The European Space Agency built this image of the Milky Way using routine data from its Gaia satellite.
Since 2013, Gaia has orbited 163,000 to 439,000 miles above Earth, on a mission to catalogue a billion stars and create a massive 3D map of the Milky Way Galaxy, which astronomers will use to study how our galaxy formed and how it has evolved to its present state.
The satellite’s control systems need a reference point to help them make sure it’s still in the correct orbit and oriented in the right direction, so it uses stars. Gaia’s systems measure how quickly certain reference stars pass across the its camera sensor, and based on that information, its attitude and orbit control systems keep the satellite in the right orbit and the right orientation.
That’s all part of what the ESA calls “housekeeping data” which Gaia beams home pretty regularly. That routine data includes information about how many stars Gaia sees every second, which tells astronomers about the density of stars in any given patch of sky.
The ESA used that data to create a gorgeous visualisation.
The bright areas are dense regions of stars, while most of dark areas have fewer stars; the result is a plane view of the Milky Way set against the darkness of intergalactic space. But the dark spots aren’t all empty; the bands of darkness that cross the bright shape of the galaxy are really huge clouds of dust and gas that block the stars from view. One day, stars may be born from that dust and gas.