Go_for_science

Gaia: ‘Go’ for science

Quote

Following extensive in-orbit commissioning and several unexpected challenges, ESA’s billion-star surveyor, Gaia, is now ready to begin its science mission.
Title: Re: ESA - Gaia updates
Post by: denis on 07/29/2014 09:50 pm

More detailed report on:

http://www.cosmos.esa.int/web/gaia/news_20140729 (http://www.cosmos.esa.int/web/gaia/news_20140729)

Some information not yet publicly released as far as I know, including:

Quote
- the cold-gas consumption of the micro-propulsion system is low enough to allow for a mission extension exceeding the nominal 1-year extension after the 5-year routine phase;

If all goes well, this means there could me mission extensions which could counterbalance to some level the slight degradation in predicted performances due to stray light.
Title: Re: ESA - Gaia updates
Post by: Lewis007 on 07/31/2014 08:28 am
Another article describing the problems encountered during the commissioning phase of Gaia:
http://www.spaceflight101.com/gaia-mission-updates.html
Title: Re: ESA - Gaia updates
Post by: bolun on 09/12/2014 09:22 am
Gaia discovers its first supernova

12 September 2014

While scanning the sky to measure the positions and movements of stars in our Galaxy, Gaia has discovered its first stellar explosion in another galaxy far, far away.

This powerful event, now named Gaia14aaa, took place in a distant galaxy some 500 million light-years away, and was revealed via a sudden rise in the galaxy’s brightness between two Gaia observations separated by one month.

Gaia, which began its scientific work on 25 July, repeatedly scans the entire sky, so that each of the roughly one billion stars in the final catalogue will be examined an average of 70 times over the next five years.

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_discovers_its_first_supernova

Image credit: M. Fraser/S. Hodgkin/L. Wyrzykowski/H. Campbell/N. Blagorodnova/Z. Kostrzewa-Rutkowska/Liverpool Telescope/SDSS
Title: Re: ESA - Gaia updates
Post by: Semmel on 09/19/2014 07:55 pm
I talked today to a colleague who is working on the stray-light issue of Gaia. It appears to be cyclic with 6 hours period, which is the rotation period of Gaia. But if I understood correctly, Gaia is rotating in a different plane for the commissioning, than for science operation. Whether or not it is already rotating in the science orientation, I don't know.
It appears to be still unknown what exactly the source of the stray light is. It is not uniform on the detectors, but one side of the detector array is significantly more effected than most of the area of the detector array. The structure appears to be fairly regular and consistent with the rotation period of Gaia. Therefore, it might be possible (but not certain) that the flux of the stray light can be subtracted almost perfectly from the images, but that the remaining additional photon noise will still reduce the signal to noise value of the science operations.
Title: Re: ESA - Gaia updates
Post by: denis on 09/22/2014 08:07 pm
I talked today to a colleague who is working on the stray-light issue of Gaia. It appears to be cyclic with 6 hours period, which is the rotation period of Gaia. But if I understood correctly, Gaia is rotating in a different plane for the commissioning, than for science operation. Whether or not it is already rotating in the science orientation, I don't know.
Gaia is following its nominal scan law (the one for the main mission) since end of August (26th I think).
However, any scan law it follows (nominal or the ecliptic one used for commissioning) normally keeps the rotation axis at 45deg from the Sun which seems to be what matters for this stray light issue (i.e. during commissioning they tried at lower angle to check the impact).

What's interesting is that, according to their twitter account, they are now trying down to magnitude 20.5 (normally, min magnitude is 20), which means they can still explore at faint magnitude even with this unexpected background level.
Title: Re: ESA - Gaia updates
Post by: Semmel on 09/29/2014 07:28 pm
What's interesting is that, according to their twitter account, they are now trying down to magnitude 20.5 (normally, min magnitude is 20), which means they can still explore at faint magnitude even with this unexpected background level.

That makes sense from what I know. Unfortunately I don't have any details because my source is not involved in this procedure. However, I can give some background from what I know.  I saw a straylight map that I am not allowed to make public. It shows that only parts of the scanning CCDs were effected by the background. Gaia is not only limited in the brightness, but also in the number of targets it can process. There is an algorithm on the satellite that selects the most interesting targets, stores them, queues them for transmission and begins to overwrite less interesting targets once they run out of memory. How that selection function works, I dont know.

Here comes speculation on my part: I assume the selection function somehow weights the targets according to their signal to noise. That means that bright targets <20mag on the noisy part of the CCDs have similar signal to noise as dark targets >20mag on the clean part of the CCDs. So the selection function might prioritize darker targets on the unaffected parts of CCDs over bright targets on the affected parts. And so the new magnitude limit of 20.5 makes sense. Remember: speculation from me!
Title: Re: ESA - Gaia updates
Post by: denis on 09/29/2014 10:59 pm
What's interesting is that, according to their twitter account, they are now trying down to magnitude 20.5 (normally, min magnitude is 20), which means they can still explore at faint magnitude even with this unexpected background level.

That makes sense from what I know. Unfortunately I don't have any details because my source is not involved in this procedure. However, I can give some background from what I know.  I saw a straylight map that I am not allowed to make public. It shows that only parts of the scanning CCDs were effected by the background. Gaia is not only limited in the brightness, but also in the number of targets it can process. There is an algorithm on the satellite that selects the most interesting targets, stores them, queues them for transmission and begins to overwrite less interesting targets once they run out of memory. How that selection function works, I dont know.

Here comes speculation on my part: I assume the selection function somehow weights the targets according to their signal to noise. That means that bright targets <20mag on the noisy part of the CCDs have similar signal to noise as dark targets >20mag on the clean part of the CCDs. So the selection function might prioritize darker targets on the unaffected parts of CCDs over bright targets on the affected parts. And so the new magnitude limit of 20.5 makes sense. Remember: speculation from me!

That might be possible, I don't remember how this selection is done and maybe have never known, the on-board algorithms for processing the payload data is very complex (I worked some years ago on Gaia, not on the payload but on something linked to it).

Your idea sounds plausible, but I'm not sure if increasing from 20 to 20.5 would actually lead to memory overflow. Down to mag 20, it's sized to have enough space as long as ground contact is done at the required frequency (8H per day) and there is certainly margins on that (although I admit I don't know how much), especially now (it must be sized for end-of-life, taking into account partial failure, i.e. part of the mass-memory killed by radiation). In any case, even by going from mag 20 to 20.5, the on-board memory could probably overflow only when scanning the densest parts of the sky. (although I admit I'm also a bit speculating here!)

To be honest, I can imagine that they would have tried to go to 20.5 even without the straylight issue, just to try to get the most out of the mission (even if it means at some times the mass-memory is full and the faintest stars are overwritten). It's also why they explored the bright stars limit and apparently will now be able to measure all stars (when initially the brightest stars could not be measured).
Title: Re: ESA - Gaia updates
Post by: denis on 11/16/2014 01:31 am
Image of the week - OMEGA CENTAURI AS SEEN BY GAIA - 13/11/2014

The figure is an artificial representation of the "sky" seen by Gaia when passing through the Omega Centauri globular cluster. The dots in the figure show the positions where cameras of Gaia have detected and measured stars in one pass. The seven Video Processing Units (VPUs) running the automatic image handling algorithm on-board extract around separately detected stars small windows, which are sent down to the Earth. The size and brightness of each dot is proportional to the brightness measured for each star, so overall it gives a realistic idea of the actual sky.

In this case, despite observing a region 15,800 light-years away (4,850 parsecs), in about a minute Gaia was able to detect and measure over 137 thousand stars, sending all their information to the ground segment where the Data Processing and Analysis Consortium (DPAC) systems were eager to process all these precious data.

[...]

http://www.cosmos.esa.int/web/gaia/iow_20141113 (http://www.cosmos.esa.int/web/gaia/iow_20141113)


credits: ESA/Gaia/DPAC/UB/IEEC
Title: Re: ESA - Gaia updates
Post by: bolun on 01/19/2015 08:39 pm
A year on-station for Gaia

http://blogs.esa.int/rocketscience/2015/01/14/a-year-on-station-for-gaia/
Title: Re: ESA - Gaia updates
Post by: Star One on 01/19/2015 08:50 pm
A year on-station for Gaia

http://blogs.esa.int/rocketscience/2015/01/14/a-year-on-station-for-gaia/
Glad to hear they've resolved the stray light problem.
Title: Re: ESA - Gaia updates
Post by: bolun on 07/03/2015 01:02 pm
Stellar density map - annotated

The outline of our Galaxy, the Milky Way, and of its neighbouring Magellanic Clouds, in an image based on housekeeping data from ESA’s Gaia satellite, indicating the total number of stars detected every second in each of the satellite's fields of view.

Brighter regions indicate higher concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed.

The plane of the Milky Way, where most of the Galaxy’s stars reside, is evidently the brightest portion of this image, running horizontally and especially bright at the centre. Darker regions across this broad strip of stars, known as the Galactic Plane, correspond to dense, interstellar clouds of gas and dust that absorb starlight along the line of sight.

The Galactic Plane is the projection on the sky of the Galactic disc, a flattened structure with a diameter of about 100 000 light-years and a vertical height of only 1000 light-years.

Beyond the plane, only a few objects are visible, most notably the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, which stand out in the lower right part of the image. A few globular clusters – large assemblies up to millions of stars held together by their mutual gravity – are also sprinkled around the Galactic Plane and are highlighted in this image.

http://www.esa.int/spaceinimages/Images/2015/07/Stellar_density_map_-_annotated

Related article:

- Counting stars with Gaia

http://www.esa.int/Our_Activities/Space_Science/Gaia/Counting_stars_with_Gaia

Credit:ESA/Gaia – CC BY-SA 3.0 IGO
Title: Re: ESA - Gaia updates
Post by: bolun on 08/26/2015 09:12 am
Gaia's first year of scientific observations

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_s_first_year_of_scientific_observations
Title: Re: ESA - Gaia updates
Post by: Star One on 08/26/2015 04:36 pm
I can't wait to see the intermediary results. I am assuming the stray light problem is no longer an issue.
Title: Re: ESA - Gaia updates
Post by: denis on 08/28/2015 06:15 pm
I can't wait to see the intermediary results. I am assuming the stray light problem is no longer an issue.

Neither can I!
The stray light problem is still there (there is nothing that can be done to remove it), but affects mostly the Radial Velocity Spectrometer and less so the astrometry and photometry measurements. For the RVS, they have tweaked a bit the on-board software to try to limit the impact, but they are going to measure less stars than anticipated.
For the main instrument (astrometry), it's probably not too bad as they are actually going down to magnitude 20.5 instead of 20, but possibly it's a bit noisier than expected (for some aspects, this could be compensated by a mission extension, assuming the spacecraft is fine after the nominal one).

Title: Re: ESA - Gaia updates
Post by: philw1776 on 08/28/2015 06:26 pm
Anyone know if the summer 2016 release will have items such as the distance to the Hyades cluster & to standard candles like well known Cepheids so that metrics like the Hubble constant and stellar evolutionary models can be better calibrated?
Title: Re: ESA - Gaia updates
Post by: denis on 08/28/2015 06:37 pm
Anyone know if the summer 2016 release will have items such as the distance to the Hyades cluster & to standard candles like well known Cepheids so that metrics like the Hubble constant and stellar evolutionary models can be better calibrated?

There is a Data release scenario on ESA's website:
http://www.cosmos.esa.int/web/gaia/release

Assuming this is still up-to-date, we'll have to wait for early2017 for distances:

Quote
First release: summer 2016   
 Potentially, the catalogue will be consisting of:

- Positions (α, δ) and G-magnitudes for all stars with acceptable formal standard errors of positions. For this release, it is assumed that at least 90% of the sky can be covered. The release is for all objects with single-star behavior.
...

Quote
Second release: early 2017   
Potentially, the catalogue will be consisting of:

- Five-parameter astrometric solutions of objects with single-star behavior will be released under the assumption that at least 90% of the sky can be covered.
...
Title: Re: ESA - Gaia updates
Post by: Star One on 08/28/2015 08:12 pm
Thanks for that link. So no exo-planet list until 2022.
Title: Re: ESA - Gaia updates
Post by: denis on 08/28/2015 08:56 pm
Thanks for that link. So no exo-planet list until 2022.

Maybe. It's all TBC. I guess it could change one way or another, depending on how the data processing goes (2022 is 3 years after end of nominal mission)
Title: Re: ESA - Gaia updates
Post by: Burninate on 08/28/2015 11:53 pm
Thanks for that link. So no exo-planet list until 2022.
Data releases will proceed year by year to build a better astrometric picture of the galaxy.  SNR will be very low to start with, it's only with successive observations that a better picture is built up.  Strong bias in this observation program towards nearer stars, larger planets, and longer periods.
http://arxiv.org/pdf/1411.1173v1.pdf
Title: Re: ESA - Gaia updates
Post by: bolun on 11/04/2015 05:04 pm
Rosetta comet seen by Gaia

A Gaia image of Comet 67P/Churyumov–Gerasimenko, obtained on 14 September 2015.

At that time, the ESA Rosetta spacecraft was about 300 km from the nucleus of the comet, while Gaia was over 260 million kilometres away. The comet had reached the closest point to the Sun on its orbit about a month earlier, on 13 August.

The image shows the comet’s coma and tail. The nucleus and Rosetta, which was some 300 km from the surface at the time, are both hidden in the innermost pixel. A number of background stars are also sprinkled around the image, which measures about 4.5 arc minutes across – about one-seventh of the Moon’s diameter.

Related article: Celebrity comet spotted among Gaia's stars (http://www.esa.int/Our_Activities/Space_Science/Gaia/Celebrity_comet_spotted_among_Gaia_s_stars)

http://www.esa.int/spaceinimages/Images/2015/11/Rosetta_comet_seen_by_Gaia

Image credit: ESA/Gaia/DPAC. Acknowledgement: F. Mignard & P. Tanga, Observatoire de la Côte d’Azur, France
Title: Re: ESA - Gaia updates
Post by: philw1776 on 01/11/2016 09:05 pm
Any info on 1st catalog release date set in 2016?
Any informed speculation?
And finally what content would the 1st catalog contain?
Title: Re: ESA - Gaia updates
Post by: as58 on 01/11/2016 09:45 pm
Any info on 1st catalog release date set in 2016?
Any informed speculation?
And finally what content would the 1st catalog contain?

The link to the official data release scenario is http://www.cosmos.esa.int/web/gaia/release.  The scenario tells what to expect and when. I don't know anything more about the exact date for the first release and it may not have been even decided yet. There's a big European astronomy conference in early July, so maybe they're planning to release something there.

There has been a recent addition to the first release, according to the current plans it'll include the five-parameter astrometric solution (position, proper motion and parallax) for stars in the Hipparcos Tycho-2 catalogue (~2.5 million stars with m~<11.5)
Title: Re: ESA - Gaia updates
Post by: bolun on 06/29/2016 10:33 am
Keeping Gaia’s memory (video)

http://www.esa.int/spaceinvideos/Videos/2016/06/Keeping_Gaia_s_memory
Title: Re: ESA - Gaia updates
Post by: as58 on 07/04/2016 09:44 am
The first Gaia data release will be on the 14th of September.

http://sci.esa.int/gaia/58042-mark-your-calendar-gaia-data-release-set-for-14-september/
Title: ESA - Gaia updates
Post by: Star One on 07/29/2016 07:04 pm
Cross posting.

Can the Gaia mission find planet nine?

Quote
ESA’s Gaia satellite is scanning the entire sky, detecting objects as faint as 20.7 magnitudes, but Planet Nine is likely to be fainter. Even if Gaia did see it, it probably would not be immediately recognized as a Solar System object, as its apparent motion (about 0.2 arcsecs per hour) is also below the current threshold for the Gaia data processing to immediately recognize it as a moving solar system object, but large enough to cause the planet to appear as a new “star” at a different position of the sky during subsequent Gaia observations. 

But Gaia might not need to see Planet Nine to find it.

Like all massive objects, an otherwise invisible planet hiding in the outer reaches of the Solar System deforms the fabric of space-time around it, and the light from distant stars passing by the planet would be ever-so-slightly deflected.  Measuring this deflection as the hidden planet passes in front of distant stars could reveal its presence, even if the planet itself is too faint to be seen. (See the animation below.)  This temporary deflection is the less-well-known astrometric aspect of a phenomenon called microlensing, which also causes a temporary brightening of background sources (not shown in the animation).

Quote
Unfortunately it appears from their study that such a detection by Gaia is also unlikely. The expected deviation of a star’s direction for a 10 Earth mass planet at about 700 AU is incredibly tiny: about 3 milliarcsecs if the star is within 10 milliarcsecs of the planet’s position. (One milliarcsec is 1/1000 of an arcsecond, which is 1/3600 of a degree: That’s about the apparent height of Neil Armstrong standing on the Moon as seen from Earth.) Not only that, given the apparent motion of Planet Nine on the sky, such microlensing events would have a very short duration.  Essentially a star would have to be within about 10 milliarcsecs of Planet Nine at the moment that Gaia observes it.

Regardless of how Planet Nine is found (if it exists), measurements of microlensing events by the planet will likely be the only means to directly measure its mass, as any moons revolving around Planet Nine will be far too faint even for our most powerful telescopes.  And while such microlensing events might be observable with other telescopes, only Gaia will be able to provide an accurate enough map of the sky to be able to accurately foresee such microlensing events.

https://www.linkedin.com/pulse/gaia-points-planet-nine-ronald-drimmel
Title: Re: ESA - Gaia updates
Post by: hop on 08/02/2016 02:46 am
A status update on the various issues encountered after launch.
tl;dr seems to be they are being managed acceptably.

Gaia: focus, straylight and basic angle (http://arxiv.org/abs/1608.00045)
Quote
The Gaia all-sky astrometric survey is challenged by several issues affecting the spacecraft stability. Amongst them, we find the focus evolution, straylight and basic angle variations
Contrary to pre-launch expectations, the image quality is continuously evolving, during commissioning and the nominal mission. Payload decontaminations and wavefront sensor assisted refocuses have been carried out to recover optimum performance. An ESA-Airbus DS working group analysed the straylight and basic angle issues and worked on a detailed root cause analysis. In parallel, the Gaia scientists have also analysed the data, most notably comparing the BAM signal to global astrometric solutions, with remarkable agreement.
In this contribution, a status review of these issues will be provided, with emphasis on the mitigation schemes and the lessons learned for future space missions where extreme stability is a key requirement.

Some indication of the sensitivity to subtle thermal effects:
Quote
The 24 hours period was later identified as an effect of the way the downlink is operated. Even though the phased array antenna is never switched-off, the signal coding scheme changed between ground station contacts (complex signal encoding only when downlink was active). This meant the transponders consumed more power during the contacts, which are typically scheduled according to a 24 hour logic. It was decided to force signal encoding without data transmission in the antenna outside contacts (except when spacecraft ranging is needed). This action reduced the impact of the 24 hours basic variation by more than half.
Quote
The correlation with the number of stars was puzzling at first glance, due to the negligible brightness of stellar sources. However, many service module components are affected by a bigger data rate, most notably the computers and the on-board data storage. A clear correlation thus exists between e.g. VPU5 and the peak basic angle variations, giving further support to the thermoelastic hypothesis.
Title: Re: ESA - Gaia updates
Post by: redliox on 08/02/2016 05:18 am
Gaia isn't malfunctioning thermally is it?
Title: Re: ESA - Gaia updates
Post by: hop on 08/02/2016 05:40 am
Gaia isn't malfunctioning thermally is it?
The paper I quoted above provides some details of issues that were noticed in commissioning. The issues seem to be pretty well understood now, and AFIAK the impact on the final results is expected to be relatively minor.

Just another reminder that space is hard...
Title: Re: ESA - Gaia updates
Post by: as58 on 08/02/2016 05:46 am
Gaia isn't malfunctioning thermally is it?

Gaia not malfunctioning, it's just that there are some very subtle effects (for instance due to higher heat output generated by on-board computers when scanning areas of high stellar density) that were not expected. Gaia is very sensitive to such variations, but they seem to have been able to mitigate them quite well.
Title: Re: ESA - Gaia updates
Post by: baldusi on 08/03/2016 05:15 pm
When the thermal variations due to excess or reduced processing affect your stability, you know you have a reaaaaaally extreme requirement. I'm amazed at this level of sensitivity.
Title: Re: ESA - Gaia updates
Post by: jebbo on 08/17/2016 08:35 am
A new blog post on the current status and the unexpected problems they've had to overcome:

http://sci.esa.int/gaia/58135-gaia-s-second-anniversary-marked-by-successes-and-challenges/

--- Tony
Title: Re: ESA - Gaia updates
Post by: Nomadd on 08/17/2016 04:36 pm
 The positions of faint stars seems to be the biggest issue. Stray light from the edge of the shield has cut accuracy almost in half. (Planned 300 microarcseconds to 500)
 Still a whole lot better than anything else.
Title: Re: ESA - Gaia updates
Post by: jacqmans on 09/01/2016 01:04 pm
Press Release
N°29-2016

Paris, 1 September 2016

Call for media: First data release from ESA's Gaia mission 

Media representatives are invited to a briefing on the first data release of ESA's Gaia mission, an astrometry mission to map the stars of our galaxy, the Milky Way.

The media briefing is being organised by ESA at the European Space Astronomy Centre (ESAC) in Villanueva de la Cańada, Madrid, Spain, on Wednesday 14 September 2016, 11:30-13:00 CEST. Doors open at 11:00 CEST. 

Launched in December 2013, Gaia is destined to create the most accurate map yet of the Milky Way. By making accurate measurements of the positions and motions of stars in the Milky Way, it will answer questions about the origin and evolution of our
home galaxy.

The first data release, containing among other things three-dimensional positions and two-dimensional motions of a subset of two million stars, demonstrates that Gaia's measurements are as precise as planned, paving the way to create the full map of
one billion stars to be released towards the end of 2017. 

The media briefing will provide examples of the performance of the satellite and its science data and will highlight the science that can be done with this first data release.


Programme outline

11:30-11:40 - 
Alvaro Gimenez, Director of Science, ESA:
Astrometry with Gaia at the very core of ESA's Science Programme 

11:40-11:50 - 
Fred Jansen, ESA Gaia Mission Manager:
Operating at the limits of precision 

11:50-12:00 - 
Timo Prusti, ESA Gaia Project Scientist:
Gaia on the way to the most precise map of our galaxy 

12:00-12:10 - 
Anthony Brown, Gaia Data Processing and Analysis Consortium, Leiden University:
A first exploration of the Gaia sky

12:10-12:20- 
Antonella Vallenari, Gaia Data Processing and Analysis Consortium, Instituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Padua:
Gaia's view of the nearby star clusters

12:20-12:30 - 
Gisella Clementini, Gaia Data Processing and Analysis Consortium Member of Coordination Unit 7, Instituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Bologna:
Gaia and the distance ladder   

12:30-13:00 - 
Question and Answer sessions and opportunity for individual interviews

Accreditation

For accreditation, media can register at: [email protected]
Please register by 12 September.

How to get to ESAC: http://www.esa.int/About_Us/ESAC/Getting_to_ESAC

Follow online

Webstreaming

www.youtube/esa

Social media

Twitter: @esascience. Ask questions via #AskESA.
Title: Re: ESA - Gaia updates
Post by: denis on 09/02/2016 07:59 pm
Information and statistics on the first data release:

http://www.cosmos.esa.int/web/gaia/dr1 (http://www.cosmos.esa.int/web/gaia/dr1)

Link to the Gaia data archive (real data only from the 14 of Septembre):
http://gea.esac.esa.int/archive/ (http://gea.esac.esa.int/archive/)


Image credit: ESA/Gaia/DPAC.
Title: Re: ESA - Gaia updates
Post by: zubenelgenubi on 09/02/2016 11:29 pm
Information and statistics on the first data release:
re: graph
Wow!

I'm still disappointed FAME (Full-sky Astrometric Mapping Explorer) was cancelled and that USNO didn't get to fly their mission--old news.

And, we had to wait for so long after Hipparcos for the next astrometry mission.

Looking forward to September 14!
Title: Re: ESA - Gaia updates
Post by: Nilof on 09/03/2016 01:40 am
I'm interested in the real meat - what is the distance to the Pleiades star cluster? Were the Hipparcos parallax measurements indeed wrong?
Title: Re: ESA - Gaia updates
Post by: JulesVerneATV on 09/03/2016 05:39 pm
Call for media: First data release from ESA's Gaia mission
http://www.satprnews.com/2016/09/01/call-for-media-first-data-release-from-esas-gaia-mission/
Media representatives are invited to a briefing on the first data release of ESA’s Gaia mission, an astrometry mission to map the stars of our galaxy, the Milky Way

 Two years' worth of data from the European Space Agency's (ESA) Gaia spacecraft – which includes a camera with a billion pixels – is scheduled for public release on 14 September.

Gaia will give the most detailed map of the universe ever undertaken. The spacecraft, which has a camera comprised of a mosaic of 106 CCDs, is designed to pinpoint the positions, distances, motions and other properties of more than a billion stars.

It has three instruments collecting astrometric, photometric and spectroscopic data on stars in the Milky Way galaxy, as well as more distant galaxies and quasars, and nearby, but faint Solar System objects.

Located at the L2 Lagrange point, 1.5 million kilometres from Earth, Gaia surveys the entire sky as it spins on its axis. By repeatedly measuring the positions of the stars, Gaia is providing data that enables scientists to calculate their distances and motions through our Galaxy.

‘More than 50 billion focal plane transits, 110 billion photometric observations and 9.4 billion spectroscopic observations have been successfully processed to date,’ noted Fred Jansen, ESA's mission manager for Gaia.

Question and Answer Sessions and opportunity for individual interviews
Title: Re: ESA - Gaia updates
Post by: bolun on 09/12/2016 02:16 pm
Watch Gaia first data release media briefing

Livestreaming of the media briefing on the first data release from ESA’s Gaia mission will begin on 14 September at 09:30 GMT (11:30 CEST).

The media briefing will provide examples of the performance of the satellite and its science data, and will highlight the research that can be done with this first data release.

https://www.youtube.com/watch?v=5pAjvQ5uu7I

Social-media updates will be provided on Twitter: @esascience. Ask questions via #AskESA.

