ESA - Gaia updates

[AegeanBlue]

GaiaNIR White Paper

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

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

[Star One]

GaiaNIR White Paper

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

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

I can’t see them still using Soyuz as a launcher in twenty years time. On that kind of timescale I expect to see a very different launcher market so it’s curious they treat this as a static item in the paper.

[russianhalo117]

GaiaNIR White Paper

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

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

I can’t see them still using Soyuz as a launcher in twenty years time. On that kind of timescale I expect to see a very different launcher market so it’s curious they treat this as a static item in the paper.

it is just a baselined launcher. You don't list launchers that are not in service that are in design.

[sdsds]

it is just a baselined launcher. You don't list launchers that are not in service that are in design.

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

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

[yoram]

GaiaNIR White Paper

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

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

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

[AegeanBlue]

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

[/quote]

It did take 20 years to go from HIPPARCOS to Gaia. They are using their computer resources to actually create the Gaia catalogue. While I have not read the original Gaia proposal, I am pretty sure it looked more like HIPPARCOS than what Gaia did eventually look like. Also they say that they need technology to advance to create time integration NIR sensors good enough and since they would like to keep it as an M class mission they would rather bring on board the Americans or the Japanese who are more advanced in these sensors.

[Alpha_Centauri]

it is just a baselined launcher. You don't list launchers that are not in service that are in design.

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

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

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

Even with US or Japanese involvement, as an institutional mission there will have to be a European backup launcher, and I can't see Europe using extra-large fairings any time soon.

[Dizzy_RHESSI]

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

The longer the separation is between Gaia and GaiaNIR, the better the measurements of proper motions will be. If you observe over a longer baseline in time the change in angular position becomes larger. But the real reason is simply the timing of mission opportunities. Slots for ESA's Cosmic Vision program have already been filled, and the next opportunities to open up will not see a mission fly before ~2040. The science theme of astrometry was submitted to the L2/L3 selection, but it was unsuccessful. These opportunities are far too competitive to fly two astrometry missions back-to-back. It could happen as a NASA mission sooner, but I think that's quite unlikely given that it would fall in the gap between strategic missions and MIDEX/SMEX competitions.

[Star One]

There Should be About 7 Interstellar Objects Passing Through the Inner Solar System Every Year.

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

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

https://arxiv.org/abs/2103.03289

https://www.universetoday.com/150478/there-should-be-about-7-interstellar-objects-passing-through-the-inner-solar-system-every-year/

[bolun]

12 RARE EINSTEIN CROSSES DISCOVERED WITH GAIA

7 April 2021

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

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

Credits: The GraL Collaboration & R. Hurt (IPAC/Caltech)/The GraL Collaboration

[AegeanBlue]

Gaia Might Even be Able to Detect the Gravitational Wave Background of the Universe

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

There is also another news item today which I have not been able to access today being behind the agency firewall about using LAMOST to improve accuracy

[Star One]

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) has helped Gaia achieve millimagnitude (mmag) precision in photometry, according to a study led by researchers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) and Beijing Normal University (BNU)

https://eurekalert.org/pub_releases/2021-05/caos-lhg051121.php

[AegeanBlue]

Gaia is still the gift that keeps on giving. There was a paper on arxiv that I got to though via twitter about mapping the Local Group of Galaxies membership, their relationship and what globular clusters belong to which galaxy (including finding new ones) based on Gaia maps. But this is not what I am here to share.

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



What they do is create the catalog of stars and the scientists talk about how they calibrate the data, take into account relativistic effects and sensor / spacecraft calibration etc. Quite interesting

[AegeanBlue]

This is a bit old news but no one has posted it here. Gaia discovered a cavity in the Milky Way galaxy:

https://www.cosmos.esa.int/web/gaia/iow_20210922

[AegeanBlue]

Astrometric mass ratios of 248 long-period binary stars resolved in Hipparcos and Gaia EDR3

https://arxiv.org/abs/2109.11951

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

Gaia is to produce a very comprehensive catalog of stars up to 20th-21st magnitude or so. EDR3 and thus DR3 has 1.8 billion stars with the number somewhat increased from DR2 due to improvements at the bright end, the dim end, crowded regions but most importantly at multiple stars being resolved. Yes this paper shows that many of the higher order stars in the much more manageable Hipparcos Catalogue are even higher order with unresolved companions. While DR4 will be improved and might show some of these hidden companions, the authors suggest that GAIANIR, the followup mission in another 20 years, will be better for resolving several issues.

[AegeanBlue]

At the virtual European Astronomical Society meeting there were presentations on the full DR3 and they set up a page describing it here:

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

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

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

There will be ca 158,000 of which 99.1% are already known, so few new asteroids. My guess is that they are still refining the discovery pipeline

[Yiosie]

Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space [dated Nov. 24]

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

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

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

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

[Arb]

Gaia reveals that most Milky Way companion galaxies are newcomers to our corner of space [dated Nov. 24]

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

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

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

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

The linked article is worth reading to the end - its penultimate paragraph includes this:

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

Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8

[ttle2]

Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8

Like 99% of new astrophysics articles, it's available on arXiv: https://arxiv.org/abs/2109.11557

[deadman1204]

Original paper (subscription needed to go beyond abstract): https://iopscience.iop.org/article/10.3847/1538-4357/ac27a8

Like 99% of new astrophysics articles, it's available on arXiv: https://arxiv.org/abs/2109.11557

Doesn't the arXiv only have the original submission? Not all the changes from review and such?