Author Topic: ESA - Gaia updates  (Read 54237 times)

Offline grondilu

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ESA - Gaia updates
« 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.

Space is pretty much literally an astronomically-high hanging fruit.

Offline bolun

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Re: ESA - Gaia updates
« Reply #1 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
« Last Edit: 02/06/2014 01:23 PM by bolun »

Offline bolun

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Re: ESA - Gaia updates
« Reply #2 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #3 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/

Offline Star One

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ESA - Gaia updates
« Reply #4 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.
« Last Edit: 02/13/2014 03:58 PM by Star One »

Offline jebbo

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Re: ESA - Gaia updates
« Reply #5 on: 02/17/2014 08:24 AM »
Images of Gaia at L2 from the VST at Paranal

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

« Last Edit: 02/17/2014 08:24 AM by jebbo »

Offline bolun

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Re: ESA - Gaia updates
« Reply #6 on: 03/05/2014 11:11 AM »

Offline jebbo

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Re: ESA - Gaia updates
« Reply #7 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.

Offline jebbo

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Re: ESA - Gaia updates
« Reply #8 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

Offline baldusi

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Re: ESA - Gaia updates
« Reply #9 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?

Offline as58

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Re: ESA - Gaia updates
« Reply #10 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...

Offline baldusi

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Re: ESA - Gaia updates
« Reply #11 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?

Offline ngc3314

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Re: ESA - Gaia updates
« Reply #12 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).

Offline baldusi

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Re: ESA - Gaia updates
« Reply #13 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.

Offline ngc3314

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Re: ESA - Gaia updates
« Reply #14 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.

Offline bolun

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Re: ESA - Gaia updates
« Reply #15 on: 06/10/2014 08:46 PM »

Offline bolun

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Re: ESA - Gaia updates
« Reply #16 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.

Offline gosnold

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Re: ESA - Gaia updates
« Reply #17 on: 06/16/2014 06:47 PM »
That's a lot of unexpected problems, though the science impact seems limited.

Offline gosnold

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Re: ESA - Gaia updates
« Reply #18 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/), 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.
« Last Edit: 06/25/2014 06:51 PM by gosnold »

Offline Star One

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Re: ESA - Gaia updates
« Reply #19 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?

Offline denis

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Re: ESA - Gaia updates
« Reply #20 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/), 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 ;)

Offline gosnold

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Re: ESA - Gaia updates
« Reply #21 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.

« Last Edit: 06/26/2014 07:58 PM by gosnold »

Offline denis

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Re: ESA - Gaia updates
« Reply #22 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!

Offline as58

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Re: ESA - Gaia updates
« Reply #23 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?

Offline bolun

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Re: ESA - Gaia updates
« Reply #24 on: 07/05/2014 04:20 PM »

Offline gosnold

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Re: ESA - Gaia updates
« Reply #25 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #26 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #27 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.

Offline denis

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Re: ESA - Gaia updates
« Reply #28 on: 07/29/2014 09:50 PM »

More detailed report on:

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.

Offline Lewis007

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Re: ESA - Gaia updates
« Reply #29 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #30 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

Offline Semmel

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Re: ESA - Gaia updates
« Reply #31 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.

Offline denis

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Re: ESA - Gaia updates
« Reply #32 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.
« Last Edit: 09/22/2014 08:08 PM by denis »

Offline Semmel

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Re: ESA - Gaia updates
« Reply #33 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!

Offline denis

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Re: ESA - Gaia updates
« Reply #34 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).

Offline denis

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Re: ESA - Gaia updates
« Reply #35 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


credits: ESA/Gaia/DPAC/UB/IEEC
« Last Edit: 11/16/2014 01:32 AM by denis »

Offline bolun

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Re: ESA - Gaia updates
« Reply #36 on: 01/19/2015 08:39 PM »

Offline Star One

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Re: ESA - Gaia updates
« Reply #37 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.

Offline bolun

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Re: ESA - Gaia updates
« Reply #38 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #39 on: 08/26/2015 09:12 AM »

Offline Star One

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Re: ESA - Gaia updates
« Reply #40 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.

Offline denis

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Re: ESA - Gaia updates
« Reply #41 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).


Offline philw1776

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Re: ESA - Gaia updates
« Reply #42 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?
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline denis

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Re: ESA - Gaia updates
« Reply #43 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.
...

