ESA space probe creates richest Milky Way map

A multitude of discoveries are on the horizon after this much awaited release, which is based on 22 months of charting the sky.

The new data includes positions, distance indicators and motions of more than one billion stars, along with high-precision measurements of asteroids within our solar system and stars beyond our own Milky Way galaxy.

Preliminary analysis of data from ESA's Gaia space observatory reveals fine details about the make-up of the Milky Way's stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

"The observations collected by Gaia are redefining the foundations of astronomy," said Gunther Hasinger, ESA Director of Science.

Gaia was launched in December 2013 and started science operations the following year. The first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars.

The latest data release, which covers the period between July 25, 2014 and May 23, 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision.

For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.

With these accurate measurements it is possible to separate the parallax of stars - an apparent shift on the sky caused by Earth's yearly orbit around the Sun - from their true movements through the Galaxy. The new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars.

From the most accurate parallax measurements, about ten per cent of the total, astronomers can directly estimate distances to individual stars.

"The second Gaia data release represents a huge leap forward with respect to ESA's Hipparcos satellite, Gaia's predecessor and the first space mission for astrometry, which surveyed some 118,000 stars almost thirty years ago," said Anthony Brown of Leiden University, The Netherlands.

"The sheer number of stars alone, with their positions and motions, would make Gaia's new catalogue already quite astonishing," said Brown.

"But there is more: this unique scientific catalogue includes many other data types, with information about the properties of the stars and other celestial objects, making this release truly exceptional," he said.