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takyon writes:

The European Space Agency's Gaia mission has released data on 1.7 billion stars, including velocity data for 7 million:

Wednesday was the day astronomers said goodbye to the old Milky Way they had known and loved and hello to a new view of our home galaxy. A European Space Agency mission called Gaia just released a long-awaited treasure trove of data: precise measurements of 1.7 billion stars. It's unprecedented for scientists to know the exact brightness, distances, motions and colors of more than a billion stars. The information will yield the best three-dimensional map of our galaxy ever.

"This is a very big deal. I've been working on trying to understand the Milky Way and the formation of the Milky Way for a large fraction of my scientific career, and the amount of information this is revealing in some sense is thousands or even hundreds of thousands of times larger than any amount of information we've had previously," said David Hogg, an astrophysicist at New York University and the Flatiron Institute. "We're really talking about an immense change to our knowledge about the Milky Way."

Also included are the precise positions of more than 14,000 known asteroids, with more asteroids promised in future data releases.

About the data release:

The second data release (DR2), currently scheduled for 25 April 2018, will be based on 22 months of observations made between 25 July 2014 and 23 May 2016. It will include positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 200 million stars, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 6 million stars between magnitude 4 and 13. It will also contain data for over 13,000 selected Solar System objects. Since the data processing procedure links individual Gaia observations with particular sources on the sky, in some cases the association of observations with sources will be different in the second data release. Consequently some source identification numbers will be different in DR2 than in DR1. The third data release potentially will include orbital solutions for many binary stars and classifications for spectroscopically "well behaved" objects, as well as improved positions, parallaxes and proper motions. The fourth data release potentially will include variable star classifications, complete Solar System results, and non single-star catalogues. The complete final Gaia catalogue is currently scheduled for 2022, three years after the end of the nominal five-year mission. It would be pushed back if the mission is extended to nine years. The number of releases between DR2 and the final release has not yet been decided.

Also at ESA, Science Magazine, and The Verge.

Previously: European Space Agency's Gaia Spacecraft Maps Over a Billion Stars in the Milky Way
ESA's Second Batch of Gaia Data Coming in April 2018

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