Last update: 12 September 2016

http://www.esa.int/Our_Activities/Space_Science/Gaia/Watch_Gaia_first_data_release_media_briefing
Title: Re: ESA - Gaia updates
Post by: bolun on 09/12/2016 08:37 pm
ESA’s Star Mapper visualisation

In 1989, ESA launched the first space mission dedicated to astrometry – the science of charting the sky. The satellite was named Hipparcos, echoing the name of ancient Greek astronomer, Hipparchus, who compiled the oldest known stellar catalogue in the second century BC.

Hipparcos operated for over three years and a catalogue based on its data, released in 1997, had a major impact on many areas of astronomy research.

This catalogue listed 117 955 stars, reporting their positions with unprecedented accuracy, alongside estimates of their distance from us and motions through the Galaxy. It was a huge advance on the best catalogues compiled from ground-based observations, which contained information for just over 8000 stars.

The newly launched ESA Star Mapper visualisation is an exploration of some central aspects of astrometric star catalogues, using data from ESA’s Hipparcos mission.

This interactive experience allows users to delve into this famous dataset, exploring the three-dimensional distribution of almost 60 000 stars from the Hipparcos Catalogue. Stars are visualised as a function of their brightness; it is also possible to show their colours, as well as names and parent constellations for the brightest stars.

Users can get a sense of where in the sky stars were located in the past – or will be in the future – based on their motions measured by Hipparcos.

A visualisation of the ‘Hertzsprung-Russell diagram’, a tool used by astronomers to study the evolution of stars, is provided as well.

The next great breakthrough in this field will come with ESA’s Gaia mission, launched in 2013. Gaia will make a census of more than a billion stars – roughly 1% of the content of our Galaxy – of such superb precision and detail that it will revolutionise astronomy again.

The journey starts at: http://sci.esa.int/star_mapper/

More about Hipparcos: http://sci.esa.int/hipparcos/

http://www.esa.int/spaceinimages/Images/2016/09/ESA_s_Star_Mapper_visualisation

Image credit: ESA
Title: Re: ESA - Gaia updates
Post by: as58 on 09/14/2016 10:57 am
I'm interested in the real meat - what is the distance to the Pleiades star cluster? Were the Hipparcos parallax measurements indeed wrong?

If I understood correctly, new Gaia estimate disagrees with Hipparcos and agrees with the other estimates.
Title: Re: ESA - Gaia updates
Post by: Star One on 09/14/2016 11:33 am

GAIA'S BILLION-STAR MAP HINTS AT TREASURES TO COME

13 September 2016
The first catalogue of more than a billion stars from ESA's Gaia satellite was published today – the largest all-sky survey of celestial objects to date.
 
Gaia's first sky map. Credit: ESA/Gaia/DPAC. Acknowledgement: A. Moitinho & M. Barros (CENTRA – University of Lisbon), F. Mignard (Observatoire de la Côte d'Azur), on behalf of DPAC.
On its way to assembling the most detailed 3D map ever made of our Milky Way galaxy, Gaia has pinned down the precise position on the sky and the brightness of 1142 million stars.
As a taster of the richer catalogue to come in the near future, today's release also features the distances and the motions across the sky for more than two million stars.

Gaia's first sky map, annotated.
"Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before," says Alvaro Giménez, ESA's Director of Science.
"Today's release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy."
Launched 1000 days ago, Gaia started its scientific work in July 2014. This first release is based on data collected during its first 14 months of scanning the sky, up to September 2015.
"The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations," says Timo Prusti, Gaia project scientist at ESA.
The stripes and other artefacts in the image reflect how Gaia scans the sky, and will gradually fade as more scans are made during the five-year mission.

Gaia scanning the sky. Click here for details and large versions of the video. Credit: ESA/Gaia/DPAC. Acknowledgement: B. Holl (University of Geneva, Switzerland), A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC.
"The satellite is working well and we have demonstrated that it is possible to handle the analysis of a billion stars. Although the current data are preliminary, we wanted to make them available for the astronomical community to use as soon as possible," adds Dr Prusti.
Transforming the raw information into useful and reliable stellar positions to a level of accuracy never possible before is an extremely complex procedure, entrusted to a pan-European collaboration of about 450 scientists and software engineers: the Gaia Data Processing and Analysis Consortium, or DPAC.
"Today's release is the result of a painstaking collaborative work over the past decade," says Anthony Brown from Leiden University in the Netherlands, and consortium chair.
"Together with experts from a variety of disciplines, we had to prepare ourselves even before the start of observations, then treated the data, packaged them into meaningful astronomical products, and validated their scientific content."
In addition to processing the full billion-star catalogue, the scientists looked in detail at the roughly two million stars in common between Gaia's first year and the earlier Hipparcos and Tycho-2 Catalogues, both derived from ESA's Hipparcos mission, which charted the sky more than two decades ago.
By combining Gaia data with information from these less precise catalogues, it was possible to start disentangling the effects of 'parallax' and 'proper motion' even from the first year of observations only. Parallax is a small motion in the apparent position of a star caused by Earth's yearly revolution around the Sun and depends on a star's distance from us, while proper motion is due to the physical movement of stars through the Galaxy.
In this way, the scientists were able to estimate distances and motions for the two million stars spread across the sky in the combined Tycho–Gaia Astrometric Solution, or TGAS.
This new catalogue is twice as precise and contains almost 20 times as many stars as the previous definitive reference for astrometry, the Hipparcos Catalogue.
As part of their work in validating the catalogue, DPAC scientists have conducted a study of open stellar clusters – groups of relatively young stars that were born together – that clearly demonstrates the improvement enabled by the new data.

From the Solar System to the Hyades cluster. Click here for details and large versions of the video. Credit: ESA/Gaia/DPAC. Acknowledgement: T. Sagristŕ Sellés & S. Jordan (Zentrum für Astronomie der Universität Heidelberg)
"With Hipparcos, we could only analyse the 3D structure and dynamics of stars in the Hyades, the nearest open cluster to the Sun, and measure distances for about 80 clusters up to 1600 light-years from us," says Antonella Vallenari from the Istituto Nazionale di Astrofisica (INAF) and the Astronomical Observatory of Padua, Italy.
"But with Gaia's first data, it is now possible to measure the distances and motions of stars in about 400 clusters up to 4800 light-years away.
"For the closest 14 open clusters, the new data reveal many stars surprisingly far from the centre of the parent cluster, likely escaping to populate other regions of the Galaxy."
Many more stellar clusters will be discovered and analysed in even greater detail with the extraordinary data that Gaia continues to collect and that will be released in the coming years.
The new stellar census also contains 3194 variable stars, stars that rhythmically swell and shrink in size, leading to periodic brightness changes.
Many of the variables seen by Gaia are in the Large Magellanic Cloud, one of our galactic neighbours, a region that was scanned repeatedly during the first month of observations, allowing accurate measurement of their changing brightness.
Details about the brightness variations of these stars, 386 of which are new discoveries, are published as part of today's release, along with a first study to test the potential of the data.
"Variable stars like Cepheids and RR Lyraes are valuable indicators of cosmic distances," explains Gisella Clementini from INAF and the Astronomical Observatory of Bologna, Italy.
"While parallax is used to measure distances to large samples of stars in the Milky Way directly, variable stars provide an indirect, but crucial step on our 'cosmic distance ladder', allowing us to extend it to faraway galaxies."
This is possible because some kinds of variable stars are special. For example, in the case of Cepheid stars, the brighter they are intrinsically, the slower their brightness variations. The same is true for RR Lyraes when observed in infrared light. The variability pattern is easy to measure and can be combined with the apparent brightness of a star to infer its true brightness.
This is where Gaia steps in: in the future, scientists will be able to determine very accurate distances to a large sample of variable stars via Gaia's measurements of parallaxes. With those, they will calibrate and improve the relation between the period and brightness of these stars, and apply it to measure distances beyond our Galaxy. A preliminary application of data from the TGAS looks very promising.
"This is only the beginning: we measured the distance to the Large Magellanic Cloud to test the quality of the data, and we got a sneak preview of the dramatic improvements that Gaia will soon bring to our understanding of cosmic distances," adds Dr Clementini.
Knowing the positions and motions of stars in the sky to astonishing precision is a fundamental part of studying the properties and past history of the Milky Way and to measure distances to stars and galaxies, but also has a variety of applications closer to home – for example, in the Solar System.

Pluto occultation. Credit: B. Sicardy (LESIA, Observatoire de Paris, France), P. Tanga (Observatoire de la Côte d'Azur, Nice, France), A. Carbognani (Osservatorio Astronomico Valle d'Aosta, Italy), Rodrigo Leiva (LESIA, Observatoire de Paris)
In July, Pluto passed in front of a distant, faint star, offering a rare chance to study the atmosphere of the dwarf planet as the star gradually disappeared and then reappeared behind Pluto.
This stellar occultation was visible only from a narrow strip stretching across Europe, similar to the totality path that a solar eclipse lays down on our planet's surface. Precise knowledge of the star's position was crucial to point telescopes on Earth, so the exceptional early release of the Gaia position for this star, which was 10 times more precise than previously available, was instrumental to the successful monitoring of this rare event.
Early results hint at a pause in the puzzling pressure rise of Pluto's tenuous atmosphere, something that has been recorded since 1988 in spite of the dwarf planet moving away from the Sun, which would suggest a drop in pressure due to cooling of the atmosphere.
"These three examples demonstrate how Gaia's present and future data will revolutionise all areas of astronomy, allowing us to investigate our place in the Universe, from our local neighbourhood, the Solar System, to Galactic and even grander, cosmological scales," explains Dr Brown.
This first data release shows that the mission is on track to achieve its ultimate goal: charting the positions, distances, and motions of one billion stars – about 1% of the Milky Way's stellar content – in three dimensions to unprecedented accuracy.
"The road to today has not been without obstacles: Gaia encountered a number of technical challenges and it has taken an extensive collaborative effort to learn how to deal with them," says Fred Jansen, Gaia mission manager at ESA.
"But now, 1000 days after launch and thanks to the great work of everyone involved, we are thrilled to present this first dataset and are looking forward to the next release, which will unleash Gaia's potential to explore our Galaxy as we've never seen it before."
NOTES FOR EDITORS
The data from Gaia's first release can be accessed at http://archives.esac.esa.int/gaia
The content of this first release was presented today during a media briefing at ESA's European Space Astronomy Centre (ESAC) in Villanueva de la Cańada, Madrid, Spain.
Fifteen scientific papers describing the data contained in the release and their validation process will appear in a special issue of Astronomy & Astrophysics.
Gaia is an ESA mission to survey one billion stars in our Galaxy and local galactic neighbourhood in order to build the most precise 3D map of the Milky Way and answer questions about its structure, origin and evolution.
A large pan-European team of expert scientists and software developers, the Data Processing and Analysis Consortium, located in and funded by many ESA member states, is responsible for the processing and validation of Gaia's data, with the final objective of producing the Gaia Catalogue. Scientific exploitation of the data will only take place once they are openly released to the community.
Members of the consortium come from 20 European countries (Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Netherlands, Poland, Portugal, Slovenia, Spain, Switzerland, Sweden and the UK) as well as from further afield (Algeria, Brazil, Israel and the US).
In addition, ESA makes a significant contribution to the consortium in the form of the Data Processing Centre at ESAC, which, among other tasks and responsibilities, acts as the central hub for all Gaia data processing.
FOR FURTHER INFORMATION, PLEASE CONTACT:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: [email protected]
Timo Prusti
Gaia Project Scientist
European Space Agency
Email: [email protected]
Anthony Brown
Leiden Observatory, Leiden University
Leiden, The Netherlands
Email: [email protected]
Antonella Vallenari
INAF and Astronomical Observatory of Padua, Italy
Email: [email protected]
Gisella Clementini
INAF and Astronomical Observatory of Bologna, Italy
Email: [email protected]
Fred Jansen
Gaia mission manager
European Space Agency
Email: [email protected]

Last Update: 14 September 2016
Title: Re: ESA - Gaia updates
Post by: bolun on 09/14/2016 08:35 pm
Gaia's first sky map, annotated

An all-sky view of stars in our Galaxy – the Milky Way – and neighbouring galaxies, based on the first year of observations from ESA's Gaia satellite, from July 2014 to September 2015.

This map shows the density of stars observed by Gaia in each portion of the sky. Brighter regions indicate denser concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed.

The Milky Way is a spiral galaxy, with most of its stars residing in a disc about 100 000 light-years across and about 1000 light-years thick. This structure is visible in the sky as the Galactic Plane – the brightest portion of this image –which runs horizontally and is especially bright at the centre.

Darker regions across the Galactic Plane correspond to dense clouds of interstellar gas and dust that absorb starlight along the line of sight.

Many globular and open clusters – groupings of stars held together by their mutual gravity – are also sprinkled across the image.

Globular clusters, large assemblies of hundreds of thousands to millions of old stars, are mainly found in the halo of the Milky Way, a roughly spherical structure with a radius of about 100 000 light-years, and so are visible across the image.
Open clusters are smaller assemblies of hundreds to thousands of stars and are found mainly in the Galactic Plane.

The two bright objects in the lower right of the image are the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way. Other nearby galaxies are also visible, most notably Andromeda (also known as M31), the largest galactic neighbour to the Milky Way, in the lower left of the image. Below Andromeda is its satellite, the Triangulum galaxy (M33).

A number of artefacts are also visible on the image. These curved features and darker stripes are not of astronomical origin but rather reflect Gaia's scanning procedure. As this map is based on observations performed during the mission's first year, the survey is not yet uniform across the sky.

These artefacts will gradually disappear as more data are gathered during the five-year mission.

High resolution versions of the Gaia map, without annotation and with a transparent background, are available to download from: http://sci.esa.int/gaia/58209

http://sci.esa.int/gaia/58281-gaia-s-first-sky-map-annotated/

Image credit: ESA/Gaia/DPAC

Acknowledgement: A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC
Title: Re: ESA - Gaia updates
Post by: jgoldader on 09/14/2016 10:39 pm
Looks like a nice data set.  I was hoping they'd show a color-magnitude diagram or two, but the Cepheid & RR Lyrae P-L plots were nice.  I bet there's quite a race on right now by different groups to get the first papers on arXiv.
Title: Re: ESA - Gaia updates
Post by: denis on 09/15/2016 12:01 am
Looks like a nice data set.  I was hoping they'd show a color-magnitude diagram or two, but the Cepheid & RR Lyrae P-L plots were nice.  I bet there's quite a race on right now by different groups to get the first papers on arXiv.

You mean a H-R diagram ? I think they showed one during the press conference but haven't seen it on the website
Title: Re: ESA - Gaia updates
Post by: Mongo62 on 09/15/2016 12:24 am
Looks like a nice data set.  I was hoping they'd show a color-magnitude diagram or two, but the Cepheid & RR Lyrae P-L plots were nice.  I bet there's quite a race on right now by different groups to get the first papers on arXiv.

This didn't take long...

Accurate, Empirical Radii and Masses of Planets with Gaia Parallaxes (http://arxiv.org/abs/1609.04389)

We present new, empirical measurements of the radii of 132 stars that host transiting planets. These stellar radii are determined using only direct observables---the bolometric flux at Earth, the stellar effective temperature, and the parallax newly provided by the Gaia first data release---and thus are virtually model independent, extinction being the only free parameter. We also determine each star's mass using our newly determined radius and the stellar density, itself a virtually model independent quantity from the previously published transit analysis. The newly determined stellar radii and masses are in turn used to re-determine the transiting planet radii and masses, once again using only direct observables. The uncertainties on the stellar radii and masses are typically 7% and 25%, respectively, and the resulting uncertainties on the planet radii and masses are 8% and 20%, respectively. These accuracies are generally larger than the previously published model-dependent precisions of 5% and 6% on the planet radii and masses, respectively, but the newly determined values are purely empirical. We additionally report stellar radii for 366 stars that host radial-velocity (non-transiting) planets, with a typical achieved accuracy in the radii of 3%. Most importantly, the stellar bolometric fluxes and angular radii reported here---with typical accuracies of 2% and 3%, respectively---will serve as a fundamental data set to permit the re-determination of the planet radii and masses with the Gaia second data release to 3% and 7% accuracy, comparable to or better than currently published precisions, but in an entirely empirical fashion.
Title: Re: ESA - Gaia updates
Post by: Galactic Penguin SST on 09/15/2016 01:37 am
Is there any place where the figures are presented in an easy to view format (distance in light years, star type etc.)? I have been waiting for this day to re-ignite my interest in star population census.  ;) (e.g. Can Eta Carinae keep the title of one of the galaxy's most bright stars?)
Title: Re: ESA - Gaia updates
Post by: CuddlyRocket on 09/15/2016 04:30 am
Is there any place where the figures are presented in an easy to view format (distance in light years, star type etc.)?

You'll be lucky! Although ESA is playing lip-service to the idea of public engagement and for members of the public to search the database to find items of interest, they don't appear to have actually done anything to facilitate same.

There is a search page (http://gea.esac.esa.int/archive/), the use of which is presumably self-evident to professional astronomers etc, but which is far from clear to me, and possibly most laymen. There's no how-to-use guide available, for instance. Or at least I couldn't find one! Given BBC news showed some schoolchildren who found a supernova, it's presumably not that difficult to use once you know how. Was there some material given to teachers by ESA, or did this school just happen to have contact with somehow who's familiar with such database search engines? A local university outreach perhaps?

This follows the frankly dire media presentation. ESA is notoriously poor at public outreach compared to NASA; this could be down to budgets, but I suspect it's because the individuals involved don't care that much.
Title: Re: ESA - Gaia updates
Post by: Stan-1967 on 09/15/2016 04:53 am
Is there any place where the figures are presented in an easy to view format (distance in light years, star type etc.)?

You'll be lucky! Although ESA is playing lip-service to the idea of public engagement and for members of the public to search the database to find items of interest, they don't appear to have actually done anything to facilitate same.

There is a search page (http://gea.esac.esa.int/archive/), the use of which is presumably self-evident to professional astronomers etc, but which is far from clear to me, and possibly most laymen. There's no how-to-use guide available, for instance. Or at least I couldn't find one! Given BBC news showed some schoolchildren who found a supernova, it's presumably not that difficult to use once you know how. Was there some material given to teachers by ESA, or did this school just happen to have contact with somehow who's familiar with such database search engines? A local university outreach perhaps?

This follows the frankly dire media presentation. ESA is notoriously poor at public outreach compared to NASA; this could be down to budgets, but I suspect it's because the individuals involved don't care that much.

You can use the search feature using identifiers from the Kepler Input Catalog.   I suspect it also works with the Hipparcos catalog.   You should find a column listing the parallax in milliarc seconds.  You have to convert that to parsec or light years.   I tried it for KIC 8462852, but couldn't get my conversion to match what was on reddit.  It's definately not friendly.  Par for the course when dealing with ESA.
Title: Re: ESA - Gaia updates
Post by: Star One on 09/15/2016 05:57 am
Is there any place where the figures are presented in an easy to view format (distance in light years, star type etc.)?

You'll be lucky! Although ESA is playing lip-service to the idea of public engagement and for members of the public to search the database to find items of interest, they don't appear to have actually done anything to facilitate same.

There is a search page (http://gea.esac.esa.int/archive/), the use of which is presumably self-evident to professional astronomers etc, but which is far from clear to me, and possibly most laymen. There's no how-to-use guide available, for instance. Or at least I couldn't find one! Given BBC news showed some schoolchildren who found a supernova, it's presumably not that difficult to use once you know how. Was there some material given to teachers by ESA, or did this school just happen to have contact with somehow who's familiar with such database search engines? A local university outreach perhaps?

This follows the frankly dire media presentation. ESA is notoriously poor at public outreach compared to NASA; this could be down to budgets, but I suspect it's because the individuals involved don't care that much.

You can use the search feature using identifiers from the Kepler Input Catalog.   I suspect it also works with the Hipparcos catalog.   You should find a column listing the parallax in milliarc seconds.  You have to convert that to parsec or light years.   I tried it for KIC 8462852, but couldn't get my conversion to match what was on reddit.  It's definately not friendly.  Par for the course when dealing with ESA.

Look on the Twitter feed of Jason Wright for conversion to light years for that particular star.
Title: Re: ESA - Gaia updates
Post by: as58 on 09/15/2016 07:08 am
You can use the search feature using identifiers from the Kepler Input Catalog.   I suspect it also works with the Hipparcos catalog.   You should find a column listing the parallax in milliarc seconds.  You have to convert that to parsec or light years.   I tried it for KIC 8462852, but couldn't get my conversion to match what was on reddit.  It's definately not friendly.  Par for the course when dealing with ESA.

Distance in parsecs is just 1 divided by parallax in arcseconds, so dividing one by the parallax in milliarcseconds gives distance in kiloparsecs (This is actually pretty much the definition of parsec. Even the name comes from parallax second). To get the distance in lightyears, multiply the distance in parsecs by about 3.26.

The search works with pretty much any name for a star (various catalogue numbers, Bayer designation, proper name etc.). Note however that there is no data for the brightest stars, so there are not many (any?) stars with a proper name included. The search will still resolve the name, but there is no data returned.
Title: Re: ESA - Gaia updates
Post by: Star One on 09/15/2016 07:55 am
Are systematic errors those errors introduced into the results by Gaia itself?
Title: Re: ESA - Gaia updates
Post by: as58 on 09/15/2016 08:30 am
Are systematic errors those errors introduced into the results by Gaia itself?

No, the parallax error listed in the database doesn't include the systematic error. This is said clearly in, for instance, the main paper (http://www.aanda.org/articles/aa/pdf/forth/aa29512-16.pdf) presenting the data release (near the beginning of section 3):

Quote
The typical uncertainty for the parallaxes is 0.3 mas, where it should be noted that a systematic component of 0.3 mas should be added (see Sect. 6).
Title: Re: ESA - Gaia updates
Post by: Star One on 09/15/2016 08:46 am
Are systematic errors those errors introduced into the results by Gaia itself?

No, the parallax error listed in the database doesn't include the systematic error. This is said clearly in, for instance, the main paper (http://www.aanda.org/articles/aa/pdf/forth/aa29512-16.pdf) presenting the data release (near the beginning of section 3):

Quote
The typical uncertainty for the parallaxes is 0.3 mas, where it should be noted that a systematic component of 0.3 mas should be added (see Sect. 6).

I've seen a number of people online criticise ESA for the failure to get across clearly matters such as this and that their public outreach leaves a lot to be desired.
Title: Re: ESA - Gaia updates
Post by: as58 on 09/15/2016 09:43 am
I've seen a number of people online criticise ESA for the failure to get across clearly matters such as this and that their public outreach leaves a lot to be desired.

I don't know about public outreach, but I don't know how they could've been more clear about the systematics. The data release page even has this sentence bolded:

Quote
The recommendation is to consider the quoted uncertainties on the parallaxes as ±σϖ (random) ±0.3 mas (systematic). Furthermore, averaging parallaxes over small regions of the sky will not reduce the uncertainty on the mean below the 0.3 mas level.

It seems that a lot of people just rushed into looking at data without bothering to read any of the release notes.
Title: Re: ESA - Gaia updates
Post by: Star One on 09/15/2016 09:56 am
I've seen a number of people online criticise ESA for the failure to get across clearly matters such as this and that their public outreach leaves a lot to be desired.

I don't know about public outreach, but I don't know how they could've been more clear about the systematics. The data release page even has this sentence bolded:

Quote
The recommendation is to consider the quoted uncertainties on the parallaxes as ±σϖ (random) ±0.3 mas (systematic). Furthermore, averaging parallaxes over small regions of the sky will not reduce the uncertainty on the mean below the 0.3 mas level.

It seems that a lot of people just rushed into looking at data without bothering to read any of the release notes.

I mean getting it across to lay people & amateur astronomers or did they think only professional astronomers were going to look at this. At least NASA tries to cater its information for the general populace, something that ESA seems particular poor at.
Title: Re: ESA - Gaia updates
Post by: Star One on 09/15/2016 05:34 pm
Further article on Gaia.

Interesting comment underneath that if it keeps going for ten years it could discover 70,000 gas giants alone.

http://www.centauri-dreams.org/?p=36391
Title: Re: ESA - Gaia updates
Post by: as58 on 09/15/2016 06:19 pm
Further article on Gaia.

Interesting comment underneath that if it keeps going for ten years it could discover 70,000 gas giants alone.

http://www.centauri-dreams.org/?p=36391

This article goes into detail on prospects of detecting exoplanets with Gaia.

 http://arxiv.org/abs/1411.1173

Abstract:
Quote


    We provide a revised assessment of the number of exoplanets that should be discovered by Gaia astrometry, extending previous studies to a broader range of spectral types, distances, and magnitudes. Our assessment is based on a large representative sample of host stars from the TRILEGAL Galaxy population synthesis model, recent estimates of the exoplanet frequency distributions as a function of stellar type, and detailed simulation of the Gaia observations using the updated instrument performance and scanning law. We use two approaches to estimate detectable planetary systems: one based on the S/N of the astrometric signature per field crossing, easily reproducible and allowing comparisons with previous estimates, and a new and more robust metric based on orbit fitting to the simulated satellite data.
    With some plausible assumptions on planet occurrences, we find that some 21,000 (+/-6000) high-mass (1-15M_J) long-period planets should be discovered out to distances of ~500pc for the nominal 5-yr mission (including at least 1000-1500 around M dwarfs out to 100pc), rising to some 70,000 (+/-20,000) for a 10-yr mission. We indicate some of the expected features of this exoplanet population, amongst them ~25-50 intermediate-period (P~2-3yr) transiting systems.
Title: Re: ESA - Gaia updates
Post by: Bubbinski on 09/15/2016 07:18 pm
Congratulations to the Gaia craft and team!

Wondering if Gaia data can confirm if Proxima b transits its star as seen from our solar system's vantage point.

Also wondering if exoplanets (large gas giants of course) will be found in the Magellanic Cloud dwarf galaxies as a result of this data. (Extragalactic exoplanets!)

Edit: I looked up the distance to the LMC after reviewing the post above mine. LMC is 50 kilo parsecs away and the arXiv article says Gaia can discover planets up to 500 parsecs away (0.5 kilo parsecs). So the answer would appear to be "no" for question 2 (no extragalactic exoplanets from Gaia)

And can this data be used to find ring systems or exomoons?
Title: ESA - Gaia updates
Post by: Star One on 09/15/2016 07:55 pm
Congratulations to the Gaia craft and team!

