Although ESA has cancelled its Eddington mission, which was to have used a precision photometer to record the transit of planets across the disks of distant stars, the agency is pressing ahead with a mission that will compile a catalog of up to a billion stars. As described in the ESA press release, the Gaia mission would be launched in 2010, and would spend almost a decade plotting these stars into a three-dimensional grid that would show not just their current position, but direction of motion, color and composition.
It always startles me how little we know about even nearby stars. It was only last year that the red dwarf SO25300.5+165258 was discovered, but at 7.8 light years away, it is the third closest star to the Sun. Projects like Gaia will be invaluable at filling in our information about other close stars that have so far evaded detection, many of them simply because of their size and dimness — some 70 percent of all stars in the galaxy are type M red dwarfs like Proxima Centauri. They’re tiny, nondescript, and when they’re close, the fact can only be uncovered by studies of their motion against background stars. We have a lot of work ahead of us just to map the immediate stellar neighborhood. And if one billion stars sounds like a lot, recall that there are some 100 billion in the galaxy at large.