ESA’s Gaia satellite is shooting the stars, to create the largest stellar sky map ever.
The 3D catalogue includes the precise location and brightness of 1,142 million stars in the Milky Way, and maps the motion across the sky for more than two million of those. It’s twice as precise as the previous definitive reference, the Hipparcos Catalogue, and contains 20 times as many stars.
"The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations," says Timo Prusti, Gaia project scientist at ESA. "Although the current data are preliminary, we wanted to make them available for the astronomical community to use as soon as possible."
The data was collected in the first 14 months of the Gaia satellite’s five-year mission, which started in July 2014. When more data is added, the stripes and other artefacts present in the map, which occur as a result of how Gaia scans the sky, will gradually disappear.
Gaia uses a camera powerful enough to work out the diameter of a strand of human hair from 1,000 kilometres away. The raw data was converted to accurate distances and positions by the Gaia Data Processing and Analysis Consortium, a European collaboration of 450 scientists and software engineers.
They were able to locate 386 previously undiscovered stars, and detect 3,194 variable stars, which swell and shrink leading to regular periodic brightness changes. These are particularly useful as cosmic distance indicators.
"Gaia is at the forefront of astrometry, charting the sky at precisions that have never been achieved before," says Alvaro Giménez, ESA's Director of Science. "Today's release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our Galaxy."
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