Sky-scanning complete for Gaia
Gaia has a 1.0 × 0.5 m focal plane array on which light from both telescopes is projected. This in turn consists of 106 CCDs of 4500 × 1966 pixels each, for a total of 937.8 megapixels.
Neat.
The really neat part is the instrument precision. It's terrifyingly good and I have no idea how it (really) works.
- "Gaia measures their positions to an accuracy of 24 microarcseconds, comparable to measuring the diameter of a human hair at a distance of 1000 km"
https://www.esa.int/Science_Exploration/Space_Science/Gaia/C...
To nitpick with the grammar in the quote: It's capable of measuring to the accuracy of 120 μm at 1000 km. So it cannot accurately measure the diameter of a human hair (which ranges from around 20 to 200 μm) at that distance, but only to the accuracy of a human hair.
You're right: this precision is hundreds of times below the diffraction limit of even the James Webb telescope. It can't possibly measure the width of an object that finely; rather, only the relative displacement of its centroid position between two points in time. (And it's a seriously confusing physics miracle that that much is possible).
Isn't that just the distance between pixels and the image projected onto them?
Probably not. The accuracy with which you know the pointing of the telescope probably also plays into it (unless the FOV is large enough to have other stars as a reference?), and you can do subpixel positioning of objects to get more accuracy than full pixel steps.
No: it's far weirder and I'm not knowledgeable enough to explain it.
IIRC Gaia had a performance degradation because of stray light, probably ice on the border of it's aperture[1].
How has that affected this result?
[1] https://blogs.esa.int/gaia/2014/06/16/preliminary-analysis-o...
It was not ice, but fibers from the sun shield. The ice issue was resolved by heating the satellite. The stray light issue affected spectra measurements, but not the astrometric side of the mission
I wonder if it could keep giving us useful data without the precision rotation? Intuitively it seems like we should be able to figure out where it's pointing by star-matching plus dead reckoning based on the last frame.
It's possible...but the point of this instrument is to measure star locations very precisely. It probably has a star tracker for positioning doing what you're suggesting. If you were to use that type of positioning info you could introduce inaccuracies into the measured data eventually.
Also, every mission comes to an end eventually - better to do it in the right way and have the right amount of propellent saved for either a graveyard orbit or de-orbiting. It met the mission timeline and goals.
Yea ok. Still, it seems like it could produce a lot of very useful data if switched to a blind spinning mode.
The current coordinate system is based on extremely distant radio sources. Ground based scopes found some bright galactic sources which GAIA aligned to, and is measuring everything relative to those. And now GAIA is the defining source of the ICRS for optical observations.
Hope they have captured an image of Planet Nine somewhere there, and eventually are able to pinpoint it.
Farewell, friend. Hello, LSST.
And now to use the data to make the most realistic scifi game. With correct stellar motion during relativistic travel.
Elite Dangerous already has more known star systems (160k) in the Milky Way than you can realistically visit - and the rest (400 billion) filled in with plausibly simulated systems: https://elite-dangerous.fandom.com/wiki/Galaxy#Milky_Way - it even kind-of predicted a star system that was only discovered after the game was released: https://elite-dangerous.fandom.com/wiki/Trappist-1#Impact_of...
I didn’t realize a game actually used an approach like this, really cool. Reminds me of the simulated MMORG world in Neal Stephenson’s README, where they tried to simulate the formation of the planet to get realistic mineral deposits and topology.
REAMDE
Oops, thanks!
Now that most stars are mapped, next step: map all the planets.
I really wish they would have identified Gaia as some kind of satellite. Gaia is also a name for Earth itself.
You may want to know: the high-res images which are offered for downloading contain the same image which is shown on the page, that is, the infographic.
Not worth the download, as I thought that it would contain a huge panorama of the sky.
For real data you can use Gaia ESA archive: https://gea.esac.esa.int/archive/
I went to study MSc in Space Science and Technology as a hobby few years ago. In one course (2022) we had an assignment to find Supernovae from recent Gaia data (Python code). Then made sure this is observable by University’s robotic telescope (and compliant with local weather forecast). Next requested the observation from the telescope and if successful, received the pictures next day. Had to analyse the results as well. It surprised me how much data there actually is available in quite open format from ESA missions.
Controlling remote telescope few thousand kilometres away was also a nice experience.
The downlinked data is claimed to be 142TB compressed. I suspect that the huge panorama might be a little big for your computer.
Direct link to some very very nice images and animations: https://www.esa.int/Science_Exploration/Space_Science/Gaia
Two of my favorites: https://www.esa.int/ESA_Multimedia/Images/2025/The_best_Milk...
https://www.esa.int/ESA_Multimedia/Images/2025/01/The_best_M...
I get how Gaia could make the best edge on image, but how could Gaia (or anything man made) get the the "best" face on image?
The whole purpose of Gaia is to precisely measure the position of stars (and other objects). Once positions are known, a 3D model can be built. But how are the distances measured? The answer is parallax, essentially triangulation. You look for very small changes of position against the background sky. You use the width of the earth's orbit as the baseline and measure at different times of the year.
All of these are "Artist's Impressions". My best guess is they run a simulation based on the data from the spacecraft and then can pan the camera around as they see fit
"The best Milky Way map, by Gaia (edge-on)"
The "by Gaia" implies the opposite to me. Unless the "artist's impressions" are from someone named Gaia???
From the page:
[Image Description: A model image of what our home galaxy, the Milky Way, might look like edge-on, against a pitch-black backdrop. The Milky Way’s disc appears in the centre of the image, as a thin, dark-brown line spanning from left to right, with the hint of a wave in it. The line appears to be etched into a thin glowing layer of silver sand, that makes it look as if it was drawn with a coloured pencil on coarse paper. The bulge of the galaxy sits like a glowing, see-through pearl in the shape of a sphere in the centre of this brown line.]