Wondering if Gaia data can confirm if Proxima b transits its star as seen from our solar system's vantage point.

Also wondering if exoplanets (large gas giants of course) will be found in the Magellanic Cloud dwarf galaxies as a result of this data. (Extragalactic exoplanets!)

Edit: I looked up the distance to the LMC after reviewing the post above mine. LMC is 50 kilo parsecs away and the arXiv article says Gaia can discover planets up to 500 parsecs away (0.5 kilo parsecs). So the answer would appear to be "no" for question 2 (no extragalactic exoplanets from Gaia)

And can this data be used to find ring systems or exomoons?


Hmmm you're interesting in transits of Proxima b, have a look on the Pale Red Dot Thread.
Title: Re: ESA - Gaia updates
Post by: denis on 09/15/2016 08:41 pm
Congratulations to the Gaia craft and team!
Thanks !  :P
Title: Re: ESA - Gaia updates
Post by: Hungry4info3 on 09/16/2016 12:53 am
And can this data be used to find ring systems or exomoons?

No. Gaia is using astrometry. It is sensitive to the barycentric motion of the star. It may also be sensitive to transits, but there's a lot of varying estimates on how many we should expect to detect.

Transit searches tend to be rather high-cadence, taking thousands of measurements of a star at a time. Gaia will take 70 measurements per star on average. For a short-period planet, this means three or four measurements may occur during a transit. So we're talking about, statistically, very poor quality detections even of hot Jupiters.

Dzigan and Zucker estimate hundreds to thousands of transiting exoplanets from Gaia photometry.
http://arxiv.org/abs/1205.4725

There is an analogy of this from Hipparcos, where a transit of HD 209458 b was found (with 89 photometric measurements) after the planet's RV-based discovery.
http://adsabs.harvard.edu/abs/2000A&A...355..295R

With the photometric detection of planets restricted to very short-period planets, rings and exomoons are ruled out because they aren't tidally stable (even if, somehow, they were detectable in such sparse data sets).
Title: ESA - Gaia updates
Post by: Star One on 09/20/2016 06:57 am
Evidence for a systematic offset of −0.25~mas in the Gaia DR1 parallaxes

Quote
We test the parallaxes reported in the Gaia first data release using the sample of eclipsing binaries with accurate, empirical distances from Stassun & Torres (2016). We find a clear average offset of −0.25±0.05 mas in the sense of the Gaia parallaxes being too small (i.e., the distances too long). The documented Gaia systematic uncertainty is 0.3 mas, which the eclipsing binary sample corroborates. The offset does not depend strongly on obvious parameters such as color, brightness, or spatial position. However, with a statistical significance of 99.7%, nearer stars possibly exhibit larger offsets according to Δπ≈−0.16−0.02×π mas.

http://arxiv.org/abs/1609.05390
Title: Re: ESA - Gaia updates
Post by: denis on 09/26/2016 07:50 pm
There is a search page (http://gea.esac.esa.int/archive/), the use of which is presumably self-evident to professional astronomers etc, but which is far from clear to me, and possibly most laymen. There's no how-to-use guide available, for instance. Or at least I couldn't find one! Given BBC news showed some schoolchildren who found a supernova, it's presumably not that difficult to use once you know how. Was there some material given to teachers by ESA, or did this school just happen to have contact with somehow who's familiar with such database search engines? A local university outreach perhaps?

Concerning finding supernovae, I think you are confusing with the Gaia alert page, which generates "real time" (daily basis?) alerts for objects suddenly brighter than previously measured, such as to trigger further observations and classification from ground. This is not based on the catalogue release but on this page: http://gsaweb.ast.cam.ac.uk/alerts/home


Concerning distances, from reading various tweets it seems computing distance from parallax is a complex problem and simply taking the inverse of the parallax is good only if the parallax error is small (< 1% I saw somewhere). I assume this is why DPAC provides parallax measurements and not directly distance, such that various science groups can estimate distances based on different techniques.
For example, one article concerning converting Gaia's DR1 parallaxes into distances:
https://arxiv.org/pdf/1609.07369v1.pdf

Quote
We infer distances and their asymmetric uncertainties for two million stars using the parallaxes
published in the Gaia DR1 (GDR1) catalogue.
...
except to remind readers that inverting parallaxes to estimate distances is only appropriate in the absence of
noise. As parallax measurements have uncertainties— and for many TGAS stars very large uncertainties—
distance estimation should always be treated as an inference problem.

Title: Re: ESA - Gaia updates
Post by: Star One on 09/27/2016 01:05 pm
TGAS Error Renormalization from the RR Lyrae Period-Luminosity Relation

Quote
The Gaia team has applied a renormalization to their internally-derived parallax errors σint(π)
σtgas(π)=[Aσint(π)]2+σ20−−−−−−−−−−−−−√;    (A,σ0)=(1.4,0.20 mas)
based on comparison to Hipparcos astrometry. We use a completely independent method based on the RR Lyrae K-band period-luminosity relation to derive a substantially different result, with smaller ultimate errors
(A,σ0)=(1.1,0.12 mas)    (this paper).
We argue that our estimate is likely to be more accurate and therefore that the reported TGAS parallax errors should be reduced according to the prescription:
σtrue(π)=(0.79σtgas(π))2−(0.10 mas)2−−−−−−−−−−−−−−−−−−−−−−−√.

http://arxiv.org/abs/1609.06315
Title: Re: ESA - Gaia updates
Post by: jgoldader on 09/28/2016 05:57 pm
Concerning distances, from reading various tweets it seems computing distance from parallax is a complex problem and simply taking the inverse of the parallax is good only if the parallax error is small (< 1% I saw somewhere). I assume this is why DPAC provides parallax measurements and not directly distance, such that various science groups can estimate distances based on different techniques.
For example, one article concerning converting Gaia's DR1 parallaxes into distances:
https://arxiv.org/pdf/1609.07369v1.pdf

Quote
We infer distances and their asymmetric uncertainties for two million stars using the parallaxes
published in the Gaia DR1 (GDR1) catalogue.
...
except to remind readers that inverting parallaxes to estimate distances is only appropriate in the absence of
noise. As parallax measurements have uncertainties— and for many TGAS stars very large uncertainties—
distance estimation should always be treated as an inference problem.



When Gaia measures the position of a star on the CCD, there's uncertainty in the (x,y) position due to the fitting of the centroid (with some weighting perhaps) of the PSF.  (For the moment, ignore the uncertainties in the conversion of those (x,y) positions to (RA, DEC) positions.) 

If not for proper motion, stars would just move "back and forth" on the sky due to parallax.  But all disk stars are also in motion through space, typically at ~225 km/s or so with random motions thrown in for fun, around the center of the Milky Way.  So if you measure a star from two positions in space, you'll get parallax, yes; but since the star will have moved in 3D space since your first measurement ("proper motion" is that motion projected into 2D onto the celestial sphere) the position differs not only due to parallax, but the star's own proper motion as well.  Proper motion makes the motion of the stars looks like a sort of slanted sinusoidal curve against the sky.  You must have several epochs of observations (at bare minimum several spread over one year, but two years is better) to be able to model the sine curve.  The higher the proper motion perpendicular to the parallax direction, the more "stretched out" the since curve looks (it looks like its wavelength increases); but proper motion near the direction of parallax makes the sine look like a Z that's squashed and stretched sideways.  The higher the parallax (i.e., the closer the star) the greater the amplitude of the sine curve.  (Oh, and some stars are binaries or have planets that make them have extra motions due to their companions, and...)

But in the end, you have a bunch of measurements of position, and from those you have to get the amount and direction of proper motion, plus the amount of parallax.  And the quality of your solutions for each of these depends on the quality of your position measurements.  So the uncertainty propagates through everything you do.  Hence, due to your position uncertainties (which include random---i.e., centroiding---errors, which depend in part on brightness and CCD characteristics, as well as systematics), your parallax and proper motion will also have random + systematic uncertainties. 

One of the many wonderful things about Gaia is that the teams will continue to improve the quality of the catalog as they get better at modeling systematics (e.g., thermal and outgassing effects) and accumulate more years of data.
Title: Re: ESA - Gaia updates
Post by: bolun on 11/01/2016 08:33 pm
Follow the Gaia 2016 data release #1 Workshop live

28 October 2016

On 2-4 November, the European Space Astronomy Centre near Madrid, Spain, will host the Gaia 2016 Data Release #1 Workshop. Many of the talks will be broadcast live.

Livestream: http://livestream.com/ESA/events/6544080

http://sci.esa.int/gaia/58552-follow-the-gaia-2016-data-release-1-workshop-live/
Title: Re: ESA - Gaia updates
Post by: Star One on 11/22/2016 08:19 pm
Gaia microlensing event.

http://www.cosmos.esa.int/web/gaia/IoW_20161027
Title: Re: ESA - Gaia updates
Post by: bolun on 01/27/2017 08:45 pm
Gaia turns its eyes to asteroid hunting

24 January 2017

Whilst best known for its surveys of the stars and mapping the Milky Way in three dimensions, ESA's Gaia has many more strings to its bow. Among them, its contribution to our understanding of the asteroids that litter the Solar System. Now, for the first time, Gaia is not only providing information crucial to understanding known asteroids, it has also started to look for new ones, previously unknown to astronomers.

http://sci.esa.int/gaia/58706-gaia-turns-its-eyes-to-asteroid-hunting/
Title: Re: ESA - Gaia updates
Post by: as58 on 02/08/2017 05:02 pm
There have been some changes in the data release plan. Now the next release is expected in April 2018 instead of earlier plan of Q4 2017. On the plus side, it appears (if I remember correctly) that the release will contain some data that were previously not planned for DR2.

https://www.cosmos.esa.int/web/gaia/release
Title: Re: ESA - Gaia updates
Post by: denis on 02/08/2017 08:24 pm

I find the following wording a bit strange:
Quote
The DPAC project office and ESA are working on the longer term data release schedule. The release planned at three years after the end of the nominal mission lifetime (called 'final release' below) will be maintained, while the number of releases between Gaia DR2 and the final release remains to be decided​.

Assuming no failure, the mission is likely to be extended until the spacecraft runs out of cold gas.
So does that mean they plan a 'final release' 3 years after end of nominal mission lifetime and what comes next is "extra" that will be part of a further release ?
Or is it just because they cannot formally assume there will be an extension ?
Title: Re: ESA - Gaia updates
Post by: as58 on 02/08/2017 08:46 pm
I think the 'final' release is some sort of mission success criterion. Though an extension is likely (assuming good spacecraft health etc.), they can't officially count on it until it's been formally approved.
Title: Re: ESA - Gaia updates
Post by: jebbo on 02/09/2017 11:38 am
Latest on Gaia and exoplanets:

http://sci.esa.int/gaia/58784-exoplanets/

and

https://www.cosmos.esa.int/web/gaia/iow_20170209

--- Tony
Title: Re: ESA - Gaia updates
Post by: Star One on 02/15/2017 07:05 pm
Quote
[Toronto] Using a novel method and data from the Gaia space telescope, astronomers from the University of Toronto have estimated that the speed of the Sun as it orbits the centre of the Milky Way Galaxy is approximately 240 kilometres per second.
In turn, they have used that result to calculate that the Sun is approximately 7.9 kiloparsecs from the Galaxy’s centre—or almost twenty-six thousand light-years.

Using data from the Gaia space telescope and the RAdial Velocity Experiment (RAVE) survey, Jason Hunt and his colleagues determined the velocities of over 200,000 stars relative to the Sun. Hunt is a Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics, University of Toronto.

http://www.dunlap.utoronto.ca/missing-stars-in-the-solar-neighbourhood-reveal-the-suns-speed-and-distance-to-the-centre-of-the-milky-way-galaxy/
Title: Re: ESA - Gaia updates
Post by: Star One on 03/06/2017 07:53 pm
Gaia Data Release 1. Open cluster astrometry: performance, limitations, and future prospects

Quote
Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information. Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters. Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed. Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier Hipparcos-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters. Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the Hipparcos data, with clearly increased luminosities for older A and F dwarfs.

https://arxiv.org/abs/1703.01131
Title: Re: ESA - Gaia updates
Post by: bolun on 04/13/2017 12:23 pm
Two million stars on the move

12 April 2017

The changing face of our Galaxy is revealed in a new video from ESA’s Gaia mission. The motion of two million stars is traced 5 million years into the future using data from the Tycho-Gaia Astrometric Solution, one of the products of the first Gaia data release. This provides a preview of the stellar motions that will be revealed in Gaia's future data releases, which will enable scientists to investigate the formation history of our Galaxy.

http://sci.esa.int/gaia/59004-two-million-stars-on-the-move/

https://youtu.be/Ag0qsSFJBAk
Title: Re: ESA - Gaia updates
Post by: bolun on 06/10/2017 12:51 pm
The future of the Orion constellation

9 June 2017

A new video, based on measurements by ESA’s Gaia and Hipparcos satellites, shows how our view of the Orion constellation will evolve over the next 450 000 years.

Stars are not motionless in the sky: their positions change continuously as they move through our Galaxy, the Milky Way. These motions, too slow to be appreciated with the naked eye over a human lifetime, can be captured by high-precision observations like those performed by ESA’s billion-star surveyor, Gaia.

By measuring their current movements, we can reconstruct the past trajectories of stars through the Milky Way to study the origins of our Galaxy, and even estimate stellar paths millions of years into the future.

This video provides us with a glimpse over the coming 450 000 years, showing the expected evolution of a familiar patch of the sky, featuring the constellation of Orion, the Hunter.

http://www.esa.int/Our_Activities/Space_Science/Gaia/The_future_of_the_Orion_constellation

https://youtu.be/ia0s1G8cdv0
Title: Re: ESA - Gaia updates
Post by: Ben the Space Brit on 06/11/2017 04:31 pm
That Orion one has one major bit of speculation in it: No-one knows how long Betelgeuse has left!
Title: ESA - Gaia updates
Post by: Star One on 07/08/2017 08:54 pm
Quote
With the help of software that mimics a human brain, ESA's Gaia satellite spotted six stars zipping at high speed from the centre of our Galaxy to its outskirts. This could provide key information about some of the most obscure regions of the Milky Way.

http://sci.esa.int/gaia/59263-artificial-brain-helps-gaia-catch-speeding-stars/

https://youtu.be/p2qOswM7RIo
Title: Re: ESA - Gaia updates
Post by: bolun on 08/21/2017 11:03 am
Preview of Gaia’s sky in colour

This map is a preview of Gaia’s measurements of the sky in colour.

The image includes preliminary data from 18.6 million bright stars observed by Gaia between July 2014 and May 2016, and it shows the middle value of the colours of all stars that are observed in each pixel. The colour of each star is estimated by comparing the total amount of blue and red light recorded by Gaia.

The Galactic Plane, corresponding to the most densely populated region of our Milky Way galaxy, stands out as the roughly horizontal feature across the image. The reddest regions in the map, mainly found near the Galactic Centre, correspond to dark areas in the density of stars: these are clouds of dust that obscure part of the starlight, especially at blue wavelengths, making it appear redder. It is also possible to see the two Magellanic Clouds – small satellite galaxies of our Milky Way – in the lower part of the map.

Gaia’s first full-colour all-sky map, based on data for more than 1 billion stars, will be unleashed in its highest resolution in April 2018.

Full story: Sneak peek of Gaia's sky in colour (http://sci.esa.int/gaia/59404-sneak-peek-of-gaias-sky-in-colour/)

http://www.esa.int/spaceinimages/Images/2017/08/Preview_of_Gaia_s_sky_in_colour

Image credit: ESA/Gaia/DPAC/CU5/CU8/DPCI/F. De Angeli, D.W. Evans, M. Riello, M. Fouesneau, R. Andrae, C.A.L. Bailer-Jones
Title: Re: ESA - Gaia updates
Post by: jebbo on 12/07/2017 04:16 pm
Extended to 31 Dec 2020

http://sci.esa.int/director-desk/59839-green-light-for-continued-operations-of-esa-science-missions/ (http://sci.esa.int/director-desk/59839-green-light-for-continued-operations-of-esa-science-missions/)

--- Tony
Title: Re: ESA - Gaia updates
Post by: bolun on 12/27/2017 10:35 am
Four years of Gaia (http://www.esa.int/spaceinimages/Images/2017/12/Four_years_of_Gaia)
Title: Re: ESA - Gaia updates
Post by: Star One on 01/04/2018 07:36 pm
Using GAIA to detect low frequency gravitational waves (https://www.kicc.cam.ac.uk/news/using-gaia-to-detect-low-frequency-gravitational-waves)
Title: Re: ESA - Gaia updates
Post by: jebbo on 01/25/2018 11:34 am
Quote
@ESAGaia and #DPAC are happy to announce the release date and expected contents of #GaiaDR2: https://www.cosmos.esa.int/web/gaia/dr2

https://twitter.com/ESAGaia/status/956504296715145216 (https://twitter.com/ESAGaia/status/956504296715145216)

DR2 will be 25th April 2018! 

--- Tony
Title: Re: ESA - Gaia updates
Post by: Star One on 02/28/2018 03:53 pm
Chasing a stellar flash

https://youtu.be/04O3r8hlOPQ
Title: Re: ESA - Gaia updates
Post by: bolun on 03/21/2018 08:56 pm
Gaia status update: safe mode and recovery

21 March 2018

Last month, ESA's Gaia satellite experienced a technical anomaly followed by a 'safe mode' event. After thorough examination, the spacecraft was successfully recovered and resumed normal scientific operations, while the mission team keeps investigating the exact cause of the anomaly.

http://sci.esa.int/gaia/60098-gaia-status-update-safe-mode-and-recovery/
Title: Re: ESA - Gaia updates
Post by: bolun on 04/04/2018 03:32 pm
GAIA'S VIEW OF DARK INTERSTELLAR CLOUDS

03 April 2018

While charting the positions of more than a billion stars, ESA's Gaia mission provides all-important information even about the dark patches of the sky where fewer stars are observed. These images, based on Gaia's first data release, are an appetizer to the astronomical riches that will be unleashed with the mission's second release on 25 April.

http://sci.esa.int/gaia/60131-gaia-s-view-of-dark-interstellar-clouds/
Title: Re: ESA - Gaia updates
Post by: Star One on 04/05/2018 08:23 pm
HOW MANY STARS TO EXPECT IN GAIA'S SECOND DATA RELEASE

Quote
05 April 2018

As astronomers worldwide are preparing to explore the second data release of ESA's Gaia satellite, the Data Processing and Analysing Consortium announced just how many sources will be included in the new catalogue, which will be made public on 25 April.[/quote{

http://sci.esa.int/gaia/60146-how-many-stars-to-expect-in-gaia-s-second-data-release/
Title: Re: ESA - Gaia updates
Post by: TakeOff on 04/06/2018 05:20 am
14,000 Solar system objects are expected in DR2. Could Gaia detect Oort cloud objects microlensing a background star? What kinds of Ss objects is it detecting, Main belt asteroids, or NEAs?
Title: Re: ESA - Gaia updates
Post by: jgoldader on 04/06/2018 10:23 am
14,000 Solar system objects are expected in DR2. Could Gaia detect Oort cloud objects microlensing a background star? What kinds of Ss objects is it detecting, Main belt asteroids, or NEAs?

It should be mostly main-belt asteroids, possibly NEOs, depending on how good the algorithms are that they're using to match observations of fast moving things (connecting the dots, if you will).

But a quick check shows Gaia should go down to 20th magnitude (probably in uncluttered areas only), whereas Pluto's more than 100x brighter.  So, direct detection of some big KBOs/TNOs should be possible. But Oort Cloud... I'd say unlikely, because the reflected brightness scales like 1/r^4 (inverse square both ways) so Pluto would be visible out to about 3x, maybe a little more, than its current distance.  You'd need something a lot bigger to be seen in the Oort cloud.  Microlensing would simply look to be a transient, I'd suppose.

The observing arcs should be long enough to give half decent prelim orbits for bright TNOs, could be very interesting to see what this does to statistics for the TNO orbits from which Planet 9 has been hypothesized.
Title: Re: ESA - Gaia updates
Post by: Star One on 04/06/2018 11:14 am
14,000 Solar system objects are expected in DR2. Could Gaia detect Oort cloud objects microlensing a background star? What kinds of Ss objects is it detecting, Main belt asteroids, or NEAs?

It should be mostly main-belt asteroids, possibly NEOs, depending on how good the algorithms are that they're using to match observations of fast moving things (connecting the dots, if you will).

But a quick check shows Gaia should go down to 20th magnitude (probably in uncluttered areas only), whereas Pluto's more than 100x brighter.  So, direct detection of some big KBOs/TNOs should be possible. But Oort Cloud... I'd say unlikely, because the reflected brightness scales like 1/r^4 (inverse square both ways) so Pluto would be visible out to about 3x, maybe a little more, than its current distance.  You'd need something a lot bigger to be seen in the Oort cloud.  Microlensing would simply look to be a transient, I'd suppose.

The observing arcs should be long enough to give half decent prelim orbits for bright TNOs, could be very interesting to see what this does to statistics for the TNO orbits from which Planet 9 has been hypothesized.

What about detecting Planet 9 itself?
Title: Re: ESA - Gaia updates
Post by: jgoldader on 04/06/2018 01:10 pm
What about detecting Planet 9 itself?

That's the million dollar question!  :) 

But I believe, from Brown's website, it could be 22nd mag or fainter (and 22nd magnitude is about 6 times fainter than Gaia's limit of 20th mag).  And Gaia's completeness at 20th magnitude won't be as high *in* the Galactic plane as *out* of the plane. 

My gut says Gaia probably won't see Putative Planet 9 (<50% chance), though I'd be happy to be wrong.  However, I think it's more likely Gaia will discover a good number of TNOs, and if gets a bunch of the really high semi major axis ones, those might be sufficient to make (or break) the statistical case for Planet 9.  We'll know soon!
Title: Re: ESA - Gaia updates
Post by: Star One on 04/06/2018 01:40 pm
What about detecting Planet 9 itself?

That's the million dollar question!  :) 

But I believe, from Brown's website, it could be 22nd mag or fainter (and 22nd magnitude is about 6 times fainter than Gaia's limit of 20th mag).  And Gaia's completeness at 20th magnitude won't be as high *in* the Galactic plane as *out* of the plane. 

My gut says Gaia probably won't see Putative Planet 9 (<50% chance), though I'd be happy to be wrong.  However, I think it's more likely Gaia will discover a good number of TNOs, and if gets a bunch of the really high semi major axis ones, those might be sufficient to make (or break) the statistical case for Planet 9.  We'll know soon!

So we can see a lot more of the flock but probably not the shepherd.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 04/06/2018 05:36 pm
Solar System objects were originally scheduled for Data Release 5. They brought forward more observations of 14,099 known objects: they are putting up more points in the MPC which help reduce uncertainties. I am excited over the Solar System objects myself so I have been listening to what they have been saying. One of the last images they put up before DR1 was an explanation of what they were doing about them. All of Gaia's data is important, so for points that were not associated with fixed stars they had matched several with Solar System objects. While some where good matches, some where not so good but within limits of a poorly observed object while others were moving but did not match something known. My understanding -and I do not have any inside information - is that they are releasing observations from the first type: known well understood objects. Now the Gaia dataset is HUGE and growing, they are slowly bringing online more processing flows for more objects and as they are brought online and they are happy with their quality they get released.

After they are done with stars, galaxies and solar system objects, I guess what is left is cosmic rays. Will they release cosmic ray events in the end? Is that even possible? I have no idea
Title: Re: ESA - Gaia updates
Post by: Bubbinski on 04/06/2018 07:20 pm
How many exoplanets will be in the April 25 Gaia data release?
Title: Re: ESA - Gaia updates
Post by: Star One on 04/06/2018 07:24 pm
How many exoplanets will be in the April 25 Gaia data release?

I didn’t think there would be any?
Title: Re: ESA - Gaia updates
Post by: as58 on 04/06/2018 07:49 pm
How many exoplanets will be in the April 25 Gaia data release?

I didn’t think there would be any?

Yes, no exoplanets in the next release and according to current plans, not in the one after that (in 2020) either. Detecting exoplanets with Gaia requires a long period of observations, so they will be only included in the final (prime mission) release in 2022.
Title: Re: ESA - Gaia updates
Post by: hop on 04/06/2018 07:50 pm
How many exoplanets will be in the April 25 Gaia data release?
More than a billion, but identifying which of the Gaia stars they orbit is left as an exercise to the reader ;)

More seriously, a summary of Gaia exoplanet potential http://sci.esa.int/gaia/58784-exoplanets/

According to https://www.cosmos.esa.int/web/gaia/release exoplanets are expected in DR5.

Since Gaia will mostly detect exoplanets by astrometry, it requires long time baselines.
Title: Re: ESA - Gaia updates
Post by: bolun on 04/07/2018 07:41 am
WAITING FOR GAIA'S SECOND DATA RELEASE

Based on 22 months of observations, the second release of Gaia's data contains the position on the sky and brightness of 1 692 919 135 stars, as well as measurements of the parallax and proper motion of 1 331 909 727 stars.

It also includes a wide range of additional information: the colours of 1.38 billion stars; the radial velocities of 7 224 631 stars; information about 550 737 variable sources; an estimate of the surface temperature for 161 497 595 stars, of the extinction – a measure of the amount of dust along the line of sight – for 87 733 672 stars, and of the radius and luminosity of 76 956 778 stars.

Closer to home, the new data set also contains the position of 14 099 Solar System objects – mostly asteroids – based on more than 1.5 million observations.

The second data release of Gaia is scheduled for publication on 25 April 2018.

- Related article: How many stars to expect in Gaia's second data release (http://sci.esa.int/gaia/60146-how-many-stars-to-expect-in-gaia-s-second-data-release/)

http://sci.esa.int/gaia/60147-waiting-for-gaia-s-second-data-release/

Image credit: ESA, CC BY-SA 3.0 IGO
Title: Re: ESA - Gaia updates
Post by: Star One on 04/07/2018 10:30 am
Saw this mentioned elsewhere will the standard errors be in the catalogue?
Title: Re: ESA - Gaia updates
Post by: as58 on 04/07/2018 11:13 am
Saw this mentioned elsewhere will the standard errors be in the catalogue?

I'm not sure what exactly you mean, but detailed information about the upcoming data release can be found at https://www.cosmos.esa.int/web/gaia/dr2
Title: Re: ESA - Gaia updates
Post by: Star One on 04/07/2018 02:17 pm
Saw this mentioned elsewhere will the standard errors be in the catalogue?