Offline Star One

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Re: ESA - Gaia updates
« Reply #44 on: 08/28/2015 08:12 PM »
Thanks for that link. So no exo-planet list until 2022.

Offline denis

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Re: ESA - Gaia updates
« Reply #45 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)

Offline Burninate

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Re: ESA - Gaia updates
« Reply #46 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
« Last Edit: 08/28/2015 11:53 PM by Burninate »

Offline bolun

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Re: ESA - Gaia updates
« Reply #47 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/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

Offline philw1776

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Re: ESA - Gaia updates
« Reply #48 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?
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline as58

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Re: ESA - Gaia updates
« Reply #49 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)

Offline bolun

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Re: ESA - Gaia updates
« Reply #50 on: 06/29/2016 10:33 AM »

Offline as58

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Re: ESA - Gaia updates
« Reply #51 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/
« Last Edit: 07/04/2016 09:45 AM by as58 »

Offline Star One

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ESA - Gaia updates
« Reply #52 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
« Last Edit: 07/29/2016 07:06 PM by Star One »

Online hop

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Re: ESA - Gaia updates
« Reply #53 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
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.
« Last Edit: 08/02/2016 05:25 AM by hop »

Offline redliox

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Re: ESA - Gaia updates
« Reply #54 on: 08/02/2016 05:18 AM »
Gaia isn't malfunctioning thermally is it?
"Let the trails lead where they may, I will follow."
-Tigatron

Online hop

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Re: ESA - Gaia updates
« Reply #55 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...

Offline as58

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Re: ESA - Gaia updates
« Reply #56 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.

Offline baldusi

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Re: ESA - Gaia updates
« Reply #57 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.

Offline jebbo

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Re: ESA - Gaia updates
« Reply #58 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

Offline Nomadd

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Re: ESA - Gaia updates
« Reply #59 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.
« Last Edit: 08/17/2016 04:40 PM by Nomadd »

Offline jacqmans

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Re: ESA - Gaia updates
« Reply #60 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 Cañada, 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.

Offline denis

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Re: ESA - Gaia updates
« Reply #61 on: 09/02/2016 07:59 PM »
Information and statistics on the first data release:

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/


Image credit: ESA/Gaia/DPAC.
« Last Edit: 09/02/2016 08:10 PM by denis »

Offline zubenelgenubi

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Re: ESA - Gaia updates
« Reply #62 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!
« Last Edit: 09/02/2016 11:30 PM by zubenelgenubi »
Support your local planetarium!

Offline Nilof

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Re: ESA - Gaia updates
« Reply #63 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?
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline JulesVerneATV

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Re: ESA - Gaia updates
« Reply #64 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #65 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.



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
« Last Edit: 09/12/2016 02:22 PM by bolun »

Offline bolun

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Re: ESA - Gaia updates
« Reply #66 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

Offline as58

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Re: ESA - Gaia updates
« Reply #67 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #68 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. Sagristà 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 Cañada, 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #69 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

Offline jgoldader

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Re: ESA - Gaia updates
« Reply #70 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.
Recovering astronomer

Offline denis

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Re: ESA - Gaia updates
« Reply #71 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

Offline Mongo62

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Re: ESA - Gaia updates
« Reply #72 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

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.

Offline Galactic Penguin SST

Re: ESA - Gaia updates
« Reply #73 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?)
Chinese spaceflight is a cosmic riddle wrapped in a galactic mystery inside an orbital enigma... - (not) Winston Churchill

Offline CuddlyRocket

Re: ESA - Gaia updates
« Reply #74 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, 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.

Offline Stan-1967

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Re: ESA - Gaia updates
« Reply #75 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, 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #76 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, 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.

Offline as58

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Re: ESA - Gaia updates
« Reply #77 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.
« Last Edit: 09/15/2016 10:04 AM by as58 »

Offline Star One

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Re: ESA - Gaia updates
« Reply #78 on: 09/15/2016 07:55 AM »
Are systematic errors those errors introduced into the results by Gaia itself?

Offline as58

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Re: ESA - Gaia updates
« Reply #79 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 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).

Offline Star One

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Re: ESA - Gaia updates
« Reply #80 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 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.

Offline as58

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Re: ESA - Gaia updates
« Reply #81 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #82 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #83 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

Offline as58

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Re: ESA - Gaia updates
« Reply #84 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.

