A massive new harvest of astronomical data

The European Space Agency has released a new tranche of processed data from the Gaia space observatory – the result of several years’ work by hundreds of scientists, including a team at the Institute for Astronomy.

220 million spectra

On June 13th 2022 the European Space Agency releases a new tranche of processed data from the Gaia space observatory to the world scientific community. The release incorporates a rich variety of position, distance, spectroscopic and classification information for hundreds of thousands of solar system objects, 1.6 billion stars (including nearly ten million variable types and one million binaries), and millions of candidate galaxies and distant quasars. The spectroscopy alone amounts to some 220 million individual spectra, by far the largest haul of such data ever assembled. The data release is the result of several years’ work by hundreds of European scientists including a team at the Institute for Astronomy, based in the School of Physics and Astronomy.


The European Space Agency's Gaia space observatory has been scanning the entire sky since mid-2014, making position and brightness measurements as objects transit its focal plane.

Many hundreds of individual measurements for each of several billion objects have been amassed over the last seven years, and the satellite is still going strong with a projected life time now estimated at 10 years in total. Raw data from the giga-pixel cameras on-board is transmitted continuously to the ground where a network of data processing centres calibrate and prepare the data for science exploitation by the world astronomical community.

Edinburgh scientists and technical experts in the Institute for Astronomy are involved in this endeavour which is staffed by several hundred scientists, engineers and operations personnel spread around Europe. The UK part of the collaboration involves the universities of Edinburgh, Cambridge, Leicester, Bristol and University College London. Here in Edinburgh responsibilities include instrumental calibrations and core processing software for the imaging systems at the head of the data flow, and also preparing the final science-ready data products and delivery systems at the tails of the pipelines, all in collaboration with colleagues in the pan-European Gaia Data Processing and Analysis Consortium.


The Gaia telescopes and detection systems are highly complex and the data streams require much detailed treatment to extract the best possible measurements. Many repeat cycles of pipeline processing involving iteratively refined software must be undertaken in order to reach the ultimate precision which, in terms of position alone, is equivalent to resolving 3 cm sized features at the distance of the Moon (e.g. the width of a Lunar astronaut's gloved finger seen from Earth!).

Data release 3

Periodic data releases started in September 2016 and occurred at two-yearly intervals thereafter, each presenting increasing amounts of data and increasingly advanced data products. The latest, Data Release 3, occurs on June 13th this year and amounts to some 10 terabytes of products from measurements taken in the first three years of the mission. This latest release is a major milestone in that, for the first time, calibrated spectra for a significant fraction of the entire billion-source catalogue are provided, in addition to detailed astrophysical parameters for nearly half a billion sources enabling categorisation of their stellar types (luminosities, radii, etc). Nearly 34 million stars are provided with line-of-sight velocities from Doppler shift measurements of the lines in their high-resolution spectra, the largest radial velocity survey ever created. In conjunction with the positions, distances and angular movement of those stars this yields a full "six-dimensional" view of their locations and space velocities within the Milky Way. The release includes detailed data for around one million multiple star systems where two or more stars are in close orbits around each other. This supersedes all work on such systems undertaken in astronomy in the centuries since the invention of the telescope. These are just a few examples from the treasury of Gaia Data Release 3 - further details of the release are given in the links below.

Dr. Nick Rowell, Institute for Astronomy, School of Physics and Astronomy said:

The Gaia space telescope scans the sky 24 hours a day, measuring and cataloging every object bright enough to be detected by its sensors. This ranges from asteroids in the Solar System, through nearby stars, all the way to quasars in the distant universe.

Dr. Nigel Hambly, Institute for Astronomy, School of Physics and Astronomy, said:

Gaia is the mission that keeps on giving. Data releases up to now have yielded on average four to five research papers per day in international journals of research in astronomy and astrophysics. This is a figure that even surpasses that for the NASA/ESA Hubble Space Telescope. The mission is literally re-writing astronomy text books, but we're nowhere near the end yet. The latest release of data comprises merely 30% of the measurements in the projected final mission catalogue, yet it is nonetheless a huge leap forward in astronomical survey science.