I'm not sure what exactly you mean, but detailed information about the upcoming data release can be found at https://www.cosmos.esa.int/web/gaia/dr2

I just saw the question asked on a astronomy forum but no one gave an answer.
Title: Re: ESA - Gaia updates
Post by: Hungry4info3 on 04/07/2018 03:40 pm
From the link as58 gave you,
Quote
Parallax uncertainties are in the range of up to 0.04 milliarcsecond for sources at G < 15, around 0.1 mas for sources with G=17 and at the faint end, the uncertainty is of the order of 0.7 mas at G = 20. The corresponding uncertainties in the respective proper motion components are up to 0.06 mas yr-1 (for G < 15 mag), 0.2 mas yr-1 (for G = 17 mag) and 1.2 mas yr-1 (for G = 20 mag).
Title: Re: ESA - Gaia updates
Post by: Star One on 04/07/2018 05:10 pm
From the link as58 gave you,
Quote
Parallax uncertainties are in the range of up to 0.04 milliarcsecond for sources at G < 15, around 0.1 mas for sources with G=17 and at the faint end, the uncertainty is of the order of 0.7 mas at G = 20. The corresponding uncertainties in the respective proper motion components are up to 0.06 mas yr-1 (for G < 15 mag), 0.2 mas yr-1 (for G = 17 mag) and 1.2 mas yr-1 (for G = 20 mag).

Thank you.
Title: Re: ESA - Gaia updates
Post by: Star One on 04/21/2018 09:33 am
Waiting for Gaia

https://youtu.be/FPQ4HZITk5A
Title: Re: ESA - Gaia updates
Post by: Star One on 04/22/2018 08:15 am
Media Kit for Gaia DR 2

http://sci.esa.int/gaia/60174-media-kit-for-gaia-data-release-2/
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/25/2018 08:16 am
Reminder the second data release is scheduled to be aired live less than an hour from now (11 am CEST): esa.int/live
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/25/2018 09:43 am
Quote
Gaia’s all-sky view of our Milky Way Galaxy and neighbouring galaxies, based on measurements of nearly 1.7 billion stars. The map shows the total brightness and colour of stars observed by the ESA satellite in each portion of the sky between July 2014 and May 2016.
Brighter regions indicate denser concentrations of especially bright stars, while darker regions correspond to patches of the sky where fewer bright stars are observed. The colour representation is obtained by combining the total amount of light with the amount of blue and red light recorded by Gaia in each patch of the sky.
The bright horizontal structure that dominates the image is the Galactic plane, the flattened disc that hosts most of the stars in our home Galaxy. In the middle of the image, the Galactic centre appears vivid and teeming with stars.
Darker regions across the Galactic plane correspond to foreground clouds of interstellar gas and dust, which absorb the light of stars located further away, behind the clouds. Many of these conceal stellar nurseries where new generations of stars are being born.
Sprinkled across the image are also many globular and open clusters – groupings of stars held together by their mutual gravity, as well as entire galaxies beyond our own.
The two bright objects in the lower right of the image are the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way.
In small areas of the image where no colour information was available – to the lower left of the Galactic centre, to the upper left of the Small Magellanic Cloud, and in the top portion of the map – an equivalent greyscale value was assigned.
The second Gaia data release was made public on 25 April 2018 and includes the position and brightness of almost 1.7 billion stars, and the parallax, proper motion and colour of more than 1.3 billion stars. It also includes the radial velocity of more than seven million stars, the surface temperature of more than 100 million stars, and the amount of dust intervening between us and of 87 million stars. There are also more than 500 000 variable sources, and the position of 14 099 known Solar System objects – most of them asteroids – included in the release.
Acknowledgement: Gaia Data Processing and Analysis Consortium (DPAC); A. Moitinho / A. F. Silva / M. Barros / C. Barata, University of Lisbon, Portugal; H. Savietto, Fork Research, Portugal.
http://www.esa.int/spaceinimages/Images/2018/04/Gaia_s_sky_in_colour2 (http://www.esa.int/spaceinimages/Images/2018/04/Gaia_s_sky_in_colour2)
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/25/2018 10:07 am
Quote from: @ESAGaia
We're online with #GaiaDR2. You are all so very excited to get the data we are bit overloaded! 256 users in the first two minutes alone!

All topics:

https://www.cosmos.esa.int/web/gaia/iow_20180425
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 10:10 am
It's going to take a while to digest, but the visualisations are stunning (and some are quite unexpected)!
Title: Re: ESA - Gaia updates
Post by: bolun on 04/25/2018 10:14 am
Gaia Archive: http://gea.esac.esa.int/archive/
Title: Re: ESA - Gaia updates
Post by: bolun on 04/25/2018 10:17 am
Gaia creates richest star map of our Galaxy - and beyond (article)

25 April 2018

https://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_creates_richest_star_map_of_our_Galaxy_and_beyond
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 11:13 am
Here's the first tranche of papers, 11 of which are open access:

https://www.aanda.org/component/toc/?task=topic&id=922 (https://www.aanda.org/component/toc/?task=topic&id=922)
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/25/2018 12:52 pm
I had never seen such a map before (I suppose some previous version of it, even with a rough spatial binning, existed?) but I like it :)
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 12:57 pm
I had never seen such a map before (I suppose some previous version of it, even with a rough spatial binning, existed?) but I like it :)

I've not seen anything like that before either, and it was the thing that most surprised me: spatial galactic radial velocity differences.
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/25/2018 01:18 pm
I had never seen such a map before (I suppose some previous version of it, even with a rough spatial binning, existed?) but I like it :)

I've not seen anything like that before either, and it was the thing that most surprised me: spatial galactic radial velocity differences.

It makes sense these "counter-currents" are located as shown, since it has been known for a long time the Sun lies in the periphery of a galactic arm (in fact, one of the first science-related trivia I remember from when I was a child was this one nugget!). However, our location almost precisely at the boundary between such large volumes of opposite movement -2 kpc wide no less, 6500 light-years!- really drives home the relative uniqueness of our neighborhood. I wonder what effects, if any, this "borderland" condition has on the dynamics and compositions of our local neighborhood or Solar System.

Relative because there's probably more than half a Mpc's worth of such "unique" areas in the combined Milky Way's arm boundaries :)
Title: Re: ESA - Gaia updates
Post by: Star One on 04/25/2018 03:17 pm
How many hypervelocity stars are there in the catalogue?
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 03:30 pm
It makes sense these "counter-currents" are located as shown, since it has been known for a long time the Sun lies in the periphery of a galactic arm (in fact, one of the first science-related trivia I remember from when I was a child was this one nugget!).

I'm not at all sure this is related to the spiral structure. The colours are Vr (i.e. radial velocity relative to the galactic centre).  As all the stars are orbiting the centre in roughly circular orbits, this spatial distributiuon is surprising - at least to me, but I must admit to not knowing much about galaxies ...

--- Tony

Title: Re: ESA - Gaia updates
Post by: Star One on 04/25/2018 03:41 pm
New data release sparks astronomy revolution

Quote
Astronomy professor Helmi lead author of one of six papers describing the quality of the Gaia data

Quote
The data shows, for example, two satellite galaxies with a very similar trajectory. This suggests they share a common origin. The trajectories of satellite galaxies are also governed by how the mass of the Milky Way is distributed, especially in the halo. ‘We can now estimate the mass distribution in the halo of the Milky Way more accurately, and this is where dark matter dominates and dictates the motion of stars, globular clusters and satellite galaxies. This means we should be able to probe much more directly the nature of dark matter and test whether the law of Gravity needs modification.

https://www.rug.nl/news/2018/04/new-data-release-sparks-astronomy-revolution
Title: Re: ESA - Gaia updates
Post by: as58 on 04/25/2018 03:47 pm
It makes sense these "counter-currents" are located as shown, since it has been known for a long time the Sun lies in the periphery of a galactic arm (in fact, one of the first science-related trivia I remember from when I was a child was this one nugget!).

I'm not at all sure this is related to the spiral structure. The colours are Vr (i.e. radial velocity relative to the galactic centre).  As all the stars are orbiting the centre in roughly circular orbits, this spatial distributiuon is surprising - at least to me, but I must admit to not knowing much about galaxies ...

--- Tony

Where's the map from? I can't find it on the ESA site and I'd like to see some explanation about it.
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 03:50 pm
Where's the map from? I can't find it on the ESA site and I'd like to see some explanation about it.

It was shown in the press conference, but I can't find it on the site [ and they talked about it as galactic radial velocity, which matches the VbarR on the plot ].  The lady presenting likened it to ripples in a pond.

--- Tony
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/25/2018 04:18 pm
This one is also very nice, clearly showing the rotation of the galaxy.

--- Tony
Title: ESA - Gaia updates
Post by: Star One on 04/25/2018 05:06 pm
Gaia second data release

https://www.youtube.com/watch?v=VINs-JcNmKs
Title: Re: ESA - Gaia updates
Post by: eeergo on 04/26/2018 12:52 am
It makes sense these "counter-currents" are located as shown, since it has been known for a long time the Sun lies in the periphery of a galactic arm (in fact, one of the first science-related trivia I remember from when I was a child was this one nugget!).

I'm not at all sure this is related to the spiral structure. The colours are Vr (i.e. radial velocity relative to the galactic centre).  As all the stars are orbiting the centre in roughly circular orbits, this spatial distributiuon is surprising - at least to me, but I must admit to not knowing much about galaxies ...

--- Tony

Where's the map from? I can't find it on the ESA site and I'd like to see some explanation about it.

https://twitter.com/rdrimmel/status/989083026213785601

My intuitive and not at all specialized understanding leads me to think the denser, star-rich arm regions are moving in roughly circular orbits with a small component that draws them inwards towards the center, while the more sparsely populated areas outside the arms get pushed outwards. No idea what the implications are for this, or if it was expected based on prior knowledge though.
Title: Re: ESA - Gaia updates
Post by: ugordan on 04/26/2018 07:08 am
This is pretty neat, Kepler original field of view with Gaia-supplied proper motions extrapolated 500 000 years into the past and into the future:

https://twitter.com/meg_bedell/status/989322975261396992

Video attached
Title: Re: ESA - Gaia updates
Post by: jebbo on 04/26/2018 08:01 am
The papers are now available on Arxiv.  List here (https://www.cosmos.esa.int/web/gaia/dr2-papers)
Title: Re: ESA - Gaia updates
Post by: Alpha_Centauri on 04/26/2018 11:11 am
It makes sense these "counter-currents" are located as shown, since it has been known for a long time the Sun lies in the periphery of a galactic arm (in fact, one of the first science-related trivia I remember from when I was a child was this one nugget!).

I'm not at all sure this is related to the spiral structure. The colours are Vr (i.e. radial velocity relative to the galactic centre).  As all the stars are orbiting the centre in roughly circular orbits, this spatial distributiuon is surprising - at least to me, but I must admit to not knowing much about galaxies ...

--- Tony

Where's the map from? I can't find it on the ESA site and I'd like to see some explanation about it.
It's in the paper "Gaia Data Release 2: Mapping the Milky Way disc kinematics"

https://arxiv.org/pdf/1804.09380.pdf
Title: Re: ESA - Gaia updates
Post by: Star One on 04/26/2018 07:54 pm
Article summing up some of the groups working on the Gaia data.

https://blogs.scientificamerican.com/observations/the-milky-way-revealed-as-never-before/
Title: Re: ESA - Gaia updates
Post by: Phil Stooke on 04/26/2018 08:25 pm
The elliptical map (Mollweide projection of the sky) is in galactic coordinates.  The plane of the galaxy, if you like, the galactic equator, is the line running horizontally through the middle of the ellipse.  The center of the galaxy is in the middle of the map.  If you are looking towards the middle of the galaxy, the stars orbiting closer to the center are moving away from us to the left and towards us to the right of center, producing the red and blue shifts.  If you turn around and face outwards, away from the galactic center, you are now looking at the hemisphere of the sky which, in this projection, is split and appended to the left and right ends of the elliptical whole-sky map.  We are moving faster than the more distant stars, so the ones to our left (but on the right half of the map) are falling behind, moving away from us, so are red-shifted.  The stars to our right (looking outwards), on the left half of the map, are the ones we are 'overtaking', so they are getting closer and are blue-shifted. 

If the division of the sky like this seems puzzling, look at a Mollweide projection of Earth - the middle region is one hemisphere, the crescent-shaped appendages on each side are the opposite hemisphere.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 04/30/2018 06:10 pm
UK's contribution to Gaia:

https://stfc.ukri.org/news/3-d-map-of-the-milky-way/

So the UK Space Agency is funding Ł4 million a year in processing. Considering that the project is computationally very intensive and getting a result is an issue of getting crunching power and not just good software, this is good news. Now, if only the other countries that are members of Gaia DPAC would put out this sort of press release.
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/01/2018 06:55 am
Quite a crop of Gaia papers today:
Gaia DR2 Distances and Peculiar Velocities for Galactic Black Hole Transients (https://arxiv.org/abs/1804.11349)
Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motions (https://arxiv.org/abs/1804.11348)
One large blob and many streams frosting the nearby stellar halo in Gaia DR2 (https://arxiv.org/abs/1804.11347)
Ghostly Tributaries to the Milky Way: Charting the Halo's Stellar Streams with the Gaia DR2 catalogue (https://arxiv.org/abs/1804.11339)
Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae (https://arxiv.org/abs/1804.11163)
Evidence for unresolved exoplanet-hosting binaries in Gaia DR2 (https://arxiv.org/abs/1804.11082)
Title: Re: ESA - Gaia updates
Post by: AlexA on 05/01/2018 10:17 am
Interesting paper:

https://arxiv.org/abs/1804.08351 (https://arxiv.org/abs/1804.08351)

Quote
SETI with Gaia: The observational signatures of nearly complete Dyson spheres

Erik Zackrisson, Andreas J. Korn, Ansgar Wehrhahn, Johannes Reiter

(Submitted on 23 Apr 2018)

A star enshrouded in a Dyson sphere with high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson-sphere searches that are complementary to searches based on waste-heat signatures at infrared wavelengths. A limited search of this type is also possible at the current time, by combining Gaia parallax distances with spectrophotometric distances from ground-based surveys. Here, we discuss the merits and shortcomings of this technique and carry out a limited search for Dyson-sphere candidates in the sample of stars common to Gaia Data Release 1 and RAVE Data Release 5. We find that a small fraction of stars indeed display distance discrepancies of the type expected for nearly complete Dyson spheres. To shed light on the properties of objects in this outlier population, we present follow-up high-resolution spectroscopy for one of these stars, the late F-type dwarf TYC 6111-1162-1. The spectrophotometric distance of this object is about twice that derived from its Gaia parallax, and there is no detectable infrared excess. While our analysis largely confirms the stellar parameters and the spectrophotometric distance inferred by RAVE, a plausible explanation for the discrepant distance estimates of this object is that the astrometric solution has been compromised by an unseen binary companion, possibly a rather massive white dwarf (≈1 M ⊙  ). This scenario can be further tested through upcoming Gaia data releases.
Title: Re: ESA - Gaia updates
Post by: Star One on 05/01/2018 04:53 pm
Interesting paper:

https://arxiv.org/abs/1804.08351 (https://arxiv.org/abs/1804.08351)

Quote
SETI with Gaia: The observational signatures of nearly complete Dyson spheres

Erik Zackrisson, Andreas J. Korn, Ansgar Wehrhahn, Johannes Reiter

(Submitted on 23 Apr 2018)

A star enshrouded in a Dyson sphere with high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson-sphere searches that are complementary to searches based on waste-heat signatures at infrared wavelengths. A limited search of this type is also possible at the current time, by combining Gaia parallax distances with spectrophotometric distances from ground-based surveys. Here, we discuss the merits and shortcomings of this technique and carry out a limited search for Dyson-sphere candidates in the sample of stars common to Gaia Data Release 1 and RAVE Data Release 5. We find that a small fraction of stars indeed display distance discrepancies of the type expected for nearly complete Dyson spheres. To shed light on the properties of objects in this outlier population, we present follow-up high-resolution spectroscopy for one of these stars, the late F-type dwarf TYC 6111-1162-1. The spectrophotometric distance of this object is about twice that derived from its Gaia parallax, and there is no detectable infrared excess. While our analysis largely confirms the stellar parameters and the spectrophotometric distance inferred by RAVE, a plausible explanation for the discrepant distance estimates of this object is that the astrometric solution has been compromised by an unseen binary companion, possibly a rather massive white dwarf (≈1 M ⊙  ). This scenario can be further tested through upcoming Gaia data releases.

https://forum.nasaspaceflight.com/index.php?PHPSESSID=aco9gun18v8geg40198mkbtb86;topic=43914.msg1814143#msg1814143

I didn’t post it in here as I know some forum members are hyper allergic to any mention of SETI.
Title: Re: ESA - Gaia updates
Post by: Star One on 05/03/2018 07:53 pm
Evidence for Unresolved Exoplanet-hosting Binaries in Gaia DR2

Quote
This note describes an effort to detect additional stellar sources in known transiting exoplanet (TEP) systems, which are unresolved or barely resolved in the Gaia Data Release 2 (DR2) catalog (Gaia Collaboration et al. 2016, 2018). The presence of multiple unresolved stars in photometric and spectroscopic observations of a transiting planetary system biases measurements of the planet's radius, mass, and atmospheric conditions (e.g., Buchhave et al. 2011; Evans et al. 2016; Southworth & Evans 2016). In addition to the effect on individual planetary systems, the presence of unresolved stars across the sample of known exoplanets biases our overall understanding of planetary systems, due to the systematic underestimation of both masses and radii (Ciardi et al. 2015).

http://iopscience.iop.org/article/10.3847/2515-5172/aac173/meta
Title: Re: ESA - Gaia updates
Post by: Star One on 05/07/2018 07:45 pm
Gaia Reveals Evidence for Merged White Dwarfs

We use Gaia Data Release 2 to identify 13,928 white dwarfs within 100 pc of the Sun. The exquisite astrometry and photometry from Gaia reveals for the first time a bifurcation in the observed white dwarf sequence in both Gaia and the Sloan Digital Sky Survey passbands. The latter is easily explained by a helium atmosphere (DB) white dwarf fraction of 36%. However, the bifurcation in the Gaia passbands cannot be explained by DB white dwarfs. We simulate theoretical color-magnitude diagrams for single and binary white dwarfs using a population synthesis approach and demonstrate that the only way to explain the bifurcation in the Gaia data is through a significant contribution from single white dwarfs that formed through mergers. This is the first direct detection of such a population in the solar neighborhood.

https://arxiv.org/abs/1805.01227
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 05/10/2018 09:09 pm
Spain's contribution to Gaia DPAC:

https://www.res.es/en/news/gaia-creates-richest-star-map-our-galaxy-participation-two-res-nodes

There is also a large number of discoveries coming out of GaiaDR2. A twitter search for the hashtag #GaiaDR2 reveals quite a number of papers out. New stellar streams, new open star clusters, error margins in the DR2 parallaxes and other stuff. The typical method seems to be run a script on DR2, pull out interesting stars, cross check with other catalogs or at best a couple of days of observations and then publish your findings.
Title: Re: ESA - Gaia updates
Post by: philw1776 on 05/15/2018 04:45 pm
Generic public article on early Gaia papers & results...
https://www.sciencenews.org/article/gaia-delivers-trove-data-revealing-secrets-milky-way

Couple of favorites interesting to me...

Improved radii for Kepler stars & exoplanets
https://arxiv.org/abs/1805.00231


Better Cepheid distances and problems with cosmic expansion rates
https://arxiv.org/abs/1804.10655

"Including the DR2 parallaxes with all prior distance ladder data raises the current tension between the late and early Universe route to the Hubble constant to 3.8 sigma (99.99 %)."
Title: Re: ESA - Gaia updates
Post by: Star One on 05/18/2018 03:42 pm
ESA Euronews: Gaia’s revolution in astronomy

https://youtu.be/doSoTYRPVtE
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 06/11/2018 06:55 pm
The amount of research coming out of DR2 is just amazing. Last week there was a Gaia sprint in New York, and I found amazing just what they are trying to pull out of the data. The pitch slides are here:

https://docs.google.com/presentation/d/19_Un3VQrB9d7Ftczf9yNxoJkW6BDe-EtDbrjSR6mMHY/edit#slide=id.p

On Gaia news, as I read them on twitter, they are trying to pull out binaries misclassified as single stars out of the spectra based on their position on the H-R diagram. Also it seems that in DR2 galaxies were misclassified as variable stars because of the way Gaia scans: Galaxies are, for the most part, not spherical. Since Gaia sees the star in different angles, it passes a different cross section of the galaxy with a different brightness leading to the misclassification. As someone who measured classification error in land cover datasets for the first part of his dissertation, I feel empathy for the researchers.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 06/23/2018 07:41 am
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars. This seems to correspond to where dwarfs transition to partial to fully convective. The Gaia team members have weighed in on twitter and do not believe that this is a systematic error, rather a real effect.

arXiv paper: https://arxiv.org/abs/1806.07792

A Gap in the Lower Main Sequence Revealed by Gaia Data Release 2

Synopsis: We present the discovery of a gap near MG≈10 in the main sequence on the Hertzsprung-Russell Diagram (HRD) based on measurements presented in Gaia Data Release 2 (DR2). Using an observational form of the HRD with MG representing luminosity and GBP−GRP representing temperature, the gap presents a diagonal feature that dips toward lower luminosities at redder colors. The gap is seen in samples extracted from DR2 with various distances, and is not unique to the {\it Gaia} photometry --- it also appears when using near-IR photometry (J−Ks vs MKs). The gap is very narrow (∼0.05 mag) and is near the luminosity-temperature regime where M dwarf stars transition from partially to fully convective, i.e., near spectral type M3.0V. This gap provides a new feature in the H-R Diagram that hints at an underlying astrophysical cause and we propose that it is linked to the onset of full convection in M dwarfs.
Title: Re: ESA - Gaia updates
Post by: CuddlyRocket on 06/24/2018 01:19 am
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars.

So, who's this gap going to be named after? :)
Title: Re: ESA - Gaia updates
Post by: Ben the Space Brit on 06/24/2018 07:35 am
That's interesting. Might there be a 'threshold energy' required to jump into full convection that's lower than the linear energy increase just below M3?
Title: Re: ESA - Gaia updates
Post by: jebbo on 06/25/2018 07:54 am
I think you have that the wrong way around: dwarfs *later* (smaller) than M3V are fully convective.

So it seems to imply an energy threshold for developing an outer radiative zone.

--- Tony
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 06/25/2018 09:36 pm
Another new Gaia discovery that popped up on twitter today: there is a gap in the HR main sequence stars.

So, who's this gap going to be named after? :)

How about Van Ness gap? In downtown Fresno, the next street over from Fulton Street is Van Ness Street. And sure, Fulton is a person and Fresno is pretty obscure as a place, but that doesn't mean we should have fun :)

On a more serious note there was a Gaia workshop in Heidelberg last week, not to be confused with the one in Barcelona taking place this week, and the presentations are up at:
http://gaia.ari.uni-heidelberg.de/gaia-workshop-2018/programme.html

Most interestingly in the very first presentation by Biermann there is the last slide (attached)


Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 07/03/2018 07:10 am
Speaking of gaps, this paper, based on Gaia and Kepler claims that there are gaps at 2 Earth radii (rocky planets), 4 Earth radii (water worlds) and 10 Earth radii (transition worlds to gas giants above 10)

https://arxiv.org/abs/1806.11234

Abstract:
<quote> Applying the survival function analysis to the planet radius distribution of the Kepler confirmed/candidate planets, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplanets from large exoplanets above. When combined with the recently-discovered radius gap at 2 Earth radii, it supports the treatment of planets 2-4 Earth radii as a separate group, likely water worlds. For planets around solar-type FGK main-sequence stars, we argue that 2 Earth radii is the separation between water-poor and water-rich planets, and 4 Earth radii is the separation between gas-poor and gas-rich planets. We confirm that the slope of survival function in between 4 and 10 Earth radii to be shallower compared to either ends, indicating a relative paucity of planets in between 4-10 Earth radii, namely, the sub-Saturnian desert there. We name them transitional planets, as they form a bridge between the gas-poor small planets and gas giants. Accordingly, we propose the following classification scheme: (<2 Earth radii) rocky planets, (2-4 Earth radii) water worlds, (4-10 Earth radii) transitional planets, and (>10 Earth radii) gas giants.  </quote>
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 07/05/2018 07:40 am
Discovery of the day: the Milky Way collided early in its history with a galaxy dubbed "the Gaia Sausage" and this is visible in radial velocities:

https://www.simonsfoundation.org/2018/07/04/gaia-sausage-galaxy/

Now usually when scientists want to say something more elegantly than their mother tongue and obfuscate a colloquialism, they use ancient Greek. Ancient Greek for sausage is "άλλας", or allas to spell it in the Latin alphabet. Could it be that in the future this progenitor galaxy will be known as the Allas Galaxy rather than the Gaia sausage?
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 08/18/2018 07:16 am
Gaia is the give that keeps on giving, as it has been called, and is the star in a series of astronomy conferences. Many of those conferences I did not know that they existed, but then again I am not an astronomer. Now CoolStars20 has put up both slides and lectures up, and from that here is a Gaia mission overview:

https://coolstars20.github.io/talkpdf/Thevenin.pdf
Title: Re: ESA - Gaia updates
Post by: bolun on 08/21/2018 03:50 pm
Infant exoplanet weighed by Hipparcos and Gaia

https://www.esa.int/Our_Activities/Space_Science/Gaia/Infant_exoplanet_weighed_by_Hipparcos_and_Gaia
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 09/13/2018 08:47 pm
Impressions from the IAU general assembly

https://www.cosmos.esa.int/web/gaia/iow_20180911

Gaia had an entire session dedicated to it, and on the ESA booth they had demonstrations on how to use its data and a VR exhibit using GaiaSky that allowed to experience the Gaia mapped part of the galaxy in 3-D, or so I read. The news release contains links to the slides from 5 presentations. Gaia DR3 is now expected early 2021 rather than late 2020 previously. They are characterizing errors and biases better, setting up new pipelines for new products (such as the 100,000+ solar system objects) and tweaking their code. From what I read, if it was just an issue of doing DR2 with more data, DR3 would have been released already
Title: Re: ESA - Gaia updates
Post by: bolun on 09/20/2018 12:53 pm
Gaia hints at our Galaxy's turbulent life

19 September 2018

ESA's star mapping mission, Gaia, has shown our Milky Way galaxy is still enduring the effects of a near collision that set millions of stars moving like ripples on a pond.