Online Bubbinski

Re: ESA - Gaia updates
« Reply #85 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?
« Last Edit: 09/15/2016 07:31 PM by Bubbinski »
I'll even excitedly look forward to "flags and footprints" and suborbital missions. Just fly...somewhere.

Offline Star One

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ESA - Gaia updates
« Reply #86 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.
« Last Edit: 09/15/2016 07:57 PM by Star One »

Offline denis

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Re: ESA - Gaia updates
« Reply #87 on: 09/15/2016 08:41 PM »
Congratulations to the Gaia craft and team!
Thanks !  :P

Offline Hungry4info3

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Re: ESA - Gaia updates
« Reply #88 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).

Offline Star One

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ESA - Gaia updates
« Reply #89 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
« Last Edit: 09/20/2016 06:58 AM by Star One »

Offline denis

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Re: ESA - Gaia updates
« Reply #90 on: 09/26/2016 07:50 PM »
There is a search page, 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.

« Last Edit: 09/26/2016 07:51 PM by denis »

Offline Star One

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Re: ESA - Gaia updates
« Reply #91 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

Offline jgoldader

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Re: ESA - Gaia updates
« Reply #92 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.
Recovering astronomer

Offline bolun

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Re: ESA - Gaia updates
« Reply #93 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/

Offline Star One

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Re: ESA - Gaia updates
« Reply #94 on: 11/22/2016 08:19 PM »

Offline bolun

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Re: ESA - Gaia updates
« Reply #95 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/

Offline as58

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Re: ESA - Gaia updates
« Reply #96 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

Offline denis

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Re: ESA - Gaia updates
« Reply #97 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 ?

Offline as58

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Re: ESA - Gaia updates
« Reply #98 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.

Offline jebbo

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Re: ESA - Gaia updates
« Reply #99 on: 02/09/2017 11:38 AM »

Offline Star One

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Re: ESA - Gaia updates
« Reply #100 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/

Offline Star One

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Re: ESA - Gaia updates
« Reply #101 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #102 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/


Offline bolun

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Re: ESA - Gaia updates
« Reply #103 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


Offline Ben the Space Brit

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Re: ESA - Gaia updates
« Reply #104 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!
"Oops! I left the silly thing in reverse!" - Duck Dodgers

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The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline Star One

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ESA - Gaia updates
« Reply #105 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/

« Last Edit: 07/08/2017 09:04 PM by Star One »

Offline bolun

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Re: ESA - Gaia updates
« Reply #106 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://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

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Re: ESA - Gaia updates
« Reply #108 on: 12/27/2017 10:35 AM »

Offline Star One

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Re: ESA - Gaia updates
« Reply #110 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

DR2 will be 25th April 2018! 

--- Tony

Offline Star One

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Re: ESA - Gaia updates
« Reply #111 on: 02/28/2018 03:53 PM »
Chasing a stellar flash


Offline bolun

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Re: ESA - Gaia updates
« Reply #112 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/

Offline bolun

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Re: ESA - Gaia updates
« Reply #113 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/

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Re: ESA - Gaia updates
« Reply #114 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/

Offline TakeOff

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Re: ESA - Gaia updates
« Reply #115 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?

Offline jgoldader

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Re: ESA - Gaia updates
« Reply #116 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.
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Offline Star One

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Re: ESA - Gaia updates
« Reply #117 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?

Offline jgoldader

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Re: ESA - Gaia updates
« Reply #118 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!
Recovering astronomer

Offline Star One

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Re: ESA - Gaia updates
« Reply #119 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.

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #120 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

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Re: ESA - Gaia updates
« Reply #121 on: 04/06/2018 07:20 PM »
How many exoplanets will be in the April 25 Gaia data release?
I'll even excitedly look forward to "flags and footprints" and suborbital missions. Just fly...somewhere.

Offline Star One

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Re: ESA - Gaia updates
« Reply #122 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?

Offline as58

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Re: ESA - Gaia updates
« Reply #123 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.

Online hop

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Re: ESA - Gaia updates
« Reply #124 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.

Offline bolun

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Re: ESA - Gaia updates
« Reply #125 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/60147-waiting-for-gaia-s-second-data-release/

Image credit: ESA, CC BY-SA 3.0 IGO

Offline Star One

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Re: ESA - Gaia updates
« Reply #126 on: 04/07/2018 10:30 AM »
Saw this mentioned elsewhere will the standard errors be in the catalogue?

