UK astronomers contribute to 3D map of a billion stars
25 Apr 2018



British astronomers working on the international space mission Gaia have contributed to a revolution in our understanding of the Milky Way with the release today of a new 3-D map of over one billion stars in our Galaxy.

​​​Gaia’s view of the sky​
(Credit: DPAC/ESA)

The Gaia data is a globally accessible resource that is available for anyone to study, not just professional astronomers.

In the year 1610 one person on the planet, Galileo Galilei, used a telescope to study the Milky Way and discovered that it was composed of a huge number of faint stars. Now four hundred years on everyone has an opportunity to study the Milky Way and the celestial bodies that it contains in detail thanks to the latest data release from the European Space Agency (ESA) Gaia mission.

Unlike other major space missions a very special aspect of the Gaia mission is that the teams involved do not keep the results for their own science interests. Instead the Gaia data is released with free access to everyone for analysis and discovery. This means that amateur astronomers from school age and up have as good an opportunity as anyone of finding new supernovae or to do real science with transients.

The Milky Way taken by the Gaia spacecraft.

The detailed information that Gaia has collected in this latest census of over one billion stars allows their positions and distances to be mapped to unprecedented precision giving us a true 3-dimensional map of our Milky Way Galaxy.

This new release of information is showing us 600 times more stars than previously available, covering a volume 1000 times larger than Gaia’s own first data release two years ago, with precision some one hundred times improved. These results allow enhanced study of almost all branches of astronomy: from traces of the formation of the Solar System; through how stars evolve; through the current structure, the assembly and evolutionary history of the Milky Way; to mapping the distribution of Dark Matter in the Galaxy; to establishing the distance scale in the Universe; to discovery of rare objects.

This second data release allows progress in all these studies by providing not only distances and apparent motions across the sky for 1.3billion sources, but also very precise measurements of brightness and colour for an even larger catalogue of 1.7billion sources. Seven million stars have their line of sight velocities measured, providing full 6-dimensional – 3 space positions, 3 space motions – information, determining full orbits for those stars in the Milky Way. This is the information needed to weigh the Galaxy, and determine the distribution – and perhaps the properties – of Dark Matter, the mysterious substance which dominates the mass of the Galaxy and the Universe.​

UK Science Minister Sam Gyimah said: “Projects such as GAIA, which is mapping over one billion stars and producing a 3D map of our Milky Way, demonstrate human endeavour and exploration at its best. The truly remarkable new project will help inspire people all over the world, from professional scientists to amateur star gazers, making it easier than ever before to navigate the sky above us.

“This project is further proof that the UK space sector, and the scientists who work in it, are truly world-leading, and through the government’s modern Industrial Strategy we are realising the opportunities available, helpin​g to build a Britain fit for the future.”

The unique mission is reliant on the work of UK teams at the Universities of Cambridge, Edinburgh, Leicester, Bristol, the Mullard Space Science Laboratory (MSSL) at UCL London and the Science and Technology Facilities Council’s (STFC) RAL Space facility, all of whom are contributing to the processing of the vast amounts of data from Gaia, in collaboration with industrial and academic partners from across Europe.

“The combination of all these unprecedented measures provides the information for astronomers to take the next big steps in mapping the formation history and evolutions of stars and our Milky Way Galaxy. There is hardly a branch of astrophysics which will not be revolutionised by Gaia data. The global community will advance our understanding of what we see, where it came from, what it is made from, how it is changing. All this is made freely available to everyone, based on the dedicated efforts of hundreds of people. There are so many exciting things to do better with the exquisite Gaia data we anticipate new science papers appearing every day after this release.” said Professor Gerry Gilmore from the University of Cambridge, UK Principal Investigator for the UK participation in the Gaia Data Processing and Analysis Consortium, and one of the original proposers of the mission to ESA.

Professor Mark Cropper leads the team at Mullard Space Science Laboratory/UCL that made the UK contribution to the spectroscopic processing effort and said “We use Gaia to measure the Milky Way, star by star - where they were born, how they were generated, what their temperatures are and their radial velocity. It’s given us direct evidence of the rotation of our galaxy and opens the door to many more detailed studies on the way other disk galaxies evolve. So far, we’ve calculated the radial velocities of over 7 million stars from analysing nearly 20 billion separate spectra, which is a demanding but worthwhile process! These numbers are only set to increase – most likely up to 100 million stars – as we analyse more distant, fainter stars, and we eagerly anticipate what else Gaia uncovers.”

Dr Floor van Leeuwen from the University of Cambridge has been Project Manager for the UK and European photometric processing work, and is a leading co-author on the example science papers illustrating Gaia’s impact on our knowledge of star clusters and satellite galaxies in the outer Milky Way. Speaking of the new findings he said “Groups of dwarf galaxies, including the Magellanic Clouds, can now be observed to be moving around in very similar orbits, hinting at a shared formation history. The accurate observed motions and positions of the globular clusters and dwarf galaxies provide tracers of the overall mass distribution of our galaxy in a way that has not been possible with this level of accuracy before.”

STFC helped the set-up of the data applications centre for the project and STFC’s current support involves the UK exploitation of the scientific data that is now being yielded from the mission. In addition the photometric data processing software to which STFC contributed, as part of the UK-led team, offers the ability to precisely measure the brightness of the billion objects that GAIA is observing, while contributions from the rest of Europe are charting the positions, distances and movements of those one billion stars.

Professor Ian McCrea, Space Physics and Operations Division Head at STFC's RAL Space said, "Four years into the Gaia mission and it is incredible to see that our work in the UK on developing the photometric data processing software, that precisely measures the brightness of the billion objects that GAIA is seeing, is now successfully giving us comprehensive and detailed information that helps us better understand our true place in the Milky Way, our home galaxy. With this new data release and those that will follow, I am excited to see what new celestial objects, such as extra-solar planets, brown dwarfs, supernovae, asteroids, and of course, things that we have not even imagined have now been recorded."

UK participation in the mission itself has been funded by the UK Space Agency and scientists and engineers from around the UK played key roles in the design and build of Gaia.

The UK Space Agency has already contributed £15 million to Gaia and is committed to spending a further £4 million on processing and analysing the data. Dr Graham Turnock, Chief Executive of the UK Space Agency, said: “We’re working with industry and academia to support cutting-edge science that will lead to new discoveries about our Galaxy. The UK involvement in this exciting mission shows that our academics and engineers are world leaders in the space sector. As part of ESA we will continue to be at the forefront of research and deeply involved in missions such as ExoMars, with its Airbus-built rover, and the BepiColombo mission to Mercury.”

Gaia orbits the sun at a distance of 1.5 million kilometres from the earth and was launched by the European Space Agency in December 2013 with the aim of observing a billion stars and revolutionising our understanding of the Milky Way.