The close encounter likely took place sometime in the past 300–900 million years. It was discovered because of the pattern of movement it has given to stars in the Milky Way disc – one of the major components of our Galaxy.

The pattern was revealed because Gaia not only accurately measures the positions of more than a billion stars but also precisely measures their velocities on the plane of the sky. For a subset of a few million stars, Gaia provided an estimate of the full three-dimensional velocities, allowing a study of stellar motion using the combination of position and velocity, which is known as 'phase space'.

In phase space, the stellar motions revealed an interesting and totally unexpected pattern when the star's positions were plotted against their velocities. Teresa Antoja from Universitat de Barcelona, Spain, who led the research couldn't quite believe her eyes when she first saw it on her computer screen.

One shape in particular caught her attention. It was a snail shell-like pattern in the graph that plotted the stars' altitude above or below the plane of the Galaxy against their velocity in the same direction. It had never been seen before.

http://sci.esa.int/gaia/60663-gaia-hints-at-our-galaxys-turbulent-life/

Image credit: ESA, CC BY-SA 3.0 IGO
Title: Re: ESA - Gaia updates
Post by: bolun on 09/25/2018 06:42 pm
http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_finds_candidates_for_interstellar_Oumuamua_s_home

Gaia finds candidates for interstellar 'Oumuamua's home

Quote
Using data from ESA’s Gaia stellar surveyor, astronomers have identified four stars that are possible places of origin of ‘Oumuamua, an interstellar object spotted during a brief visit to our Solar System in 2017.

Quote
While future observations of these four stars might shed new light on their properties and potential to be the home system of ‘Oumuamua, the astronomers are also looking forward to future releases of Gaia data. At least two are planned in the 2020s, which will include a much larger sample of radial velocities, enabling them to reconstruct and investigate the trajectories of many more stars.


Title: Re: ESA - Gaia updates
Post by: bolun on 10/02/2018 03:22 pm
Gaia spots stars flying between galaxies

https://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_spots_stars_flying_between_galaxies
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/06/2018 06:50 am
Gaia - The stereoscopic survey of the galaxy

https://www.youtube.com/watch?v=BdOrqooSS64

This is a lecture at the colloquium of the Harvard - Smithsonian Center for Astrophysics. It is thus at a higher level than press events intended for the general public but not as complicated as a conference lecture. This is not a lecture about what they found in the catalog. It is a lecture on the mission from its inception in 1993 to today. It is very interesting when talking about all the science that Gaia is doing that its very high accuracy allows: For example they are detecting the relativistic bending of light by Jupiter at the 2000σ level, and in 2019 in honor of the century since Eddington measured the bending of the stars during an eclipse as Einstein predicted they intend to measure the effects from the rotation of Jupiter. I really liked this lecture.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/26/2018 05:42 am
A re-classification of Cepheids in the Gaia Data Release 2
https://arxiv.org/abs/1810.10486
Quote
lassical Cepheids are the most important primary indicators for the extragalactic distance scale. Establishing the precise zero points of their Period-Luminosity and Period-Wesenheit (PL/PW) relations has profound consequences on the estimate of H0. Type II Cepheids are also important distance indicator and tracers of old stellar populations. The recent Data Release 2 (DR2) of the {\it Gaia} Spacecraft includes photometry and parallaxes for thousands of classical and type II cepheids. We aim at reviewing the classification of {\it Gaia} DR2 Cepheids and to derive precise PL/PW for Magellanic Cloud (MCs) and Galactic Cepheids.
Information from the literature and the {\it Gaia} astrometry and photometry are adopted to assign DR2 Galactic Cepheids to the classes: Classical, Anomalous and Type II Cepheids. We re-classify the DR2 Galactic Cepheids and derive new precise PL/PW relations in the {\it Gaia} passbands for the MCs and Milky Way Cepheids. According to our analysis, the zero point of the {\it Gaia} DR2 parallaxes as estimated from Classical and Type II Cepheids seems to be likely underestimated by ∼0.07 mas, about 50\% more than what estimated in the recent literature for Classical Cepheids. The next {\it Gaia} data releases are expected to fix this zero point offset to eventually allow a determination of H0 to less than 1\%.

They will use the findings of the paper to improve the Cepheids pipeline for DR3 and DR4
Title: Re: ESA - Gaia updates
Post by: Star One on 11/01/2018 09:01 pm
GALACTIC GHOSTS: GAIA UNCOVERS MAJOR EVENT IN THE FORMATION OF THE MILKY WAY (http://sci.esa.int/gaia/60892-galactic-ghosts-gaia-uncovers-major-event-in-the-formation-of-the-milky-way/)

Quote
ESA's Gaia mission has made a major breakthrough in unravelling the formation history of the Milky Way. Instead of forming alone, our Galaxy merged with another large galaxy early in its life, around 10 billion years ago. The evidence is littered across the sky all around us, but it has taken Gaia and its extraordinary precision to show us what has been hiding in plain sight all along.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 11/01/2018 09:19 pm
GALACTIC GHOSTS: GAIA UNCOVERS MAJOR EVENT IN THE FORMATION OF THE MILKY WAY (http://sci.esa.int/gaia/60892-galactic-ghosts-gaia-uncovers-major-event-in-the-formation-of-the-milky-way/)

Quote
ESA's Gaia mission has made a major breakthrough in unravelling the formation history of the Milky Way. Instead of forming alone, our Galaxy merged with another large galaxy early in its life, around 10 billion years ago. The evidence is littered across the sky all around us, but it has taken Gaia and its extraordinary precision to show us what has been hiding in plain sight all along.

I assume this must be the sausage, mentioned earlier. I much prefer Gaia-Enceladus
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 12/07/2018 11:21 pm
It seems that we have missed here the discovery of the dwarf galaxy Antlia 2, on the other side of the Milky Way and about the size of the Large Magellanic Cloud. Below is an interesting lecture on using Gaia data to search for Dark Matter. Interestingly the lecturer goes oldskool, boards rather than slides. He has a slide (or two) in the end that is not visible:

https://www.youtube.com/watch?v=SeIyH-S3zik
Title: Re: ESA - Gaia updates
Post by: Star One on 12/08/2018 09:40 am
Here’s the discovery paper for Antila 2.

The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (https://arxiv.org/abs/1811.04082)

Quote
We report the discovery of a Milky-Way satellite in the constellation of Antlia. The Antlia 2 dwarf galaxy is located behind the Galactic disc at a latitude of b∼11∘ and spans 1.26 degrees, which corresponds to ∼2.9 kpc at its distance of 130 kpc. While similar in extent to the Large Magellanic Cloud, Antlia~2 is orders of magnitude fainter with MV=−8.5 mag, making it by far the lowest surface brightness system known (at 32.3 mag/arcsec2), ∼100 times more diffuse than the so-called ultra diffuse galaxies. The satellite was identified using a combination of astrometry, photometry and variability data from Gaia Data Release 2, and its nature confirmed with deep archival DECam imaging, which revealed a conspicuous BHB signal. We have also obtained follow-up spectroscopy using AAOmega on the AAT to measure the dwarf's systemic velocity, 290.9±0.5km/s, its velocity dispersion, 5.7±1.1 km/s, and mean metallicity, [Fe/H]=−1.4. From these properties we conclude that Antlia~2 inhabits one of the least dense Dark Matter (DM) halos probed to date. Dynamical modelling and tidal-disruption simulations suggest that a combination of a cored DM profile and strong tidal stripping may explain the observed properties of this satellite. The origin of this core may be consistent with aggressive feedback, or may even require alternatives to cold dark matter (such as ultra-light bosons).
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 12/21/2018 05:22 pm
This is very silly: now there is Jingle Bells made from sonification of the Gaia light curves:

https://www.cosmos.esa.int/web/gaia/iow_20181221

If you look at the bottom, they even put custom lyrics
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/14/2019 08:49 pm
Gaia reveals how Sun-like stars turn solid after their demise

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_reveals_how_Sun-like_stars_turn_solid_after_their_demise
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/17/2019 06:52 pm
From Nature: an overview of the discoveries on the structure of the Milky Way by Gaia

https://www.nature.com/articles/d41586-019-00123-y
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/29/2019 08:28 pm
New Star Maps Shed Light on Milky Way’s Convulsive History

https://www.scientificamerican.com/article/new-star-maps-shed-light-on-milky-ways-convulsive-history/

Nice summary of some of what has been found so far in DR2. It is lacking in some of the newer stuff that has appeared in arXiv such as the 8 new star streams in the galactic center
Title: Re: ESA - Gaia updates
Post by: bolun on 02/12/2019 03:02 pm
Gaia clocks new speeds for Milky Way-Andromeda collision

07 February 2019

ESA's Gaia satellite has looked beyond our Galaxy and explored two nearby galaxies to reveal the stellar motions within them and how they will one day interact and collide with the Milky Way – with surprising results.

Our Milky Way belongs to a large gathering of galaxies known as the Local Group and, along with the Andromeda and Triangulum galaxies – also referred to as M31 and M33, respectively – makes up the majority of the group's mass.

Astronomers have long suspected that Andromeda will one day collide with the Milky Way, completely reshaping our cosmic neighbourhood. However, the three-dimensional movements of the Local Group galaxies remained unclear, painting an uncertain picture of the Milky Way's future.

http://sci.esa.int/gaia/61116-gaia-clocks-new-speeds-for-milky-way-andromeda-collision/

Image credit: Orbits: E. Patel, G. Besla (University of Arizona), R. van der Marel (STScI); Images: ESA (Milky Way); ESA/Gaia/DPAC (M31, M33)
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 02/15/2019 06:17 pm
Gaia newsletter #5 is out:

https://www.cosmos.esa.int/web/gaia/newsletter/contents

Apparently on January 29 2019 it was announced that DR3 is to be split in two: the Early DR 3 will include what was in DR2 but over 34 months of data and fewer systematic errors, and will come out Q3 2020. Full DR3, which will also copy what is in EDR3, will include new stuff and is set for later 2021.

Quote
The early release, Gaia EDR3, contains astrometry and (integrated) photometry i.e. positions, parallaxes, proper motions, G-band fluxes as well as integrated red- (RP) and blue-band (BP) fluxes, all based on 34 months of data resulting in better accuracy with respect to Gaia DR2. First results for a predefined list of quasars and extended objects may also be included already in the early release. Gaia EDR3 will take place in Q3 of 2020.

Gaia DR3, which is anticipated to take place during the second half of 2021, will supersede Gaia EDR3. This means that the source list and any data published in Gaia EDR3 will not change, but is simply copied to Gaia DR3. Therefore Gaia DR3 is based on the same 34 months of mission data as for Gaia EDR3. The additional products include:
- radial velocities (significantly more due to fainter magnitude limit),
- BP/RP/RVS spectra (new products),
- Solar system data (significantly more sources included),
- variability information (significantly more objects due to longer time interval),
- results for non-single stars (new products), and
- astrophysical parameters (based on spectra).
The final inclusion of the products into Gaia DR3, as well as Gaia EDR3, is subject to successful validation.
Title: Re: ESA - Gaia updates
Post by: Star One on 04/23/2019 09:06 pm
Omega Centauri’s lost stars (http://www.cfht.hawaii.edu/en/news/OmegaCen/)

Quote
A team of researchers from the Strasbourg Astronomical Observatory, Bologna Observatory and the University of Stockholm has identified a stream of stars that was torn off the globular cluster Omega Centauri. Searching through the 1.7 billion stars observed by the ESA Gaia mission, they have identified 309 stars that suggest that this globular cluster may actually be the remnant of a dwarf galaxy that is being torn apart by the gravitational forces of our Galaxy.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 04/24/2019 09:28 pm
The 53rd ESLAB symposium that took place April 8 to 12 in ESTEC was dedicated to Gaia, set near the 1 year anniversary of Gaia DR2. There is a write up here

https://www.cosmos.esa.int/web/gaia/iow_20190418

Uploaded presentations from the conference are here

https://zenodo.org/communities/eslab53?page=1&size=20
Title: Re: ESA - Gaia updates
Post by: Star One on 05/31/2019 07:57 pm
eso1908 — Organisation Release

Pinpointing Gaia to Map the Milky Way

ESO’s VST helps determine the spacecraft’s orbit to enable the most accurate map ever of more than a billion stars
2 May 2019

Gaia, operated by the European Space Agency (ESA), surveys the sky from orbit to create the largest, most precise, three-dimensional map of our Galaxy. One year ago, the Gaia mission produced its much-awaited second data release, which included high-precision measurements — positions, distance and proper motions — of more than one billion stars in our Milky Way galaxy. This catalogue has enabled transformational studies in many fields of astronomy, addressing the structure, origin and evolution the Milky Way and generating more than 1700 scientific publications since its launch in 2013.

In order to reach the accuracy necessary for Gaia’s sky maps, it is crucial to pinpoint the position of the spacecraft from Earth. Therefore, while Gaia scans the sky, gathering data for its stellar census, astronomers regularly monitor its position using a global network of optical telescopes, including the VST at ESO’s Paranal Observatory [1]. The VST is currently the largest survey telescope observing the sky in visible light, and records Gaia’s position in the sky every second night throughout the year.

“Gaia observations require a special observing procedure,” explained Monika Petr-Gotzens, who has coordinated the execution of ESO’s observations of Gaia since 2013. “The spacecraft is what we call a ‘moving target’, as it is moving quickly relative to background stars — tracking Gaia is quite the challenge!”

“The VST is the perfect tool for picking out the motion of Gaia,” elaborated Ferdinando Patat, head of the ESO’s Observing Programmes Office. “Using one of ESO’s first-rate ground-based facilities to bolster cutting-edge space observations is a fine example of scientific cooperation.”

“This is an exciting ground-space collaboration, using one of ESO’s world-class telescopes to anchor the trailblazing observations of ESA’s billion star surveyor,” commented Timo Prusti, Gaia project scientist at ESA.

The VST observations are used by ESA’s flight dynamics experts to track Gaia and refine the knowledge of the spacecraft’s orbit. Painstaking calibration is required to transform the observations, in which Gaia is just a speck of light among the bright stars, into meaningful orbital information. Data from Gaia’s second release was used to identify each of the stars in the field of view, and allowed the position of the spacecraft to be calculated with astonishing precision — up to 20 milliarcseconds.

“This is a challenging process: we are using Gaia’s measurements of the stars to calibrate the position of the Gaia spacecraft and ultimately improve its measurements of the stars,” explains Timo Prusti.

“After careful and lengthy data processing, we have now achieved the accuracy required for the ground-based observations of Gaia to be implemented as part of the orbit determination,” says Martin Altmann, lead of the Ground Based Optical Tracking (GBOT) campaign at the Centre for Astronomy of Heidelberg University, Germany.

The GBOT information will be used to improve our knowledge of Gaia’s orbit not only in observations to come, but also for all the data that have been gathered from Earth in the previous years, leading to improvements in the data products that will be included in future releases.
Title: Re: ESA - Gaia updates
Post by: eeergo on 07/15/2019 10:49 pm
Eclipse avoidance thrust vectoring ops are on tomorrow for Gaia:

https://twitter.com/esaoperations/status/1150780813186916357
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 08/29/2019 10:11 pm
Gaia untangles the starry strings of the Milky Way

http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_untangles_the_starry_strings_of_the_Milky_Way

Also a video comes with this release

https://www.youtube.com/watch?v=NJOAzj7b6bQ
Title: Re: ESA - Gaia updates
Post by: Star One on 10/23/2019 04:43 pm
Gaia astronomical revolution:

https://youtu.be/Q_SnUBqXTEs
Title: Re: ESA - Gaia updates
Post by: Star One on 01/08/2020 08:51 am
Quote
Astronomers at Harvard University have discovered a monolithic, wave-shaped gaseous structure—the largest ever seen in our galaxy—made up of interconnected stellar nurseries. Dubbed the "Radcliffe wave" in honor of the collaboration's home base, the Radcliffe Institute for Advanced Study, the discovery transforms a 150-year-old vision of nearby stellar nurseries as an expanding ring into one featuring an undulating, star-forming filament that reaches trillions of miles above and below the galactic disk.

The work, published in Nature on 7 January, was enabled by a new analysis of data from the European Space Agency's Gaia spacecraft, launched in 2013 with the mission of precisely measuring the position, distance, and motion of the stars. The research team combined the super-accurate data from Gaia with other measurements to construct a detailed, 3-D map of interstellar matter in the Milky Way, and noticed an unexpected pattern in the spiral arm closest to the Earth.

Quote
"We don't know what causes this shape but it could be like a ripple in a pond, as if something extraordinarily massive landed in our galaxy," said Alves. "What we do know is that our Sun interacts with this structure. It passed by a festival of supernovae as it crossed Orion 13 million years ago, and in another 13 million years it will cross the structure again, sort of like we are 'surfing the wave'."

https://phys.org/news/2020-01-milky-reveals-giant-stellar-nurseries.amp

Here’s the related paper:

https://www.nature.com/articles/s41586-019-1874-z
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/08/2020 06:39 pm
So, the Gould Belt is no more but instead the Radcliffe wave? We'll see

Another interesting Gaia related result today: It measured the distance to a newly discovered star cluster created by the Magellanic Stream. Actually more like data mining Gaia pulled out the cluster which turns out related to the Magellanic Stream:

https://www.simonsfoundation.org/2020/01/07/milky-way-new-stars/
Title: Re: ESA - Gaia updates
Post by: jacqmans on 01/21/2020 08:32 am
Global Gaia campaign reveals secrets of stellar pair
21/01/2020

A 500-day global observation campaign spearheaded more than three years ago by ESA’s galaxy-mapping powerhouse Gaia has provided unprecedented insights into the binary system of stars that caused an unusual brightening of an even more distant star.

The brightening of the star, located in the Cygnus constellation, was first spotted in August 2016 by the Gaia Photometric Science Alerts programme.

This system, maintained by the Institute of Astronomy at the University of Cambridge, UK, scans daily the huge amount of data coming from Gaia and alerts astronomers to the appearance of new sources or unusual brightness variations in known ones, so that they can quickly point other ground and space-based telescopes to study them in detail. The phenomena may include supernova explosions and other stellar outbursts.

http://www.esa.int/Science_Exploration/Space_Science/Gaia/Global_Gaia_campaign_reveals_secrets_of_stellar_pair
Title: Re: ESA - Gaia updates
Post by: jacqmans on 01/21/2020 08:33 am
https://youtu.be/-Bhk8_SNjlk
Title: Re: ESA - Gaia updates
Post by: bolun on 03/04/2020 07:39 pm
The Milky Way's Warp

The structure of our galaxy, the Milky Way, with its warped galactic disc, where the majority of its hundreds of billions of stars reside. Data from ESA's star-observer Gaia recently proved that the disc's warp is precessing, essentially moving around similarly to a wobbling spinning top. The speed of the warp's rotation is so high that it must have been caused by a rather powerful event, astronomers believe, perhaps an ongoing collision with another, smaller, galaxy which sends ripples through the disc like a rock thrown into water.

Related article: Milky Way’s warp caused by galactic collision, Gaia suggests (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Milky_Way_s_warp_caused_by_galactic_collision_Gaia_suggests)

https://www.esa.int/ESA_Multimedia/Images/2020/01/The_Milky_Way_s_Warp

Image credit: Stefan Payne-Wardenaar; Inset: NASA/JPL-Caltech; Layout: ESA
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 04/11/2020 05:37 am
This is a little old now, but it is quite interesting

New asteroid models from Gaia and Lowell data:

https://arxiv.org/abs/1909.09395

Quote


Rotation properties (spin-axis direction and rotation period) and coarse shape models of asteroids can be reconstructed from their disk-integrated brightness when measured from various viewing geometries. These physical properties are essential for creating a global picture of structure and dynamical evolution of the main belt. The number of shape and spin models can be increased not only when new data are available, but also by combining independent data sets and inverting them together. Our aim was to derive new asteroid models by processing readily available photometry. We used asteroid photometry compiled in the Lowell Observatory photometry database with photometry from the Gaia Data Release 2. Both data sources are available for about 5400 asteroids. In the framework of the Asteroids@home distributed computing project, we applied the light curve inversion method to each asteroid to find its convex shape model and spin state that fits the observed photometry. Due to the limited number of Gaia DR2 data points and poor photometric accuracy of Lowell data, we were able to derive unique models for only ~1100 asteroids. Nevertheless, 762 of these are new models that significantly enlarge the current database of about 1600 asteroid models. Our results demonstrate the importance of a combined approach to inversion of asteroid photometry. While our models in general agree with those obtained by separate inversion of Lowell and Gaia data, the combined inversion is more robust, model parameters are more constrained, and unique models can be reconstructed in many cases when individual data sets alone are not sufficient.


So the MPC has 930,000+ objects, both in the inner and outer solar system, Asteroids@home which is where this paper is from has added 762 to the current 1600 models (so ~2,300 models) and spacecraft has visited 20 to 30 minor bodies. The minor bodies of the solar system are still mostly unknown
Title: Re: ESA - Gaia updates
Post by: bolun on 05/26/2020 01:20 pm
GALACTIC CRASH MAY HAVE TRIGGERED SOLAR SYSTEM FORMATION

25 May 2020

The formation of the Sun, the Solar System and the subsequent emergence of life on Earth may be a consequence of a collision between our galaxy, the Milky Way, and a smaller galaxy called Sagittarius, discovered in the 1990s to be orbiting our galactic home.

Astronomers have known that Sagittarius repeatedly smashes through the Milky Way's disc, as its orbit around the galaxy's core tightens as a result of gravitational forces. Previous studies suggested that Sagittarius, a so called dwarf galaxy, had had a profound effect on how stars move in the Milky Way. Some even claim that the 10 000 times more massive Milky Way's trademark spiral structure might be a result of the at least three known crashes with Sagittarius over the past six billion years.

A new study, based on data gathered by ESA's galaxy mapping powerhouse Gaia, revealed for the first time that the influence of Sagittarius on the Milky Way may be even more substantial. The ripples caused by the collisions seem to have triggered major star formation episodes, one of which roughly coincided with the time of the formation of the Sun some 4.7 billion years ago.

https://sci.esa.int/s/WyMonjW

Image credit: ESA
Title: Re: ESA - Gaia updates
Post by: Star One on 05/27/2020 08:55 am
This is the actual paper related to the above.

The recurrent impact of the Sagittarius dwarf on the star formation history of the Milky Way

Abstract
Satellites orbiting disk galaxies can induce phase space features such as spirality, vertical heating and phase-mixing in their disks. Such features have also been observed in our own Galaxy, but the complexity of the Milky Way disk has only recently been fully mapped by Gaia Data Release 2 (DR2) data. This complex behaviour is mainly ascribed to repeated perturbations induced by the Sagittarius dwarf galaxy (Sgr) along its orbit, pointing to this satellite as the main dynamical architect of the Milky Way disk. Here, we model Gaia DR2-observed colour–magnitude diagrams to obtain a detailed star formation history of the ~2 kpc bubble around the Sun. It reveals three conspicuous and narrow episodes of enhanced star formation that we can precisely date as having occurred 5.7, 1.9 and 1.0 Gyr ago. The timing of these episodes coincides with proposed Sgr pericentre passages according to (1) orbit simulations, (2) phase space features in the Galactic disk and (3) Sgr stellar content. These findings most probably suggest that Sgr has also been an important actor in the build-up of the stellar mass of the Milky Way disk, with the perturbations from Sgr repeatedly triggering major episodes of star formation.

https://www.nature.com/articles/s41550-020-1097-0
Title: Re: ESA - Gaia updates
Post by: jacqmans on 07/02/2020 12:11 pm
Gaia revolutionises asteroid tracking

01/07/2020

ESA’s Gaia space observatory is an ambitious mission to construct a three-dimensional map of our galaxy by making high-precision measurements of over one billion stars. However, on its journey to map distant suns, Gaia is revolutionising a field much closer to home. By accurately mapping the stars, it is helping researchers track down lost asteroids.

https://www.esa.int/Safety_Security/Gaia_revolutionises_asteroid_tracking
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 09/21/2020 10:47 pm
It seems people have missed it here: Gaia EDR3 will take place on December 3rd 2020. Here is the overview page:

https://www.cosmos.esa.int/web/gaia/early-data-release-3
Title: ESA - Gaia updates
Post by: Star One on 11/20/2020 10:42 am
Quote
So Caballero repeated the search, looking for Sun-like stars among the thousands that have been identified by Gaia in this region of the sky. By Sun-like, he means stars that share the same temperature, radius and luminosity.

The search returned just one candidate. “The only potential Sun-like star in all the WOW! Signal region appears to be 2MASS 19281982-2640123,” says Caballero. This star sits in the constellation of Sagittarius at a distance of 1800 light-years. It is an identical twin to our Sun, with the same temperature, radius, and luminosity.

Of course, Caballero’s work does not mean that 2MASS 19281982-2640123 must have been the source. He points out that there are many stars in that region of the sky that are too dim to be included in the catalog. One of these could be the source.

https://www.discovermagazine.com/the-sciences/sun-like-star-identified-as-the-potential-source-of-the-wow-signal

An approximation to determine the source of the WOW! Signal

In this paper it is analysed which of the thousands of stars in the WOW! Signal region could have the highest chance of being the real source of the signal, providing that it came from a star system similar to ours. A total of 66 G and K-type stars are sampled, but only one of them is identified as a potential Sun-like star considering the available information in the Gaia Archive. This candidate source, which is named 2MASS 19281982-2640123, therefore becomes an ideal target to conduct observations in the search for potentially habitable exoplanets. Another 14 potential Sun-like stars (with estimated temperatures between 5,730 and 5,830 K) are also found in the region, but information about their luminosity and radius is unknown.

https://arxiv.org/abs/2011.06090
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 11/24/2020 11:31 pm
Milky Way family tree

https://www.uni-heidelberg.de/en/newsroom/milky-way-family-tree

While this Heidelberg release does not mention the surveys, other releases that come to that conclusion they used Gaia + APOGEE + RAVE + several other surveys
Title: Re: ESA - Gaia updates
Post by: jacqmans on 12/03/2020 09:37 am
DLR Press Release, 03 December 2020

Our galaxy in 3D: Gaia satellite mission maps the Milky Way - New instalment of the largest star catalogue ever published


Full article with image: https://www.dlr.de/content/en/articles/news/2020/04/20201203_gaia_satellite_mission_maps_the_milky_way.html

The Gaia mission is engaged in an ambitious project – the creation of the most extensive and accurate star catalogue of all time. The first instalment of the catalogue’s third data release – the Gaia Early Data Release 3 (Gaia EDR3) – was published on 3 December 2020. “This marks another step towards our objective of completing a high-precision, three-dimensional optical survey of the entire sky,” says Walther Pelzer, Member of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Executive Board and Head of the DLR Space Administration. “Gaia is gathering information on the positions and velocities of approximately two billion objects in the Milky Way and distant galaxies. It has already proven itself extremely successful at this task so far. With a total data volume of around one petabyte, Gaia will also help to strengthen the expertise of German academia and industry in the fields of Big Data processing, machine learning and artificial intelligence, as well as providing us with entirely new insights into the number, composition and distribution of stars and other celestial bodies.”