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Re: ESA - Gaia updates
« Reply #127 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

Offline Star One

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Re: ESA - Gaia updates
« Reply #128 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.

Offline Hungry4info3

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Re: ESA - Gaia updates
« Reply #129 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).

Offline Star One

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Re: ESA - Gaia updates
« Reply #130 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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #131 on: 04/21/2018 09:33 AM »
Waiting for Gaia


Offline Star One

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Re: ESA - Gaia updates
« Reply #132 on: 04/22/2018 08:15 AM »

Offline eeergo

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Re: ESA - Gaia updates
« Reply #133 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
« Last Edit: 04/25/2018 09:19 AM by eeergo »
-DaviD-

Offline eeergo

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Re: ESA - Gaia updates
« Reply #134 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
« Last Edit: 04/25/2018 09:44 AM by eeergo »
-DaviD-

Offline eeergo

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Re: ESA - Gaia updates
« Reply #135 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
« Last Edit: 04/25/2018 10:08 AM by eeergo »
-DaviD-

Offline jebbo

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Re: ESA - Gaia updates
« Reply #136 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)!

Offline bolun

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Re: ESA - Gaia updates
« Reply #137 on: 04/25/2018 10:14 AM »

Offline bolun

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Re: ESA - Gaia updates
« Reply #138 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

Offline jebbo

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Re: ESA - Gaia updates
« Reply #139 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

Offline eeergo

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Re: ESA - Gaia updates
« Reply #140 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 :)
-DaviD-

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Re: ESA - Gaia updates
« Reply #141 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.
« Last Edit: 04/25/2018 12:57 PM by jebbo »

Offline eeergo

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Re: ESA - Gaia updates
« Reply #142 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 :)
-DaviD-

Offline Star One

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Re: ESA - Gaia updates
« Reply #143 on: 04/25/2018 03:17 PM »
How many hypervelocity stars are there in the catalogue?

Offline jebbo

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Re: ESA - Gaia updates
« Reply #144 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


Offline Star One

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Re: ESA - Gaia updates
« Reply #145 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

Offline as58

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Re: ESA - Gaia updates
« Reply #146 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.

Offline jebbo

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Re: ESA - Gaia updates
« Reply #147 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

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Re: ESA - Gaia updates
« Reply #148 on: 04/25/2018 04:18 PM »
This one is also very nice, clearly showing the rotation of the galaxy.

--- Tony

Offline Star One

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ESA - Gaia updates
« Reply #149 on: 04/25/2018 05:06 PM »
Gaia second data release

« Last Edit: 04/25/2018 05:07 PM by Star One »

Offline eeergo

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Re: ESA - Gaia updates
« Reply #150 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.
-DaviD-

Offline ugordan

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Re: ESA - Gaia updates
« Reply #151 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

Offline jebbo

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Re: ESA - Gaia updates
« Reply #152 on: 04/26/2018 08:01 AM »
The papers are now available on Arxiv.  List here

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Re: ESA - Gaia updates
« Reply #153 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

Offline Star One

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Re: ESA - Gaia updates
« Reply #154 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/

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Re: ESA - Gaia updates
« Reply #155 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.

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #156 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 £4 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.


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Re: ESA - Gaia updates
« Reply #158 on: 05/01/2018 10:17 AM »
Interesting paper:

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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #159 on: 05/01/2018 04:53 PM »
Interesting paper:

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.

Offline Star One

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Re: ESA - Gaia updates
« Reply #160 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

Offline Star One

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Re: ESA - Gaia updates
« Reply #161 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

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #162 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.

Offline philw1776

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Re: ESA - Gaia updates
« Reply #163 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 %)."
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Offline Star One

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Re: ESA - Gaia updates
« Reply #164 on: 05/18/2018 03:42 PM »
ESA Euronews: Gaia’s revolution in astronomy


Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #165 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.

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #166 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.

Offline CuddlyRocket

Re: ESA - Gaia updates
« Reply #167 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? :)

Offline Ben the Space Brit

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Re: ESA - Gaia updates
« Reply #168 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?
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Offline jebbo

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Re: ESA - Gaia updates
« Reply #169 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

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #170 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)



Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #171 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>

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #172 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?

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #173 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #174 on: 08/21/2018 03:50 PM »

Offline AegeanBlue

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Re: ESA - Gaia updates
« Reply #175 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

Offline bolun

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Re: ESA - Gaia updates
« Reply #176 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

Tags: gaia