Third release of Gaia data will help astronomers reconstruct evolution of our galaxy over billions of years

The third release of data from the European Space Agency’s (ESA) Gaia mission about almost two billion stars in our galaxy has been described as a “stellar pot of gold”.

University of Cambridge astronomers are playing a leading role in analysing data from the Gaia space observatory, which features two telescopes and is located about 1.5 million kilometres from Earth.

Designed to create the most accurate and complete multi-dimensional map of the Milky Way, it will help astronomers reconstruct the structure and evolution of our galaxy over billions of years.

“This release represents a major step forward in our creation of a detailed census of our Milky Way, fully characterising a significant sample of its stellar constituents,” said Dr Nic Walton from Cambridge’s Institute of Astronomy, and member of the ESA Gaia Science Team. “Analogous to the 100,000 Genomes project in biology, we are now able to type hundreds of millions of stars, which enables us to accurately determine the life cycles from birth to death of those stars, and the incredible history and future of our Milky Way.”

New information in this release includes chemical compositions, stellar temperatures, colours, masses, ages, and radial velocities, which is the speed at which stars move towards or away from us.

“This represents the largest and most homogeneous catalogue of spectra ever published,” said Francesca De Angeli from the Institute of Astronomy. “It's like a stellar pot of gold at the end of the rainbow!”

Spectroscopy - which splits starlight into its constituent colours - helped to reveal much of this information, while data on special subsets of stars, such as those that change brightness over time, was also released.

The largest catalogue yet of binary stars, thousands of Solar System objects such as asteroids and moons of planets, and millions of galaxies and quasars outside the Milky Way were also included in the data.

A surprising discovery is that Gaia can detect starquakes that change the shapes of stars, even though it was not designed to do so. These show as tiny motions on the surface of a star. Gaia had previously found radial oscillations that cause stars to swell and shrink periodically, while keeping their spherical shape. Now it has spotted vibrations that are more like large-scale tsunamis.

Dr Walton added: “This major data release from Gaia not only allows astronomers to map the distances and motions of some two billion stars in our galaxy, but it also gives detailed measures of the physical and chemical make-up of a large number of those objects for the first time.

“With this incredible database we can build a comprehensive picture of the Milky Way and delve into its incredible history of formation, seeing direct evidence of both violent past interactions with other galaxies, and internal bouts of intense star formation along its spiral arms.

“This new data release creates a detailed bank of information, essentially working as a DNA map that allows us to understand the stellar population of our galaxy, and track its past, present and future.”

Other leading members of the Gaia UK team from the University of Cambridge include Dr Dafydd Wyn Evans, Professor Gerry Gilmore and Dr Floor van Leeuwen.

The UK team involved in the Gaia mission is supported by the UK Space Agency and the Science and Technology Facilities Council

The data can be accessed at https://gea.esac.esa.int/archive/.