The aim of Gaia, which launched in December 2013, is to determine the position, proper motion, distance and brightness of almost two billion celestial bodies – including roughly one percent of the stars in our Galaxy. These are important parameters for determining the nature of objects and how their properties evolve over time. At the same time, this information is being used to create a three-dimensional star map with an unprecedented level of accuracy. “The first two data releases were published in September 2016 and April 2018 and have had a lasting impact on our understanding of the Milky Way’s development,” explains Alessandra Roy, Gaia Project Manager at the DLR Space Administration. “So far, 1.8 billion celestial bodies are listed in the combined data catalogue. Measurements relating to the proper motion and distance of the majority of these bodies – approximately 1.5 billion of them– have now been significantly improved.”

The first instalment of the third data release contains information about fainter stars in the vicinity of the Sun, areas in the outer regions of the Milky Way and stars in the Magellanic Clouds. It also features measurements of our Solar System’s acceleration relative to the rest of the galaxy. The quality of this new data is so high that scientists expect further advances to be made in research into the structure, dynamics and history of the Milky Way, and the wider study of the Universe as a whole.
For all of the research institutions that have signed the ZEMA agreement, the statement also marks a commitment to developing sustainable aviation that meets the needs of society.

The field of astronomy concerned with measuring and calculating the positions and motions of celestial bodies is called astrometry. It dates back over 5000 years, but it was only with ESA’s Hipparcos satellite in the 1990s, and now with Gaia in particular, that precision astrometry has begun. In order to produce the final Gaia catalogue, scientists have to simultaneously solve around ten billion equations and process over a petabyte of data. If the data in this catalogue were to be printed, the collection of books required to hold it would form a pile 100 kilometres high. On average, Gaia observes 850 million objects and produces 20 gigabytes of data every day.

Originally, the Gaia mission was scheduled to end in 2019. However, as all of the onboard instruments are still fully functional, the aim now is for the mission to continue gathering data until 2025. By this time, its supply of gas, which it uses to align itself, is likely to have been completely used up. The more extensive publication of the third Gaia Data Release (Gaia DR3) is scheduled for the first half of 2022. “In all likelihood, it will be a long time before we see a space mission comparable to Gaia,” says Roy. “At the moment, scientists are conducting studies with a view to designing an astrometry mission that also covers the infrared region of the electromagnetic spectrum, but the technology required for this has not yet been adequately developed.”

Gaia is a European Space Agency (ESA) mission involving over 20 countries, including Germany. Germany leads the coordination unit responsible for determining the astrometric results as part of the Gaia Data Processing and Analysis Consortium (DPAC). The German contribution, which is financed by the DLR Space Administration with funding from the German Federal Ministry for Economic Affairs and Energy (BMWi), involves the Astronomical Calculation Institute (University of Heidelberg), the Leibniz Institute for Astrophysics Potsdam, the Max Planck Institute for Astronomy (Heidelberg) and the Lohrmann Observatory at TU Dresden. The DLR Space Administration acts as the German national space agency. The Max Planck Institute for Astrophysics (Garching) will be involved in spectroscopic data analysis for the third data release. Hamburg Observatory and the University of Bremen were also involved in the first data release of the catalogue.
Title: Re: ESA - Gaia updates
Post by: jacqmans on 12/03/2020 09:40 am
Gaia’s new data takes us to the Milky Way’s anticentre and beyond

03/12/2020

The motion of stars in the outskirts of our galaxy hints at significant changes in the history of the Milky Way. This and other equally fascinating results come from a set of papers that demonstrate the quality of ESA’s Gaia Early third Data Release (EDR3), which is made public today.

Astronomers from the Gaia Data Processing and Analysis Consortium (DPAC) saw the evidence of the Milky Way’s past by looking at stars in the direction of the galaxy’s ‘anticentre’. This is in the exact opposite direction on the sky from the centre of the galaxy.

The results on the anticentre come from one of the four ‘demonstration papers’ released alongside the Gaia data. The others use Gaia data to provide a huge extension to the census of nearby stars, derive the shape of the Solar System’s orbit around the centre of the galaxy, and probe structures in two nearby galaxies to the Milky Way. The papers are designed to highlight the improvements and quality of the newly published data.

What’s new in EDR3?

Gaia EDR3 contains detailed information on more than 1.8 billion sources, detected by the Gaia spacecraft. This represents an increase of more than 100 million sources over the previous data release (Gaia DR2), which was made public in April 2018. Gaia EDR3 also contains colour information for around 1.5 billion sources, an increase of about 200 million sources over Gaia DR2. As well as including more sources, the general accuracy and precision of the measurements has also improved.

“The new Gaia data promise to be a treasure trove for astronomers,” says Jos de Bruijne, ESA’s Gaia Deputy Project Scientist.

The density of stars from Gaia’s Early Data Release 3The density of stars from Gaia’s Early Data Release 3
Gaia’s view of the Milky Way’s neighbouring galaxiesGaia’s view of the Milky Way’s neighbouring galaxies


To the galactic anticentre

The new Gaia data have allowed astronomers to trace the various populations of older and younger stars out towards the very edge of our galaxy – the galactic anticentre. Computer models predicted that the disc of the Milky Way will grow larger with time as new stars are born. The new data allow us to see the relics of the 10 billion-year-old ancient disc and so determine its smaller extent compared to the Milky Way’s current disc size.

The new data from these outer regions also strengthen the evidence for another major event in the more recent past of the galaxy.

The data show that in the outer regions of the disc there is a component of slow-moving stars above the plane of our galaxy that are heading downwards towards the plane, and a component of fast-moving stars below the plane that are moving upwards. This extraordinary pattern had not been anticipated before. It could be the result of the near-collision between the Milky Way and the Sagittarius dwarf galaxy that took place in our galaxy’s more recent past.

https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_s_new_data_takes_us_to_the_Milky_Way_s_anticentre_and_beyond
Title: Re: ESA - Gaia updates
Post by: jacqmans on 12/03/2020 09:46 am
https://youtu.be/59k7aceKRZY
Title: Re: ESA - Gaia updates
Post by: jacqmans on 12/03/2020 09:46 am
https://youtu.be/nFEzzIufnVI
Title: Re: ESA - Gaia updates
Post by: jacqmans on 12/03/2020 09:49 am
Title: Re: ESA - Gaia updates
Post by: ugordan on 12/03/2020 10:36 am
https://youtu.be/nFEzzIufnVI

Much better quality version on Gaia youtube channel:

https://www.youtube.com/watch?v=k9pHGhNtyPk
Title: Re: ESA - Gaia updates
Post by: ugordan on 12/03/2020 10:55 am
https://www.cosmos.esa.int/web/gaia/edr3-acceleration-solar-system

Quote
In the Gaia EDR3 science verification paper "Gaia Early Data Release 3: Acceleration of the solar system from Gaia astrometry" it was found that the amplitude of the pattern is about 5 micro-arcsecond per year which corresponds to an acceleration of about 0.23 nanometer/s2 towards the point with celestial coordinates (alpha ~ 269.1 deg, delta ~ -31.6 deg), within a few degrees from the Galactic Centre.

In one second of time, this tiny acceleration causes a deflection of the solar system’s trajectory of about 0.1 nanometer towards the galactic centre, some 26,000 light years away. Not to be forgotten here is that the solar system barycentre is moving around the galactic centre with a velocity of about 220 km/s, and that the combination of a large velocity with a pull from the galactic centre results in an orbit. To put things into perspective: the acceleration of the Sun towards the barycenter of the solar system is up to 250 nanometer/s2 (so ~1000 times bigger).

The level of precision Gaia has demonstrated still boggles my mind to this day.
To put this in perspective, we're talking about measuring the curvature of an orbit arc that is roughly equivalent to trying to measure the curvature of the Earth based on half a meter of its circumference.
Title: Re: ESA - Gaia updates
Post by: Star One on 12/07/2020 02:59 pm
Article about EDR3 & some of the uses it’s being put to.

https://www.scientificamerican.com/article/fresh-data-from-gaia-galaxy-survey-gives-best-map-ever-of-the-milky-way/
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 12/07/2020 11:16 pm
The release documentation is here: https://gea.esac.esa.int/archive/documentation/GEDR3/index.html

Huge read but what I read is very interesting. I have also see three of the unravelling event videos, specifically the three in English from the Royal Astronomical Society, the processing unit in Geneva and the one from Leiden in English for the South Americans. Different presenters but they say 95% the same things, with slight difference on the emphasis due to who is speaking. I thought I would want to see the French event, but I doubt it will say anything more. The reason we are seeing a release now is that they wanted one every two years, hence they released the parts that were completed early. Pre launch they wanted to do a release every year but apparently computers have not advanced enough to be able to do this timely. What they released now was more or less the same products from DR1 since their data pipelines are mature enough so that with a few tweaks to correct systematic errors and improve capacity they could handle the extra data. What they had though as more of a demonstration product for DR2 will be released much improved with the full DR3 in early 2022. They can handle close binaries that are closer than those in DR2 but still, there were radial velocities in DR2 that were for very close binaries and in EDR3 they caught the other pair, which is why they are releasing the same DR2 velocities but deleted for these pairs and for spurious crowded region matches. There are still systematic issues such as negative parallaxes but much reduced. The checkerboard pattern is reduced, but still exists. Apparently the distances to clusters differ from independent measurements based on magnitude and these are just among the known issues to those that released the data. Just like with the previous data releases the community will find other systematic issues with the release. Honestly though, the more you read, the more you are impressed by all the work and the effort to improve the quality. I would really have liked if we had the 100,000 asteroids, but these are coming out with the full DR3. Now if they do manage to keep their pace, something will be released in 2024, whether a full DR4 or an EDR4 is of course unknown. DR4 is when you get exoplanets. We are in 2020 and EDR3 has data up to 2017. DR3 in 2022 will again have data to 2017. The 2024 release will at most have 2020 data, most likely per my educated guess no, which begets the question: if the mission does last up to 2025 when consumables give out, when will that data get released? If there is GaiaNIR, the proposed follow up mission, when would that get launched. At least though in this release based on better calibration of their sensors and a quieter sun that has not degraded the electronics as much as was expected they have managed to meet the original quality criteria, which seemed unlikely due to unforeseen spacecraft issues.
Title: Re: ESA - Gaia updates
Post by: Star One on 01/20/2021 10:03 am
String of stars in Milky Way are related

Examination of Theia 456 finds its nearly 500 stars were born at same time

https://news.northwestern.edu/stories/2021/01/string-of-stars-in-milky-way-are-related/
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 02/28/2021 07:15 am
The first Gaia DR4 data:

https://www.cosmos.esa.int/web/gaia/iow_20210226

After they cleared out the easy parts of DR3 through EDR3, they have started working on DR4. Since the plan is to release every two years something, the earliest we will see DR4 is in 2022
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 03/13/2021 07:41 am
GaiaNIR White Paper

https://link.springer.com/article/10.1007/s10686-021-09705-z

It is an open access paper. GaiaNIR is the proposed follow up to Gaia with two NIR channels so it can pierce dust clouds. Original Gaia maximized the size possible for the rocket and apparently they are happy with the telescopes and general configuration of the optics, implying that they again plan for a Soyuz launch. Marginal improvements in the telescopes, more channels and data, likely more pixels in the detectors meaning less saturation and expecting to measure 5 times as many stars. Time frame, about 20 years in the future. Gaia is the ESA non earth observation mission downloading the most data and the processing consortium discovered that its computers while state of the art are just not good enough for an annual release, though that also has to do with creating and coding the algorithms. GaiaNIR 20 years in the future likely means lasercom and 7 generations meaning 2^7=128 times faster computers, if Moore's law holds. If it is not 128 times more data, we might just see faster releases if/when this gets launched.
Title: ESA - Gaia updates
Post by: Star One on 03/13/2021 09:40 am
GaiaNIR White Paper

https://link.springer.com/article/10.1007/s10686-021-09705-z

It is an open access paper. GaiaNIR is the proposed follow up to Gaia with two NIR channels so it can pierce dust clouds. Original Gaia maximized the size possible for the rocket and apparently they are happy with the telescopes and general configuration of the optics, implying that they again plan for a Soyuz launch. Marginal improvements in the telescopes, more channels and data, likely more pixels in the detectors meaning less saturation and expecting to measure 5 times as many stars. Time frame, about 20 years in the future. Gaia is the ESA non earth observation mission downloading the most data and the processing consortium discovered that its computers while state of the art are just not good enough for an annual release, though that also has to do with creating and coding the algorithms. GaiaNIR 20 years in the future likely means lasercom and 7 generations meaning 2^7=128 times faster computers, if Moore's law holds. If it is not 128 times more data, we might just see faster releases if/when this gets launched.
I can’t see them still using Soyuz as a launcher in twenty years time. On that kind of timescale I expect to see a very different launcher market so it’s curious they treat this as a static item in the paper.
Title: Re: ESA - Gaia updates
Post by: russianhalo117 on 03/13/2021 08:44 pm
GaiaNIR White Paper

https://link.springer.com/article/10.1007/s10686-021-09705-z

It is an open access paper. GaiaNIR is the proposed follow up to Gaia with two NIR channels so it can pierce dust clouds. Original Gaia maximized the size possible for the rocket and apparently they are happy with the telescopes and general configuration of the optics, implying that they again plan for a Soyuz launch. Marginal improvements in the telescopes, more channels and data, likely more pixels in the detectors meaning less saturation and expecting to measure 5 times as many stars. Time frame, about 20 years in the future. Gaia is the ESA non earth observation mission downloading the most data and the processing consortium discovered that its computers while state of the art are just not good enough for an annual release, though that also has to do with creating and coding the algorithms. GaiaNIR 20 years in the future likely means lasercom and 7 generations meaning 2^7=128 times faster computers, if Moore's law holds. If it is not 128 times more data, we might just see faster releases if/when this gets launched.
I can’t see them still using Soyuz as a launcher in twenty years time. On that kind of timescale I expect to see a very different launcher market so it’s curious they treat this as a static item in the paper.
it is just a baselined launcher. You don't list launchers that are not in service that are in design.
Title: Re: ESA - Gaia updates
Post by: sdsds on 03/13/2021 08:58 pm
it is just a baselined launcher. You don't list launchers that are not in service that are in design.

But it looks like the whole point of a mission at a different  wavelength λ is predicated on being unable to increase the aperture D. Because "the telescope’s angular resolution (i.e. minimum angular separation) R ∝ λ/D."

If a new launcher with a very large payload bay reduced the cost of increasing D is isn't clear the best approach is to decrease λ.
Title: Re: ESA - Gaia updates
Post by: yoram on 03/13/2021 09:38 pm
GaiaNIR White Paper

https://link.springer.com/article/10.1007/s10686-021-09705-z

It is an open access paper. GaiaNIR is the proposed follow up to Gaia with two NIR channels so it can pierce dust clouds. Original Gaia maximized the size possible for the rocket and apparently they are happy with the telescopes and general configuration of the optics, implying that they again plan for a Soyuz launch. Marginal improvements in the telescopes, more channels and data, likely more pixels in the detectors meaning less saturation and expecting to measure 5 times as many stars. Time frame, about 20 years in the future. Gaia is the ESA non earth observation mission downloading the most data and the processing consortium discovered that its computers while state of the art are just not good enough for an annual release, though that also has to do with creating and coding the algorithms. GaiaNIR 20 years in the future likely means lasercom and 7 generations meaning 2^7=128 times faster computers, if Moore's law holds. If it is not 128 times more data, we might just see faster releases if/when this gets launched.

What exactly are they doing in those 20 years? Surely it cannot take that long to slightly update an existing space craft.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 03/14/2021 05:32 am


What exactly are they doing in those 20 years? Surely it cannot take that long to slightly update an existing space craft.

[/quote]

It did take 20 years to go from HIPPARCOS to Gaia. They are using their computer resources to actually create the Gaia catalogue. While I have not read the original Gaia proposal, I am pretty sure it looked more like HIPPARCOS than what Gaia did eventually look like. Also they say that they need technology to advance to create time integration NIR sensors good enough and since they would like to keep it as an M class mission they would rather bring on board the Americans or the Japanese who are more advanced in these sensors.
Title: Re: ESA - Gaia updates
Post by: Alpha_Centauri on 03/14/2021 08:26 am
it is just a baselined launcher. You don't list launchers that are not in service that are in design.

But it looks like the whole point of a mission at a different  wavelength λ is predicated on being unable to increase the aperture D. Because "the telescope’s angular resolution (i.e. minimum angular separation) R ∝ λ/D."

If a new launcher with a very large payload bay reduced the cost of increasing D is isn't clear the best approach is to decrease λ.

The telescope size has nothing to do with the move to infrared. It has long been desired to do astrometry in the infrared because the volume of space/number/type of stars you can access is far larger and less biased than in the optical.  Hipparcos and Gaia were optical because that is what detector technology allowed.

Even with US or Japanese involvement, as an institutional mission there will have to be a European backup launcher, and I can't see Europe using extra-large fairings any time soon.
Title: Re: ESA - Gaia updates
Post by: Dizzy_RHESSI on 03/15/2021 03:32 pm
What exactly are they doing in those 20 years? Surely it cannot take that long to slightly update an existing space craft.

The longer the separation is between Gaia and GaiaNIR, the better the measurements of proper motions will be. If you observe over a longer baseline in time the change in angular position becomes larger. But the real reason is simply the timing of mission opportunities. Slots for ESA's Cosmic Vision program have already been filled, and the next opportunities to open up will not see a mission fly before ~2040. The science theme of astrometry was submitted to the L2/L3 selection, but it was unsuccessful. These opportunities are far too competitive to fly two astrometry missions back-to-back. It could happen as a NASA mission sooner, but I think that's quite unlikely given that it would fall in the gap between strategic missions and MIDEX/SMEX competitions.
Title: Re: ESA - Gaia updates
Post by: Star One on 03/16/2021 09:04 am
There Should be About 7 Interstellar Objects Passing Through the Inner Solar System Every Year.

Interstellar Objects in the Solar System: 1. Isotropic Kinematics from the Gaia Early Data Release 3

1I/'Oumuamua (or 1I) and 2I/Borisov (or 2I), the first InterStellar Objects (ISOs) discovered passing through the solar system, have opened up entirely new areas of exobody research. Finding additional ISOs and planning missions to intercept or rendezvous with these bodies will greatly benefit from knowledge of their likely orbits and arrival rates. Here, we use the local velocity distribution of stars from the Gaia Early Data Release 3 Catalogue of Nearby Stars and a standard gravitational focusing model to predict the velocity dependent flux of ISOs entering the solar system. With an 1I-type ISO number density of ∼0.1 AU−3, we predict that a total of ∼6.9 such objects per year should pass within 1 AU of the Sun. There will be a fairly large high-velocity tail to this flux, with half of the incoming ISOs predicted to have a velocity at infinity, v∞, &gt; 40 km s−1. Our model predicts that ∼92\% of incoming ISOs will be residents of the galactic thin disk, ∼6\% (∼4 per decade) will be from the thick disk, ∼1 per decade will be from the halo and at most ∼3 per century will be unbound objects, ejected from our galaxy or entering the Milky Way from another galaxy. The rate of ISOs with very low v∞  1.5 km s−1 is so low in our model that any incoming very low velocity ISOs are likely to be previously lost solar system objects. Finally, we estimate a cometary ISO number density of ∼7 × 10−5 AU−3 for 2I type ISOs, leading to discovery rates for these objects possibly approaching once per decade with future telescopic surveys.

https://arxiv.org/abs/2103.03289

https://www.universetoday.com/150478/there-should-be-about-7-interstellar-objects-passing-through-the-inner-solar-system-every-year/
Title: Re: ESA - Gaia updates
Post by: bolun on 04/09/2021 04:07 pm
12 RARE EINSTEIN CROSSES DISCOVERED WITH GAIA

7 April 2021

Thanks to ESA's star mapping spacecraft Gaia and machine learning, astronomers have discovered 12 quasars whose light is so strongly deflected by foreground galaxies that they are each visible as four distinct images, called an 'Einstein cross'. These crosses are unique tools to learn more about dark matter and the expansion rate of the Universe.

https://sci.esa.int/s/8kJm5gW

Credits: The GraL Collaboration & R. Hurt (IPAC/Caltech)/The GraL Collaboration
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 05/13/2021 09:35 pm
Gaia Might Even be Able to Detect the Gravitational Wave Background of the Universe

https://www.universetoday.com/151177/gaia-might-even-be-able-to-detect-the-gravitational-wave-background-of-the-universe/

There is also another news item today which I have not been able to access today being behind the agency firewall about using LAMOST to improve accuracy
Title: Re: ESA - Gaia updates
Post by: Star One on 05/26/2021 03:17 pm
Quote
The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) has helped Gaia achieve millimagnitude (mmag) precision in photometry, according to a study led by researchers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) and Beijing Normal University (BNU)

https://eurekalert.org/pub_releases/2021-05/caos-lhg051121.php
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 06/25/2021 05:07 am
Gaia is still the gift that keeps on giving. There was a paper on arxiv that I got to though via twitter about mapping the Local Group of Galaxies membership, their relationship and what globular clusters belong to which galaxy (including finding new ones) based on Gaia maps. But this is not what I am here to share.

Gaia Coordination Unit 3 met recently and then created a video to explain to the general public what they do:

https://www.youtube.com/watch?v=s-jsPiTlfDk

What they do is create the catalog of stars and the scientists talk about how they calibrate the data, take into account relativistic effects and sensor / spacecraft calibration etc. Quite interesting
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/12/2021 07:09 am
This is a bit old news but no one has posted it here. Gaia discovered a cavity in the Milky Way galaxy:

https://www.cosmos.esa.int/web/gaia/iow_20210922
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/12/2021 07:28 am
Astrometric mass ratios of 248 long-period binary stars resolved in Hipparcos and Gaia EDR3

https://arxiv.org/abs/2109.11951

This is not a paper that got a press release but I found interesting. They begun with the 12005 double, 182 triple, and 8 quadruple star systems of the Double and Multiple System Annex to the main Hipparcos catalog which they had reprocessed in an earlier paper. They came to the conclusion using Gaia data that the quadruple stars are actually spurious but many of the triple were indeed triple. Since their program was for double starts (think three body problem) they rejected those and then compared doubles in both Hipparcos and Gaia to try to gauge orbital period in the 24.75 years between Hipparchos and EDR3. What I found downright awe inspiring is that the 248 number is what was reduced from the tens of thousands they begun not so much because of errors in making the catalogue shown by the comparison but because their QA/QC ratios showed that most likely there is an unseen companion not resolved by Gaia. If Proxima Centauri was at a few hundred light years it would be below the Gaia detection limit.

Gaia is to produce a very comprehensive catalog of stars up to 20th-21st magnitude or so. EDR3 and thus DR3 has 1.8 billion stars with the number somewhat increased from DR2 due to improvements at the bright end, the dim end, crowded regions but most importantly at multiple stars being resolved. Yes this paper shows that many of the higher order stars in the much more manageable Hipparcos Catalogue are even higher order with unresolved companions. While DR4 will be improved and might show some of these hidden companions, the authors suggest that GAIANIR, the followup mission in another 20 years, will be better for resolving several issues.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/16/2021 05:20 am
At the virtual European Astronomical Society meeting there were presentations on the full DR3 and they set up a page describing it here:

https://www.cosmos.esa.int/web/gaia/dr3

My special heart is for solar system objects so I saw the slides of the relevant presentation:

https://www.cosmos.esa.int/documents/29201/6953755/EAS2021-S15-Tanga.pdf/b9d68556-227a-b63a-ecac-c1716ea47cd7?t=1632305642371

There will be ca 158,000 of which 99.1% are already known, so few new asteroids. My guess is that they are still refining the discovery pipeline
Title: Re: ESA - Gaia updates
Post by: Yiosie on 11/27/2021 11:44 pm
Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_reveals_that_most_Milky_Way_companion_galaxies_are_newcomers_to_our_corner_of_space) [dated Nov. 24]

Quote
Data from ESA’s Gaia mission is re-writing the history of our galaxy, the Milky Way. What had traditionally been thought of as satellite galaxies to the Milky Way are now revealed to be mostly newcomers to our galactic environment.

A dwarf galaxy is a collection of between thousand and several billion stars. For decades it has been widely believed that the dwarf galaxies that surround the Milky Way are satellites, meaning that they are caught in orbit around our galaxy, and have been our constant companions for many billions of years. Now the motions of these dwarf galaxies have been computed with unprecedented precision thanks to data from Gaia’s early third data release and the results are surprising.

François Hammer, Observatoire de Paris - Université Paris Sciences et Lettres, France, and colleagues from across Europe and China, used the Gaia data to calculate the movements of 40 dwarf galaxies around the Milky Way. They did this by computing a set of quantities known as the three-dimensional velocities for each galaxy, and then using those to calculate the galaxy’s orbital energy and the angular (rotational) momentum.

They found that these galaxies are moving much faster than the giant stars and star clusters that are known to be orbiting the Milky Way. So fast, that they couldn’t be in orbit yet around the Milky Way, where interactions with our galaxy and its contents would have sapped their orbital energy and angular momentum.
Title: Re: ESA - Gaia updates
Post by: Arb on 11/28/2021 05:46 pm
Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_reveals_that_most_Milky_Way_companion_galaxies_are_newcomers_to_our_corner_of_space) [dated Nov. 24]

Quote
Data from ESA’s Gaia mission is re-writing the history of our galaxy, the Milky Way. What had traditionally been thought of as satellite galaxies to the Milky Way are now revealed to be mostly newcomers to our galactic environment.

