Its written in the stars

Astronomers today opened one of the last remaining windows on the Universe, publishing the first full 3D census of over one billion stars in our Milky Way.

The European Space Agency Gaia mission has provided the information for astronomers to map the true 3-dimensional structure of our Milky Way Galaxy, with over one billion stars having their positions and distances published to unprecedented precision. This is some 600 times more stars than previously available, covering a volume 1,000 times larger than Gaia’s own first data release, with precision some one hundred times improved.

Leicester has been part of the Gaia Data Processing and Analysis Consortium (DPAC) since the project started. Funding for the Leicester work has been running for some 15 years with Professor Martin Barstow as Principal Investigator. Professor Barstow is Pro-Vice-Chancellor, Strategic Science Projects Director, Leicester Institute of Space and Earth Observation and Professor of Astrophysics & Space Science.

He said: “After 15 years of intense work, this new release of data from the ESA Gaia space mission will provide the most accurate map ever of the positions and distances of more than a billion stars in the Milky Way. Its impact will be like a tidal wave through all of astronomy, transforming everything we know… or think we know about the Universe.”

The University team has a critical role in the mission – they are responsible for understanding and compensating for radiation damage that affects the on-board sensors. If this isn’t done, all the critical science from the mission would be degraded. Professor Barstow also have a science interest, as Gaia observations of white dwarf stars will have a major impact on his research. He is a key contributor to one of the papers that will be released along with the data archive on 25 April.

The paper relates to the relation between the intrinsic brightness of a star and its colour (Hertzprung-Russell diagram) which can be mapped with Gaia’s exquisite measures of both parameters, illustrating the evolution of stars from birth to death. Professor Barstow is a senior co-author of this illustration science paper.

He said:  “The huge sample, accurate luminosities and colours, make visible for the first time features in stellar evolution which we have suspected but never seen. For example, we can now see directly the late evolution of stars, once they have ejected their envelopes and become dead cores – white dwarfs – cooling rapidly onto sequences which depend on the chemical element distributions, arising from the lifecycle of the parent star. This is superb confirmation of stellar theory, and has the precision and numbers to allow us to further refine and test our understanding of the end-point of stars like our own Sun.”

Others who have been involved over the years in the project while at Leicester are Claudio Pagani, Steve Sembay, Andy Read, Duncan Fyffe and Patricio Ortiz.

Researchers say these results allow improved 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.

The UK has been a major partner in the Gaia mission since its proposal, with significant involvement in spacecraft design and construction, especially by Airbus Defence and Space (Stevenage), and through provision of the sensors for Gaia’s billion-pixel camera, by Teledyne-e2v (Chelmsford). Several UK teams have key roles in processing the data. Cambridge, supported by the UK Space Agency and STFC, hosts one of the six data processing centres with responsibility for the brightness, colour and spectrophotometry (for DR3) data.