More than a billion stars in the Milky Way mapped

An all-sky view of stars in the Milky Way and nearby galaxies, based on the first year of observations from ESA's Gaia satellite.
An all-sky view of stars in the Milky Way and nearby galaxies, based on the first year of observations from ESA's Gaia satellite.PHOTO: AGENCE FRANCE-PRESSE

The Gaia space probe, launched in 2013, has vastly expanded the inventory of known stars

PARIS • The Gaia space probe, launched in 2013, has mapped more than a billion stars in the Milky Way, vastly expanding the inventory of known stars in our galaxy, the European Space Agency (ESA) said.

Released to eagerly waiting astronomers around the world, the initial catalogue of 1.15 billion stars is "both the largest and the most accurate full-sky map ever produced", said French astronomer Francois Mignard, a member of the 450- strong Gaia consortium.

In a Web-cast press conference at the ESA Astronomy Centre in Madrid yesterday, scientists unveiled a stunning map of the Milky Way, including stars up to half a million times fainter than those that can be seen with the naked eye.

The images were captured by Gaia's twin telescopes - scanning the heavens over and over - and a billion-pixel camera, the largest-ever put into space.

The resolution is sharp enough to gauge the diameter of a human hair at a distance of 1,000km, said Dr Anthony Brown, head of the Gaia data processing and analysis team.

Gaia maps the position of the Milky Way's stars in a couple of ways. Not only does it pinpoint their location, but also the probe - by scanning each star multiple times - can plot their movement.

The data release includes both kinds of data for some two million stars. A Web portal (http://gea.esac.esa.int/archive/) has been opened where anyone can play with Gaia data and look for novel phenomena.

But over the course of Gaia's five-year mission, that catalogue is set to expand 500-fold - still only 1 per cent of the Milky Way's total 100 billion stars.

Orbiting the Sun 1.5 million km beyond Earth's orbit, the European probe started collecting data in July 2014. One eagerly anticipated measurement is the radial velocity of stars. This describes the movement they make towards or away from Gaia as they turn around the galaxy.

If this measurement is combined with the stars' proper motion, it will lay bare the dynamics of the Milky Way, said BBC.

Astrophysicists hope to learn more about dark matter, the invisible substance thought to hold the observable Universe together.

They also plan to test Albert Einstein's theory of general relativity by watching how light is deflected by the Sun and its planets.

"There is a new revolution coming," said Dr Antonella Vallenari, a member of the Gaia team.

"Gaia is meant to answer a fundamental question: How was our galaxy formed?"

AGENCE FRANCE-PRESSE

A version of this article appeared in the print edition of The Straits Times on September 15, 2016, with the headline 'More than a billion stars in the Milky Way mapped'. Print Edition | Subscribe