A dwarf galaxy is a collection of between thousand and several billion stars. For decades it has been widely believed that the dwarf galaxies that surround the Milky Way are satellites, meaning that they are caught in orbit around our galaxy, and have been our constant companions for many billions of years. Now the motions of these dwarf galaxies have been computed with unprecedented precision thanks to data from Gaia’s early third data release and the results are surprising.

François Hammer, Observatoire de Paris - Université Paris Sciences et Lettres, France, and colleagues from across Europe and China, used the Gaia data to calculate the movements of 40 dwarf galaxies around the Milky Way. They did this by computing a set of quantities known as the three-dimensional velocities for each galaxy, and then using those to calculate the galaxy’s orbital energy and the angular (rotational) momentum.

They found that these galaxies are moving much faster than the giant stars and star clusters that are known to be orbiting the Milky Way. So fast, that they couldn’t be in orbit yet around the Milky Way, where interactions with our galaxy and its contents would have sapped their orbital energy and angular momentum.

The linked article is worth reading to the end - its penultimate paragraph includes this:
Quote
...in the traditional view that the Milky Way’s dwarfs were satellite galaxies that had been in orbit for many billions of years, it was assumed that they must be dominated by dark matter to balance the Milky Way’s tidal force and keep them intact. The fact that Gaia has revealed that most of the dwarf galaxies are circling the Milky Way for the first time means that they do not necessarily need to include any dark matter at all...

Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8 (https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8)
Title: Re: ESA - Gaia updates
Post by: ttle2 on 11/28/2021 06:13 pm
Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8 (https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8)

Like 99% of new astrophysics articles, it's available on arXiv: https://arxiv.org/abs/2109.11557
Title: Re: ESA - Gaia updates
Post by: deadman1204 on 11/28/2021 10:46 pm
Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8 (https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8)

Like 99% of new astrophysics articles, it's available on arXiv: https://arxiv.org/abs/2109.11557
Doesn't the arXiv only have the original submission? Not all the changes from review and such?
Title: Re: ESA - Gaia updates
Post by: ttle2 on 11/29/2021 06:03 am
Doesn't the arXiv only have the original submission? Not all the changes from review and such?

It depends, but usually people also upload the version that has been accepted to a journal (or in some cases they only post on arXiv after the paper has been accepted).  So in most cases the latest arXiv version is essentially the same as the published one. Layout etc. may of course be different.

In the case of 2109.11557, the comments of the latest (third) version say: "proof-corrected version for publication in The Astrophysical Journal, 2021, November", so what you see on arXiv is (at least content-wise) the same that you would find in the ApJ.
Title: Re: ESA - Gaia updates
Post by: Star One on 11/29/2021 10:34 am
Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_reveals_that_most_Milky_Way_companion_galaxies_are_newcomers_to_our_corner_of_space) [dated Nov. 24]

Quote
Data from ESA’s Gaia mission is re-writing the history of our galaxy, the Milky Way. What had traditionally been thought of as satellite galaxies to the Milky Way are now revealed to be mostly newcomers to our galactic environment.

A dwarf galaxy is a collection of between thousand and several billion stars. For decades it has been widely believed that the dwarf galaxies that surround the Milky Way are satellites, meaning that they are caught in orbit around our galaxy, and have been our constant companions for many billions of years. Now the motions of these dwarf galaxies have been computed with unprecedented precision thanks to data from Gaia’s early third data release and the results are surprising.

François Hammer, Observatoire de Paris - Université Paris Sciences et Lettres, France, and colleagues from across Europe and China, used the Gaia data to calculate the movements of 40 dwarf galaxies around the Milky Way. They did this by computing a set of quantities known as the three-dimensional velocities for each galaxy, and then using those to calculate the galaxy’s orbital energy and the angular (rotational) momentum.

They found that these galaxies are moving much faster than the giant stars and star clusters that are known to be orbiting the Milky Way. So fast, that they couldn’t be in orbit yet around the Milky Way, where interactions with our galaxy and its contents would have sapped their orbital energy and angular momentum.

The linked article is worth reading to the end - its penultimate paragraph includes this:
Quote
...in the traditional view that the Milky Way’s dwarfs were satellite galaxies that had been in orbit for many billions of years, it was assumed that they must be dominated by dark matter to balance the Milky Way’s tidal force and keep them intact. The fact that Gaia has revealed that most of the dwarf galaxies are circling the Milky Way for the first time means that they do not necessarily need to include any dark matter at all...

Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8 (https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8)
Things is does this result copy across to other galaxies as that would undermine the theory of Dark Matter I would have thought.
Title: Re: ESA - Gaia updates
Post by: deadman1204 on 11/29/2021 07:43 pm
Things is does this result copy across to other galaxies as that would undermine the theory of Dark Matter I would have thought.

Absolutely not. There are multiple independent lines of evidence supporting dark matter. All this means is that there isn't nearly as much dark matter in the satellite dwarf galaxies around the milky way than previously thought.
Title: Re: ESA - Gaia updates
Post by: bolun on 01/25/2022 03:19 pm
https://twitter.com/ESAGaia/status/1485892871106568193

Quote
Hello to @NASAWebb / @ESA_Webb / @csa_asc! Welcome to the neighbourhood here, beyond the Moon! Good to have you join us at L2. Let's watch the sky together.
Title: Re: ESA - Gaia updates
Post by: jebbo on 01/31/2022 05:32 pm
A nice teaser for the many Jupiter analogues expected in the next data release.

https://twitter.com/ESAGaia/status/1488140833962577925

--- Tony
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 02/09/2022 05:05 am
https://twitter.com/ESAGaia/status/1490674401561432070?cxt=HHwWjMCyzYye-K8pAAAA

Gaia DR3 is to be published Monday 13 June 2022 at 12:00 CEST.
Title: Re: ESA - Gaia updates
Post by: bolun on 02/17/2022 03:37 pm
Gaia reveals a new member of the Milky Way family

Our galaxy, the Milky Way, began forming around 12 billion years ago. Since then, it has been growing in both mass and size through a sequence of mergers with other galaxies.

Perhaps most exciting is that this process has not quite finished, and by using data from ESA’s Gaia spacecraft, astronomers can see it taking place. This in turn allows to reconstruct the history of our galaxy, revealing the ‘family tree’ of smaller galaxies that has helped make the Milky Way what it is today.

The latest work on this subject comes from Khyati Malhan, a Humboldt Fellow at the Max-Planck-Institut für Astronomie, Heidelberg, Germany, and colleagues. Together, they have analysed data based on Gaia’s early third data release (EDR3) looking for the remains of smaller galaxies merging with our own. These can be found in the so-called halo of the Milky Way, which surrounds the disc of younger stars and central bulge of older stars that comprise the more luminous parts of the Milky Way.

In total they studied 170 globular clusters, 41 stellar streams and 46 satellites of the Milky Way. Plotting them according to their energy and momentum revealed that 25 percent of these objects fall into six distinct groups. Each group is a merger taking place with the Milky Way. There was also a possible seventh merger in the data.

Five had been previously identified on surveys of stars. They are known as Sagittarius, Cetus, Gaia-Sausage/Enceladus, LMS-1/Wukong, and Arjuna/Sequoia/I’itoi. But the sixth was a newly identified merger event. The team called it Pontus, meaning the sea. In Greek mythology, Pontus is the name of one of the first children of Gaia, the Greek goddess of the Earth.

Based upon the way Pontus has been pulled apart by the Milky Way, Khyati and colleagues estimate that it probably fell into the Milky Way some eight to ten billion years ago. Four of the other five merger events likely also took place around this time as well. But the sixth event, Sagittarius, is more recent. It might have fallen into the Milky Way sometime in the last five to six billion years. As a result, the Milky Way has not yet been able to completely disrupt it.

Piece by piece, astronomers are fitting together the merger history of the Galaxy, and Gaia data is proving invaluable.

On 13 June 2022, the Gaia mission will issue its data release 3, which will provide even more detailed information about the Milky Way’s past, present, and future.

Image description:

This image shows the Milky Way as seen by Gaia. The squares represent the location of globular clusters, the triangles the location of satellite galaxies, and the small dots are stellar streams. The dots and squares in purple are objects brought into the Milky Way by the Pontus merging galaxy.

This research by Khyati Malhan was published in The Astrophysical Journal. DOI: https://iopscience.iop.org/article/10.3847/1538-4357/ac4d2a

https://www.esa.int/ESA_Multimedia/Images/2022/02/Gaia_reveals_a_new_member_of_the_Milky_Way_family

Image credit: ESA/Gaia/DPAC
Title: Re: ESA - Gaia updates
Post by: bolun on 03/16/2022 08:55 pm
Gaia snaps photo of Webb (zoom)

Images of the James Webb Space Telescope taken by ESA’s Gaia observatory on 18 February 2022.

Background frame: Cutout of the specially recorded image from Gaia’s sky mapper instrument at the first of the two observations from Gaia’s two telescopes. The reddish colour is artificial, chosen just for illustrative reasons. The frame shows a few relatively bright stars, several faint stars, a few disturbances – and a spacecraft. It is marked by the green circle.

Left grey inset: Zoom into the frame showing the Webb image at full resolution. It is the slightly extended speck of light in the centre. The other three bright dots are traces of energetic cosmic-ray particles which hit the CCD chip during the 2.5 seconds of exposure. The on-board software is capable of autonomously and reliably distinguishing these from star images.

Left grey inset: Zoom into the frame showing the Webb image at full resolution. It is the slightly extended speck of light in the centre. The other three bright dots are traces of energetic cosmic-ray particles which hit the CCD chip during the 2.5 seconds of exposure. The on-board software is capable of autonomously and reliably distinguishing these from star images.

Related article: Gaia snaps photo of Webb at L2 (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_snaps_photo_of_Webb_at_L2)

https://www.esa.int/ESA_Multimedia/Images/2022/03/Gaia_snaps_photo_of_Webb_zoom

ESA/Gaia/DPAC
Title: Re: ESA - Gaia updates
Post by: bolun on 03/24/2022 01:18 pm
Milky Way edge-on view

Basic structure of our home galaxy, edge-on view. The new results from ESA's Gaia mission provide for a reconstruction of the history of the Milky Way, in particular of the evolution of the so-called thick disc.

Related article: Gaia finds parts of the Milky Way much older than expected (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_finds_parts_of_the_Milky_Way_much_older_than_expected)

https://www.esa.int/ESA_Multimedia/Images/2022/03/Milky_Way_edge-on_view

Image credit: Stefan Payne-Wardenaar / MPIA
Title: Re: ESA - Gaia updates
Post by: bolun on 05/26/2022 04:38 pm
https://twitter.com/ESAGaia/status/1529493114108448769

Quote
We are proud to announce that the Shaw Prize in Astronomy 2022 has been awarded to Lennart Lindegren & Michael Perryman for their role in the conception & design of the @esa Hipparcos and #GaiaMission. Congratulations!

https://cosmos.esa.int/web/gaia/home
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/27/2022 09:08 am
This from the DR3 preview is fabulous:

https://twitter.com/ESAGaia/status/1528670075015806982

The amount of detail in that is incredible.

--- Tony
Title: Re: ESA - Gaia updates
Post by: deadman1204 on 05/27/2022 02:41 pm
Totally forgot that DR3 was happening this year!

Yay Gaia, the most under sung mission!
Title: Re: ESA - Gaia updates
Post by: Star One on 05/27/2022 03:31 pm
Isn’t DR3 supposed to include thousands of exoplanet discoveries?
Title: Re: ESA - Gaia updates
Post by: Star One on 05/27/2022 03:36 pm
CEPHEIDS AND THEIR RADIAL VELOCITY CURVES

The variable stars that nowadays are collectively called Cepheids are actually an ensemble of different types identifying three main groups: Classical Cepheids, type II Cepheids and anomalous Cepheids. Classical Cepheids are fundamental standard candles of the extragalactic distance scale. They are also important tracers of the young (~50-500 Myr) population in the host galaxy, while anomalous and type II Cepheids are believed to belong to the intermediate-age (few Gyr) and old (&gt;10 Gyr) populations, respectively.

Gaia Data Release 3 (Gaia DR3) will release multi-band light-curves for more than 15,000 Cepheids of all types in five different environments, namely, the Large and Small Magellanic Clouds, the Andromeda (M31) and Triangulum (M33) galaxies and the Milky Way (including its cluster population and its small satellite dwarf galaxies).

These pulsating stars have been confirmed and fully characterised by the Specific Object Study pipeline for Cepheids and RR Lyrae stars (called SOS Cep&amp;RRL, Clementini et al. 2016) developed by Coordination Unit 7 (CU7; variability processing) of the Gaia Data Processing and Analysis Consortium. Periods, amplitudes of the GBP, G and GRP light variations, and mean magnitudes computed as an intensity-average over the full pulsation cycle, will be published for these Cepheids, along with the parameters resulting from the Fourier decomposition of their G-band light curves (φ21, φ31, R21 and R31; see e.g. Clementini et al. 2016).

In addition, radial velocity time-series data will be released in Gaia DR3 for a subsample of about 800 Cepheids (see Ripepi et al. 2022, the paper describing the specific processing and validation of all-sky Cepheid variables released in Gaia DR3, for full details).

The light and radial velocity curves for a sample of classical Cepheids in the period range from ~7 to ~13 days are shown in Figure 1. The extraordinary precision of the Gaia data (uncertainties on the individual measurements are comparable with the symbol sizes) allows us to appreciate the “Hertzsprung Progression”, discovered about one century ago by the Danish astronomer E. Hertzsprung. This feature consists in the observation of a “bump” both in the light and radial velocity curves of classical Cepheids in the period range of 6 - 15 days, whose position moves from the descending to the rising branch of the light curve as the period increases. The “bump” is clearly discernible in the descending branch of the Cepheid BM Pup (P~7.2 days, top left in Figure 1); it moves backwards in phase becoming almost equivalent in magnitude to the main maximum for P~8.2 days, reaching the bottom of the ascending branch for V1364 Cyg (P~13 days, bottom right). The physical origin of the bump is not yet completely understood, however it is believed to be due to the resonance between the second overtone and the fundamental modes and it takes place when the period ratio between these two modes is close to 0.5.

The evolution of the bump phase as the period increases is observed and predicted from theoretical pulsation models to depend on the metallicity of the host galaxy. Indeed both models and observations point towards a longer period for the centre of the Hertzsprung Progression (the point where the bump reaches the same magnitude as the maximum light, immediately before it re-appears on the rising branch) as the metallicity of the host population decreases. Recent model predictions also suggest a dependence on the Helium abundance and the mass-luminosity relation. The position in period of the centre of the Hertzsprung Progression, accurately determined from Gaia light and radial velocity curves, can thus provide crucial constraints not only on the chemical composition of the observed classical Cepheids but also on the physics of intermediate mass stars.

 

References

Clementini et al. 2016: “Gaia Data Release 1. The Cepheid and RR Lyrae star pipeline and its application to the south ecliptic pole region”, A&amp;A, 595, A133
Ripepi et al. 2022: “Gaia DR3: Specific processing and validation of all-sky RR Lyrae and Cepheid stars - The Cepheid sample”, A&amp;A, submitted
 

Credits: ESA/Gaia/DPAC/CU7/CU6/CU5/INAF, Vincenzo Ripepi, Marcella Marconi, Roberto Molinaro, Silvio Leccia, Ilaria Musella (INAF-OACn Naples), Gisella Clementini, Alessia Garofalo (INAF-OAS Bologna), Laurent Eyer (University of Geneva) and the CU7/DPCG, CU5, and CU6 teams.

[Published: 27/05/2022]

https://www.cosmos.esa.int/web/gaia/iow_20220527
Title: Re: ESA - Gaia updates
Post by: ttle2 on 05/27/2022 06:02 pm
Isn’t DR3 supposed to include thousands of exoplanet discoveries?

No, that will be included in DR4.
Title: Re: ESA - Gaia updates
Post by: Star One on 05/27/2022 08:45 pm
Isn’t DR3 supposed to include thousands of exoplanet discoveries?

No, that will be included in DR4.
When’s that due, due to Covid I’ve lost track of the revised release schedule.
Title: Re: ESA - Gaia updates
Post by: Yiosie on 05/27/2022 10:57 pm
Isn’t DR3 supposed to include thousands of exoplanet discoveries?

No, that will be included in DR4.
When’s that due, due to Covid I’ve lost track of the revised release schedule.

NET 2025, according to this presentation from March (page 22):
https://cor.gsfc.nasa.gov/sigs/starssig/events/seminars/15-Mar-2022/2022.03.15_Gaia_Drimmel_Sildes.pdf
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/28/2022 07:22 am
Isn’t DR3 supposed to include thousands of exoplanet discoveries?

As others have said, that will be DR4 in ~2025.

They will be in a different part of the parameter space to most existing transit and RV discoveries - Gaia is most sensitive to Jupiter-like objects, in long (several year) orbits.

So it will be very useful data for estimating the abunance of systems like our own, which are very difficult to detect with current instruments.

--- Tony
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 05/28/2022 07:30 am
Gaia is a project I have been following since just before launch. In the run up to the launch they were saying that a new Data Release will come every year and it will include more and more stuff, which was detailed though in the DR schedule. After launch, and the delay did not have anything to do with it, they started started putting out more genetic statements like "time flies when you have lots of data". I don't know why the delay in the data releases compared to the pre-launch schedule came about: was it that they found more stars? Apparently early on there was an issue with reaching the faint end of the requirements, but at the press releases of DR1 they said that they found as many brighter stars as the original estimate for all stars, so likely that is not it. Did it take longer to create the algorithm pipelines because the Hipparcos pipeline could not be just adopted as they are and they required change? Was there a shortage of processing capacity on Earth due to say the inability to buy more processing power due to austerity cause by the Euro crisis? Honestly I wouldn't know if that is even true. I am guessing here, none of the Gaia people has ever come forward at least in public why they changed the release schedule beyond a generic "there was more data". What I can tell you though is that there was a likely political decision to release something every two years even if it is not complete. EDR3 came out two years ago because the whole DR3 was not ready. We are having the full DR3 here, which is what they released two years ago minus obvious errors found plus what per the original plan should have been released with DR3. Now we can guess that in 2024 the next release will come, whether it will be a DR4 or an EDR4, I don't know. The problem with this forum is also that while there are several people from the American scientific community who are in the know that are posting, we do not have that many Europeans to give us the inside scoop
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/28/2022 02:21 pm
Not quite sure why you're so unhappy, and please use paragraphs - that solid block of text is almost unreadable.

The reasons for delay are straight forward and pretty well known (covered by Space News amongst others).

First, there was around 9 months delay in the 1st release due to hardware problems, including the stray light issue. Aside from the stray light, the instruments are performing better at the bright end, so the catalogue now includes magnitudes to 3 rather than the original 5.7. There are also special techniques for even brighter stars, though the parallax errors are far greater. The faint end is where stray light affected things, so now the catalogue is to mag 20 rather than (from memory) the original 22**.

Second, complexity of processing was massively underestimated, taking about twice as much time to reduce the data. This is partly constrained my human resource and partly by compute. This reduced the frequency from the original anticipated annual release to at best once every two years. A small budget cut to DPRC hasn't helped with human resourcing either.

Third, DR3 was split due to the pandemic, which added 18 months to the full DR3 release date (13 June, very exciting!).

But the data quality far exceeds expectations and it has been revolutionary for galactic archaeology, and will be the basis for galactic research for decades (every astronomer I know routinely uses the data). And the quality and accuracy is still improving: DR3 will be about 20% better than DR2; DR4 should be at least the same better than DR3; and we'll get a bonus DR5 around 3 years after final end of mission (so ~2027).

Personally, DR4 is important because it includes the exoplanet list, which will massively increase the number of known cold Jupiters.

Anyway, it is a fabulous mission and the data quality is truly exceptional.

--- Tony

Edit: ** probably worth noting that the stray light issue affects crowded fields the most due to its affect on the PSF, so affects fewer stars than you'd think.
Title: Re: ESA - Gaia updates
Post by: Nomadd on 05/28/2022 05:59 pm
 Losing 2 magnitudes at the dim end is not a small loss.
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/29/2022 06:43 am
Losing 2 magnitudes at the dim end is not a small loss.

True, a full 2 magnitude loss would be a lot of stars.

The original goal for the astrometric measurements was ~20 (I remembered wrong; but note the "~"  ;D ). The biggest effect of the stray light was a loss of precision at faint magnitudes rather than not being able to observe the stars - about a 50% reduction in measurement accuracy.

And now the instruments are calibrated and all the mitigations in place, turns out the practical limit is 20.7, so a bit better than the original goal (I assume that ~20 mag was always a minimum expected performance so without those pesky sunshield fibres, it might have been even better).

The current performance data is here:

https://www.cosmos.esa.int/web/gaia/science-performance

--- Tony


Title: Re: ESA - Gaia updates
Post by: ttle2 on 05/29/2022 08:42 am
Losing 2 magnitudes at the dim end is not a small loss.

True, a full 2 magnitude loss would be a lot of stars.

The original goal for the astrometric measurements was ~20 (I remembered wrong; but note the "~"  ;D ). The biggest effect of the stray light was a loss of precision at faint magnitudes rather than not being able to observe the stars - about a 50% reduction in measurement accuracy.

And now the instruments are calibrated and all the mitigations in place, turns out the practical limit is 20.7, so a bit better than the original goal (I assume that ~20 mag was always a minimum expected performance so without those pesky sunshield fibres, it might have been even better).

The current performance data is here:

https://www.cosmos.esa.int/web/gaia/science-performance

--- Tony

I believe the faint magnitude limit isn't only (or even mainly) due to sensitivity, but the fact that the density of objects becomes too high (lots of quasars etc.) for Gaia to process. The current average completeness limit of 20.7 is a bit better than originally expected. Even now, the survey is deeper in less crowded fields.
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/29/2022 08:46 am
I believe the faint magnitude limit isn't only (or even mainly) due to sensitivity, but the fact that the density of objects becomes too high (lots of quasars etc.) for Gaia to process. The current average completeness limit of 20.7 is a bit better than originally expected. Even now, the survey is deeper in less crowded fields.

Agreed. In crowded fields, dilution due to the PSF is the limit, I think.

--- Tony
Title: Re: ESA - Gaia updates
Post by: ttle2 on 05/29/2022 08:51 am
I believe the faint magnitude limit isn't only (or even mainly) due to sensitivity, but the fact that the density of objects becomes too high (lots of quasars etc.) for Gaia to process. The current average completeness limit of 20.7 is a bit better than originally expected. Even now, the survey is deeper in less crowded fields.

Agreed. In crowded fields, dilution due to the PSF is the limit, I think.

--- Tony

There's also some hard limit for the number of objects (~1 million per square degree I think) that Gaia can track simultaneously, so it's not just optical confusion.
Title: Re: ESA - Gaia updates
Post by: Star One on 05/31/2022 08:35 am
Isn’t DR3 supposed to include thousands of exoplanet discoveries?

As others have said, that will be DR4 in ~2025.

They will be in a different part of the parameter space to most existing transit and RV discoveries - Gaia is most sensitive to Jupiter-like objects, in long (several year) orbits.

So it will be very useful data for estimating the abunance of systems like our own, which are very difficult to detect with current instruments.

--- Tony
Are they still estimating the discovery of at least 10,000 such exoplanets, which is the figure I saw quoted some years back now?
Title: Re: ESA - Gaia updates
Post by: jebbo on 05/31/2022 03:18 pm
Are they still estimating the discovery of at least 10,000 such exoplanets, which is the figure I saw quoted some years back now?

I haven't heard an update for ages. Last I heard was still >10,000 so certainly thousands. I'll see if I can find out.

--- Tony
Title: Re: ESA - Gaia updates
Post by: Hungry4info3 on 06/01/2022 10:20 am
~10,000 for the original five year mission. Many more (~70,000) for a ten year mission (which we've gotten), based on this tweet.
https://twitter.com/EricMamajek/status/1034696891248857089
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:48 am
Today's @ESAGaia data release also includes Solar System objects such as asteroids & planetary moons, and galaxies & quasars outside the Milky Way..

https://twitter.com/esa/status/1536242104514527233
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:50 am
Let’s have a look at the new spectacular sky maps in more detail. This map shows the speed at which stars move towards (bright areas) or away from us (dark areas). We can now see how the objects move over a large portion of the Milky Way’s disc.

https://twitter.com/esascience/status/1536260072325943296
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:50 am
Now let’s combine the map above (radial velocity) with the movement of stars across the sky (proper motion), showing the velocity of stars in three dimensions for 26 million stars.

https://twitter.com/esascience/status/1536260544990167041
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:51 am
Gaia also studies what is in between stars. This map shows the Milky Way interstellar dust..

https://twitter.com/esascience/status/1536261812907286528
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:52 am
This map shows a sample of Milky Way stars in #GaiaDR3. Redder stars are richer in metals. We see that some stars in our galaxy are made of primordial material, while others like our Sun are made of matter enriched by previous generations of stars..

https://twitter.com/esascience/status/1536262391830401024
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:53 am
In #GaiaDR3 @ESAGaia spotted starquakes that change the shapes of stars! They cause a star's surface to move while it rotates as shown in this animation. The frequency of the rotations and pulsations was increased to make them audible for humans.

https://twitter.com/esascience/status/1536272172255150081
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:54 am
Our @ESAGaia observatory has been mapping our galaxy since 2013, creating the most accurate and complete multi-dimensional map of the Milky Way. Today the third data set was released.

https://twitter.com/esa/status/1536275935288344577
Title: ESA - Gaia updates
Post by: Star One on 06/13/2022 10:55 am
Gaia data release 3: exploring our multidimensional Milky Way:

https://youtu.be/x6MGF0BhckE

Press release:

https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_sees_strange_stars_in_most_detailed_Milky_Way_survey_to_date
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:57 am
Ready for more.

@ESAGaia details?

