Nature reports on the Gaia space telescope’s new map that will pinpoint more than a billion objects by the time it’s done:
Gaia, a space telescope launched by the European Space Agency (ESA) in late 2013, will release its first map of the Milky Way on 14 September. The catalogue will show the 3D positions of 2,057,050 stars and other objects, and how those positions have changed over the past two decades. Eventually, the map will contain one billion objects or more and will be 1,000 times more extensive and at least 10 times more precise than anything that came before.
Some groups have planned ‘Gaia hacking’ and ‘Gaia sprint’ events, at which researchers will collectively work out how best to exploit the sudden manna. “Gaia is going to revolutionize what we know about stars and the Galaxy,” says David Hogg, an astronomer at New York University who is leading some of these efforts. So what are some of the revelations that Gaia could make?
Gaia’s 3D view of the Milky Way in motion will reveal how stars move under its combined gravitational pull. This will add to knowledge of the Galaxy’s structure, including parts that are not directly visible from Earth, such as the ‘bar’ — two arms that stick straight out of the Galactic Centre and join it to the spiral arms.
Researchers will be able to identify ‘outlier’ groups of stars which stream together at high speeds, and which are thought to be remnants of mergers with smaller galaxies, says Michael Perryman, an astronomer at University College Dublin and a former senior scientist for Gaia at ESA. Combined with existing information about factors including stars’ colour, temperature and chemical composition, this detailed map will enable researchers to reconstruct the Galaxy’s archaeology: how it got to its present state over the past 13 billion years. “Over its lifetime, Gaia is going to radically impact our understanding of the structure of the Milky Way and its evolutionary history,” says Monica Valluri, an astronomer at the University of Michigan in Ann Arbor.
The details of star trajectories inside the Galaxy will reveal the distribution not only of visible matter, but also of dark matter, which constitutes the bulk of most galaxies’ mass. And that in turn could help to reveal what dark matter is.
Astronomers have discovered thousands of planets orbiting other stars, in most cases by detecting tiny dips in a star’s brightness when an orbiting planet passes in front of, or ‘transits’, it. Gaia will detect planets using another method: measuring slight wobbles in the star’s position caused by a planet’s gravitational pull.
“It seems like a good bet that the mission will reveal thousands of new worlds,” says Gregory Laughlin, an astronomer at Yale University in New Haven, Connecticut.
As it constantly scans the sky, Gaia will also track and discover things much closer to home. It is ultimately expected to observe some 350,000 asteroids inside the Solar System, and to discover hundreds of new ones, says Gaia astronomer Paolo Tanga of the Côte d’Azur Observatory in Nice, France. These will include near-Earth objects (NEOs), those whose orbits bring them within about 200 million kilometres of Earth.
When it spots an NEO, Gaia can alert observatories, which can then use ground-based telescopes to establish whether the object is a threat.