Question: How does the Gaia Satellite work and what does it do?

Heather Campbell answered on 11 Nov 2014:

Gaia is mainly trying to make a 3D map our Milky Way galaxy and to do that it measures the distances to stars very accurately, the same as measuring the width of a human hair in Pairs from London.

Gaia measures the distance using something called parallax. It is the same reason we have two eye. If you hold your thumb out in front of you and close one eye and then the other it appears to move compared to things much further away from you. You can then use trigonometry to work out how far away your thumb (or a star) is, as you know the distance between your eyes (or between the satellites orbit) which forms the base of the triangle and then you meausre the shift as an angle and you can see how far away the object is.

We can do that with the stars, Gaia will look at their position compared to objects very far away, called quasars, and it will do this many (~70 over 5 years) times from different positions in Gaia’s orbit (around our sun, outside of the earths orbit, another 1.5million km further away from the sun). We need to look so many times as all the stars are moving in the galaxy, orbiting around within the galaxy. And many of the stars will have planets around them which makes the star looks like its wobbling. So to measure the distance to the stars we have to also account for there motion.

To do all this the Gaia satellite has two main mirrors on it (so its like two telescopes in space), which are about 1.5m by 0.5m. Its has a huge camera, the largest flown in space, about the size of a table top, with about 1billion pixels in it (compared to about 10million in a camera on your phone). There are also prisms on board to measure physical properties of the stars, like the temperature and surface gravity, and a very accurate spectrograph to measure how the stars move towards and away from us.

Its also looking for new object (e.g. explosions of stars) and this part of the project is called gaia science alerts, which is what I work on and we’re announcing to these new things as soon as we see them to public, so everyone can join in.

To find out much more information see gaia.ac.uk