#GaiaDR3 contains 813 thousand binary stars, the largest catalogue ever produced! This animation illustrates the sky-projected motions of binary stars whose orbits have been determined by the #GaiaMission..

https://twitter.com/esascience/status/1536300023331311617
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:57 am
The #GaiaSky 3.2.0 trailer, using #GaiaDR3 data!

https://twitter.com/GaiaSky_Dev/status/1536287312224690176
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 10:59 am
One result to highlight from our #GaiaDR3 chemical cartography paper: You want orbital actions? We've got orbital actions. And corresponding metallicity and [alpha/Fe]..

https://twitter.com/McMillan_Astro/status/1536291286344339456
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 11:00 am
#GaiaDR3: the "HR diagram" is henceforth called Cannon-Maury diagram, after Annie Jump Cannon and Antonia Maury, who first classified the relationship between stellar luminosity and colour.

https://twitter.com/TillSawala/status/1536290928897441793

Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 12:02 pm
Gaia has observed over 150K asteroids in our solar system

https://youtu.be/ypI-1v72-1I
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 02:04 pm
Missed our press briefing about today's@ESAGaia data release? #GaiaDR3..

https://twitter.com/esa/status/1536346050515980288
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/13/2022 02:09 pm
This ESA baby is giving you all that DR3 goodness..
 
@ESAGaia #DR3

https://twitter.com/DutchSpace/status/1536303718014103552
Title: Re: ESA - Gaia updates
Post by: deadman1204 on 06/13/2022 02:19 pm
Happy DR3 day!
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/14/2022 01:28 am
Hear Starquakes! Pulsating stars' frequency increased 8.6 million times

https://youtu.be/PrQ6ATHjQHs
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/14/2022 01:14 pm
Gaia mission measures metals in Milky Way stars

https://youtu.be/0UkV8OAWE9k
Title: Re: ESA - Gaia updates
Post by: Rondaz on 06/14/2022 06:58 pm
Treasure trove of Milky Way data in latest Gaia mission release

https://youtu.be/eGVN3U93faQ
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 06/25/2022 06:55 am
This is the main press release video, already shared above, but directly on Youtube:

https://www.youtube.com/watch?v=dk3SUMCYp5Q

In addition to the main event at ESA HQ, there were several national events. This is the overview page:

https://www.cosmos.esa.int/web/gaia/dr3-events

Frustratingly, since I am a Greek, there was no Greek Gaia DR3 event. Croatia had one, Slovenia had one (and both are smaller than Greece, hence mentioned) but the National Observatory failed its Greek taxpayers, such as me. Thankfully the UK Space Agency and the British Gaia consortium did organize an event lasting over two hours and put it here:

https://www.youtube.com/watch?v=rjCaRSJMIhc

The event begins a bit after the 10 minute mark, includes the first 15 minutes from the main ESA event, explains the datasets much better than the main event. Also the image quality of the video is bad plus several times the speakers are too far away from the microphone to actually listen to them. It is very worth watching though.
Title: Re: ESA - Gaia updates
Post by: eeergo on 06/27/2022 01:35 pm
Great view, for reference when discussing asteroid missions, of the asteroid population in the Solar System as can be detected by Gaia (taking into account a large part of the population of asteroids which spend at least part of their orbits at <1AU will be missing because of Gaia's observation directions), with very well defined Trojan populations at Sun-Jupiter's L4, L5 and even L3.

https://twitter.com/ESAGaia/status/1541413043250364417
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 08/24/2022 09:14 pm
For some reason the front page article about Gaia does not appear on this thread:

https://www.nasaspaceflight.com/2022/08/gaia-reveals-sun-evolution/
Title: Re: ESA - Gaia updates
Post by: jebbo on 08/31/2022 08:55 am
A thread on a very nice new product from DR3: a line-of-sight extinction map.

https://twitter.com/ESAGaia/status/1564891644964610048

Edit: and the web page https://www.cosmos.esa.int/web/gaia/dr3-what-is-in-between-the-stars
--- Tony
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 09/23/2022 07:14 am
A protogalaxy in the Milky Way may be our galaxy’s original nucleus

https://www.sciencenews.org/article/milky-way-galaxy-nucleus-oldest-stars-protogalaxy

After Gaia Enceladus, also nicknamed The Sausage which merge with the Milky Way billions of years ago and an even earlier merger, now we have the stars that formed the Milky Way before all these collisions. In terms of galactic archaeology Gaia has been revolutionary.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/25/2022 04:41 am
The Gaia team announced a Focused Product Released, #GaiaFPR is the hashtag, that will include six products. This is a limited early release from Gaia DR4 which is not due before the end of 2025. Here is a tweet starting the announcement thread:

https://twitter.com/ESAGaia/status/1574737051500810241

For those that do not want to click through I have copied the list from thread. This is based on 66 months of observations.

(1) updated astrometry for Gaia's Solar System objects
(2) Astrometry and photometry from engineering images taken in selected regions of high source density (only Omega Cen for this FPR)
(3) The first results of quasars' environment analysis for gravitational lenses search
(4) Extended radial velocity epoch data for Long Period Variables
(5) Pre-main sequence accretion parameters
(6) Diffuse Interstellar Bands from aggregated RVS spectra
Title: Re: ESA - Gaia updates
Post by: eeergo on 11/04/2022 09:16 am
Closest black hole to Earth found by Gaia (Gaia BH1):

https://twitter.com/ESAGaia/status/1588474741999878145
Title: ESA - Gaia updates
Post by: Star One on 11/30/2022 04:21 pm
Discovery and description of two young open clusters in the primordial group of NGC 6871

A primordial group of open clusters containing NGC 6871 is confirmed and described through Gaia DR3 data and the previous literature. It is a star-forming complex containing at least six young OCs, including Teutsch 8, FSR 198 and Biurakan 2. Two nearby OCs (Casado 82 and Casado-Hendy 1) are newly identified and studied in detail and found to be also members of the cited group. The parameters of the components are sufficiently similar to postulate the case of at least six clusters born from a single GMC. None of the cluster pairs of the group seems to be an authentic binary cluster, with the possible exception of the candidate pair Teutsch 8/FSR 198. Instead, NGC 6871 seems to be disintegrating, and the primordial group members appear to be dispersing out rapidly. Searching for new open clusters in the vicinity of young or grouped OCs using Gaia data is an efficient strategy to find new associated OCs forming primordial groups.

https://arxiv.org/abs/2211.12843
Title: Re: ESA - Gaia updates
Post by: Star One on 12/19/2022 03:35 pm
The Milky Way’s plane of satellites is consistent with ΛCDM

Abstract
The Milky Way is surrounded by 11 ‘classical’ satellite galaxies in a remarkable configuration: a thin plane that is possibly rotationally supported. Such a structure is thought to be highly unlikely to arise in the standard (ΛCDM) cosmological model (Λ cold dark matter model, where Λ is the cosmological constant). While other apparent discrepancies between predictions and observations of Milky Way satellite galaxies may be explained either through baryonic effects or by invoking alternative forms of dark matter particles, there is no known mechanism for making rotating satellite planes within the dispersion-supported dark matter haloes predicted to surround galaxies such as the Milky Way. This is the so-called ‘plane of satellites problem’, which challenges not only the ΛCDM model but the entire concept of dark matter. Here we show that the reportedly exceptional anisotropy of the Milky Way satellites is explained, in large part, by their lopsided radial distribution combined with the temporary conjunction of the two most distant satellites, Leo I and Leo II. Using Gaia proper motions, we show that the orbital pole alignment is much more common than previously reported, and reveal the plane of satellites to be transient rather than rotationally supported. Comparing with new simulations, where such short-lived planes are common, we find the Milky Way satellites to be compatible with standard model expectations.

https://www.nature.com/articles/s41550-022-01856-z
Title: Re: ESA - Gaia updates
Post by: Star One on 12/20/2022 02:57 pm
The Poor Old Heart of the Milky Way

Abstract
Our Milky Way should host an ancient, metal-poor, and centrally concentrated stellar population, which reflects the star formation and enrichment in the few most massive progenitors that coalesced at high redshift to form the proto-Galaxy. While metal-poor stars are known to reside in the inner few kiloparsecs of our Galaxy, current data do not yet provide a comprehensive picture of such a metal-poor "heart" of the Milky Way. We use information from Gaia Data Release 3, especially the XP spectra, to construct a sample of 2 million bright (GBP &lt; 15.5 mag) giant stars within 30° of the Galactic center (GC) with robust [M/H] estimates, δ[M/H]  0.1. For ∼1.25 million stars we calculate orbits from Gaia Radial Velocity Spectrometer velocities and astrometry. This sample reveals an extensive, ancient, and metal-poor population that includes ∼18,000 stars with −2.7 &lt; [M/H] &lt; −1.5, representing a stellar mass of 5 × 107 M. The spatial distribution of these [M/H] &lt; −1.5 stars has a Gaussian extent of only ${\sigma }_{{{R}}_{{\rm{GC}}}}\sim 2.7\,\mathrm{kpc}$ around the GC, with most orbits confined to the inner Galaxy. At high orbital eccentricities, there is clear evidence for accreted halo stars in their pericentral orbit phase. Most stars show [α/Fe] enhancement and [Al/Fe]–[Mn/Fe] abundances expected for an origin in the more massive portions of the proto-Galaxy. Stars with [M/H] &lt; −2 show no net rotation, whereas those with [M/H] ∼ −1 are rotation dominated. These central, metal-poor stars most likely predate the oldest disk population (τage ≈ 12.5 Gyr), which implies that they formed at z  5, forging the proto-Milky Way.

https://iopscience.iop.org/article/10.3847/1538-4357/ac9e01

Long form explanation of their methodology with the Gaia data.

https://phys.org/news/2022-12-astronomers-ancient-heart-milky-galaxy.html
Title: Re: ESA - Gaia updates
Post by: Mongo62 on 12/20/2022 07:03 pm
The Milky Way’s plane of satellites is consistent with ΛCDM

Abstract
The Milky Way is surrounded by 11 ‘classical’ satellite galaxies in a remarkable configuration: a thin plane that is possibly rotationally supported. Such a structure is thought to be highly unlikely to arise in the standard (ΛCDM) cosmological model (Λ cold dark matter model, where Λ is the cosmological constant). While other apparent discrepancies between predictions and observations of Milky Way satellite galaxies may be explained either through baryonic effects or by invoking alternative forms of dark matter particles, there is no known mechanism for making rotating satellite planes within the dispersion-supported dark matter haloes predicted to surround galaxies such as the Milky Way. This is the so-called ‘plane of satellites problem’, which challenges not only the ΛCDM model but the entire concept of dark matter. Here we show that the reportedly exceptional anisotropy of the Milky Way satellites is explained, in large part, by their lopsided radial distribution combined with the temporary conjunction of the two most distant satellites, Leo I and Leo II. Using Gaia proper motions, we show that the orbital pole alignment is much more common than previously reported, and reveal the plane of satellites to be transient rather than rotationally supported. Comparing with new simulations, where such short-lived planes are common, we find the Milky Way satellites to be compatible with standard model expectations.

https://www.nature.com/articles/s41550-022-01856-z

In other words, a lot of special pleading to mak Lambda-CDM work.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/14/2023 07:03 am
This is a post I have wanted to do for a few months now, since the DR3 papers got published on the cosmos esa website (https://www.cosmos.esa.int/web/gaia/dr3-papers). This is mostly about the solar system object  survey though I will also mention a bit about quasar/galaxies and stars. My first idea for this post came when I read the documentation (https://gea.esac.esa.int/archive/documentation/GDR3/index.html) but now that the papers are mostly out I can improve.

First of all Gaia processing works by having an input catalog for the part of the sky they are processing (usually what the scanned in a day), matching with what Gaia actually saw and then treating what was not matched. For Gaia DR1 what they had as a base was the Tycho star catalog from Hipparcos plus a star catalog they created from two observatories, one in the northern and one in the southern hemisphere. The reason it is only a star catalog is that just learning how to handle, let alone treat the data. For DR2 they input the DR1 catalog as the scanning input for the star catalog. For quasars they used external catalogs of quasar that they matched and did some limited QA in DR2. In solar system objects they had a predetermined catalog from across the solar system and tested how well they could match with real data. We must remember that first and foremost Gaia is a star mapping mission so the rest of the products are bonuses, they know that they miss stuff because they optimize for completeness of stars.

In Gaia DR3 they followed again the match the external catalog first, improve data and then build upon similarly with new objects. For quasars and galaxies they created two pairs of catalogs: one pair is going for purity of sample and the other for completeness. Now there are internal quality controls on the spacecraft in order send down only good data which mean that the Gaia Galaxy catalog misses a lot of barred galaxies because the QA software on the spacecraft rejects the image and does not send it down because it reads the bars as cosmic rays that it does not want to download. When they validate the catalogs with other mission data, it turns out Hubble simply has not done a systematic survey of galaxies and quasars, which limits validation. When validating with Earth based surveys they see the effects of the atmosphere, or in astronomer speak "seeing" conditions of the observatories. Still the data is valuable even if biased and will be the validation survey for future space based surveys

Thus now I get to solar system objects. DR3 used data collected over a 34 month period, 25 July 2014 to 28 May 2017. An object is identified over Gaia's CCDs when it transits over them as the spacecraft rotates around itself and around the sun at Sun Earth L2. A solar system object is tagged when it transits over the sensor in particular orbit that shows that it moves as opposed to being a fixed star or an even more fixed galaxy or quasar. Now the processing is not capable of recognizing yet all possible ways a solar system object can transit its field of view plus it is better at seeing objects that move more across the scan line as opposed to vertically down scan lines. In other words, it will not catch everything. Still it caught quite a few object transits. Figure 1 is where they are in the sky

For that matter they did not use all the transits in that period data, there are too many so they rejected from further process a transit that was too close to a bright star or other SSO and objects that did not transit at least 8 times in these 34 months. As mentioned above the way Gaia processing works is that they need an input catalog at the start of processing and for this purpose they downloaded from the Minor Planet Center all numbered objects data as of December 13 2017 and put them in the sky as they should be per the ephemerid so as to match them with the downloaded data. The input selection had  3,513,248 transits for 156,837 known asteroids. For the last six months, from December 1st 2016, they did not reject all unknown object transits but kept them and thus identified previously unknown objects. In other words, the new SSOs in DR3 are only those from the last 6 months. Still, this is what they found:

Table 2: Object types in DR3.
Object type number of objects
Atira 1
Aten 43
Apollo 230
Amor 173
Mars Crossers 1550
Inner Main Belt 3305
Main Belt 144,975
Outer Main Belt 4940
Jupiter Trojans 1550
Centaurs 8
TNOs 24
Others 2
Total asteroids 156,801
Unmatched moving objects 1,320
Planetary satellites 31
Total 158,152

Notice that no comets were identified. For the 1320 unmatched objects in February 2022 they downloaded the latest data from the Minor Planet Center and divided the sky into tiles to match any unmatched data. They identifies 712 of these object belonging to 567 different asteroids (several crossed twice). The other 608 are new objects and their data was put in the MPC database as such, along with the identified.

The paper afterwards turns mostly to QA/QC. First they compared the orbits they calculated from the 34 months with what is in the MPC from a much larger timeframe. Figure 10 is the residuals dispersion. The brighter the object the less the error and take note that JPL MPC data is not perfect, so some objects Gaia-only data had fewer errors.

They then tried to see how well it worked with identifying binary asteroids using 4337 Arecibo, which is well known and they know where in each transit they saw each component and it was not so great. Thus they think they cannot find automatically binaries from processing the transit. 21 Lutecia was used to see if there is a difference between the computer photocenter and the center of mass and they found that there is room for improvement. Pluto - Charon were used as a flag to see if the could resolve them from the transits and generally they were happy. Next up they tried to see if they could use Gaia data with other data in JPL ephemerides to see if they could calculate the Yarkovsky effect using visual only, no radar data. Using the example 3200 Phaethon they found something within 1σ of the JPL data from radar which is good. Then they did the same for 1620 Geographos for which there is no radar data. The scientific community can now work with the rest of the Gaia data

Next up they compared photometry with existing data. Photometry worked best for NEOs which are see from all sorts of phase angles, as opposed to other things in the solar system that are only seen from a limited number of angles. They then inversed the photometry to calculate object shape using a simplified elliptical asteroid model using DAMIT models as ground truth. They limited their analysis for the first thousand numbered asteroids, being the brightest, and only those for which they had at least 30 good transits. That meant 430 asteroids. They obtained the right rotation period P for 229 of them and for many of the rest they got a 2P period instead of P which is something reasonable because of how inversion works. Honestly for me personally, this looks like a good output. They also compared photometry with 21 Lutetia and 2867 Steins that were visited by Rosetta. For Lutetia for which only one side was imaged several of the transits were of the unimaged side and some of the errors, which were small, can be attributed to the model not being perfect for the unimaged part. On Steins error was very small.

Honestly I see real work there. There is a lot of data there for other scientists to play with and deduce new information. Also I understand why the Gaia focused product release, as the early release of DR4 is called which is coming out later this year based on 66 months of data will include solar system objects, as opposed to waiting for full DR4 in the end of 2025: They are now happy with the solar system object processing chain and will work now with more data, including unknown SSOs from the start instead of only 6 months data. Still let us not forget that Gaia is not pointed too close to the sun which means in turn that it is harder to find SSOs closer to the sun than earth. Also Gaia identification of objects starts dropping around magnitude 17 especially in crowded parts of the sky, meaning that TNO numbers will be limited
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 01/27/2023 05:51 am
Meet your neighbours: CNS5 - the fifth catalogue of nearby stars

 https://www.cosmos.esa.int/web/gaia/iow_20230125

This also includes a video at the bottom:

https://www.youtube.com/watch?v=MuWtZE3klj0

Per the revised catalog, 70% of which is based on Gaia, within 25 parsecs or 81 light years there are 5931 objects, including 5230 stars and 701 brown dwarfs. Also two thirds of actual brown dwarfs within these 25 parsecs are believed to be undiscovered - too faint to properly measure parallax yet.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 02/08/2023 05:19 am
Gaia's living and breathing Milky Way

https://www.youtube.com/watch?v=bVb70e5BLW8

This is very interesting in its own right though it has a technical issue the first two minutes. What I also want to point out is something buried in the end: Gaia is expected to run out of cold gas for its thrusters between January and March 2025
Title: Re: ESA - Gaia updates
Post by: deadman1204 on 02/17/2023 12:16 am
Gaia's living and breathing Milky Way

https://www.youtube.com/watch?v=bVb70e5BLW8

This is very interesting in its own right though it has a technical issue the first two minutes. What I also want to point out is something buried in the end: Gaia is expected to run out of cold gas for its thrusters between January and March 2025
Its easy to forget that they have only analyzed the first 34 months of data! They expect DR5 (final) one in 2030
Title: Re: ESA - Gaia updates
Post by: bolun on 05/02/2023 07:45 pm
Gaia discovers a new family of black holes (https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_discovers_a_new_family_of_black_holes)

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Using data from ESA’s Gaia mission, astronomers have discovered not only the closest but also the second closest black hole to Earth. The black holes, Gaia BH1 and Gaia BH2, are respectively located just 1560 light-years away from us in the direction of the constellation Ophiuchus and 3800 light-years away in the constellation Centaurus. In galactic terms, these black holes reside in our cosmic backyard.

The two black holes were discovered by studying the movement of their companion stars. A strange ‘wobble’ in the movement of the stars on the sky indicated that they are orbiting a very massive object. In both cases, the objects are approximately ten times more massive than our Sun. Other explanations for these massive companions, like double-star systems, were ruled out since they do not seem to emit any light.

Image credit: ESA/Gaia/DPAC
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 09/24/2023 05:58 am
We are three weeks away from GaiaFPR, which is a preview of DR4. There was a series of sessions at the European Astronomical Society meeting in Krakow about Gaia and some presentations have been posted here:

https://great.ast.cam.ac.uk/Greatwiki/GreatMeet-PM16

A few standouts:

For Ω Centauri GaiaDr3 has something like 50,000 stars. The FPR will have over half a million new sources with those in DR3 purposely excluded. This is a test of the new full frame method for crowded regions. When the scan line saturated from too many stars, the spacecraft was programmed to simply take a picture of the whole frame. In the earlier data releases they had not process the whole sky images. For Focused Product Release they are showing the results of their new processing chain starting with Ω Cen

FPR actually has fewer solar system objects than DR3. However they have improved their processing chain, used the 66 months and thus have superior quality of observations. DR4 will have 350,000 objects as opposed to the 156,000 objects in FPR and 158,000 objects in DR3

GaiaNIR, the successor, will not be launched until 20 years after the end of Gaia on purpose: they want the astrometric baseline. So even if everything is funded and developed on time, I would guess it would wait on the ground for its time.

DR4 will be the largest astronomic catalog ever and it will surpass the Hubble Fine Guidance Sensor catalog which I think currently has the crown. Nothing is said about DR5, but I would assume that after the spacecraft dies a new full reprocessing of the data will have with all Gaia data. DR4 is for 66 months which is the original mission plan but the spacecraft is still alive and gathering data.
Title: Re: ESA - Gaia updates
Post by: Star One on 10/11/2023 08:30 am
New Gaia release reveals rare lenses, cluster cores and unforeseen science

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Today, ESA's Gaia mission releases a goldmine of knowledge about our galaxy and beyond. Among other findings, the star surveyor surpasses its planned potential to reveal half a million new and faint stars in a massive cluster, identify over 380 possible cosmic lenses, and pinpoint the positions of more than 150 000 asteroids within the Solar System.

https://www.esa.int/Science_Exploration/Space_Science/Gaia/New_Gaia_release_reveals_rare_lenses_cluster_cores_and_unforeseen_science

All the papers are linked to in the press release above.
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 10/12/2023 05:17 am
There was a press conference that came with this release. It was partially recorded and put here:

https://www.youtube.com/watch?v=_TcGLJz0FUQ

The first session that apparently was from Timo Prusti that gave a general overview was not recorded, it starts midway in the second about Omega Centauri. In DR3 at the center of Ω Centauri there is a hole. Using the engineering camera they set up a new methodology and now have half a million plus stars there on high resolution. It is not as good as the normal process for reasons they explain but it is better than the current hole. They also mention that they will follow the same technique for another 8 crowded areas of the sky. I do have a question that was not asked or answered (there was no Q&A session): I know that for the next Data Release they use the previous release as the ingestion catalog. Are these new stars going to be in the ingestion catalog for DR4? My guess would be no because while for Ω Centauri the data is out now 2 years before DR4, that may not be true for the other 8 regions. I guess we need to wait for DR5

Interstellar Dust (I could be getting the order of the presentations wrong). They used the spectra of the stars that are far from the dusty galactic plain as pure endmembers and using the same stellar classes they mapped something like 2,000,000 voxels of the Milky Way for dust. They also put extracted some new information about the diffuse interstellar bands but no actual solution as to what molecules cause them. They did show some 2D visualizations, the 3D one at the end did not work. You could see though the spiral arms of the galaxy, or at least I thought I did

Pulsating Stars: They started from the over a billion stars of the Gaia catalog and after several quality selections they ended up with some 10,000 pure samples that are binaries. The pulsation is due to the rotation and how it effects both the other star and the gas and dust between them. New stellar astrophysics information came out of this analysis

Gravitational Lenses: Gaia was never planned for this task, it emerged from the science community using its data. They begin with the quasar catalog of DR3 which is the largest quasar catalog and search for nearby objects. 87% of quasars are lonely, but the rest have nearby companions, including 100,000 objects that are not in DR3 (quality flags?). They they used classification with known doublets and quadruplets to find something similar in the 500,000 nearby objects, which is too many to do by hand. The 381 objects may not seem much, but for quadruplet it is something like 60% more that are known and for doublets 130% more (I write from memory, I can be wrong). Now they have applied at giant earth based telescopes for spectroscopic measurements of these 381 because they are mostly too faint for Gaia spectroscopy. We will see how many get confirmed

The last presentation was about the asteroids. As a mentioned in an earlier post they are fewer objects than in DR3. However because they have now 66 months of observation they are 2 orders of magnitude or in layman's terms 100 times better in terms of accuracy than DR3 for the main asteroid belt. You see 66 months is good enough to have seen whole orbits for the main belt leading that better accuracy. For Jupiter Trojans though they do not have a full orbit so it si only 2 to 5 times more accurate than DR3. They also wet our appetites for DR4. They will have far more objects including for the first time comets near their perihelion. They compared their orbital parameters with the JPL catalog as validation, the JPL catalog has far more years of observation than Gaia. For the first 50,000 numbered objects orbit difference is on the average 1 km (yes, that good) and the spread looked quite random and tight on the chart. They mentioned how they had 42 million observation which they same submitted to the Minor Planet Center which has under 200 million observations of minor planets overall since Ceres discovery on January 1 1801.

If you have the time, it is worth watching
Title: Re: ESA - Gaia updates
Post by: FutureSpaceTourist on 12/19/2023 08:03 am
https://twitter.com/esascience/status/1737033914537885892

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🥳🎂 @ESAGaia celebrates its tenth anniversary since launch🚀
👇Let’s look at the #GaiaMission in numbers

Quote
2/ What have we learned about our galaxy in this decade of research?

⚖️ how to weigh our galaxy
🌀 what our galaxy looks like
💥 which collisions took place with other dwarf galaxies

Find out more 👉 https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_s_decade_of_discoveries_unravelling_the_intricacies_of_our_galaxy

https://twitter.com/esascience/status/1737033923404689596

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3. Have a look around our Milky Way in this high-resolution interactive image by @ESAGaia
👉 https://www.esa.int/ESA_Multimedia/Images/2020/12/Interactive_map_of_the_sky_from_Gaia_s_Early_Data_Release_3
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 12/20/2023 05:12 am
ESA had three press releases today about the 10 year launch anniversary of Gaia

https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_s_decade_of_discoveries_unravelling_the_intricacies_of_our_galaxy

Mostly a write up of what is on the previous post

https://www.esa.int/ESA_Multimedia/Images/2023/12/Gaia_s_10th_anniversary

The post above in summary

https://www.esa.int/ESA_Multimedia/Videos/2023/12/Galactic_Chloe_-_the_Gaia_mission

Galactic Chloe is apparently a Swiss I would guess social media influencer - science popularizer. 12 minute video in English
Title: Re: ESA - Gaia updates
Post by: AegeanBlue on 03/19/2024 10:24 pm
New quasar catalog from Gaia. This is the ESA press release

https://www.esa.int/ESA_Multimedia/Images/2024/03/Gaia_maps_largest_ever_collection_of_quasars_in_space_and_time

Also there is article on Universetoday. I think the name of the catalog is Quaia