Gaia: Astronomers will release the most accurate data ever for nearly two billion stars

On December 3, an international team of astronomers will announce the most detailed catalog of stars ever made in a vast swath of our galaxy, the Milky Way. Measurements of stellar positions, movement, brightness and colors are in the third first data release from the European Space Agency’s Gaia Space Observatory and will be available to the public. Early results include the first optical measurement of the solar system’s acceleration. The dataset and early scientific findings will be presented in a special briefing hosted by the Royal Astronomical Society.

Launched in 2013, Gaia operates in an orbit around the so-called Lagrange point 2 (L2), located 1.5 million kilometers behind the Earth in the direction away from the Sun. At L2 the gravitational forces between the Earth and the Sun are balanced , then the spacecraft remains in a stable position, allowing an essentially unobstructed long-term view of the sky.

Gaia’s main goal is to measure stellar distances using the parallax method. In this case, astronomers use the observatory to continuously scan the sky, measuring the apparent change in the position of the stars over time, resulting from the movement of the Earth around the Sun.

Knowing that minuscule shift in the positions of the stars makes it possible to calculate their distances. On Earth this is made more difficult by the blurring of the Earth’s atmosphere, but in space measurements are limited only by the telescope optics.

Two previous versions included the positions of 1.6 billion stars. This version brings the total to just under 2 billion stars, whose positions are significantly more accurate than previous data. Gaia also tracks the brightness and changing positions of stars over time along the line of sight (their so-called proper motion) and, by breaking down their light into spectra, measures the speed at which they are moving towards o Chemical composition.

The new data includes exceptionally accurate measurements of the 300,000 stars within 326 light years closest to the Sun. Researchers use this data to predict how the background of stars will change over the next 1.6 million years. They also confirm that the solar system is accelerating in its orbit around the galaxy.

This acceleration is delicate and is what one would expect from a system in a circular orbit. In one year, the Sun accelerates towards the center of the Galaxy by 7 mm per second, compared to its speed along its orbit of about 230 kilometers per second.

Gaia’s data also deconstructs the Milky Way’s two largest companion galaxies, the Small and Large Magellanic Clouds, allowing researchers to see their different stellar populations. A dramatic visualization shows these subsets and the star bridge between the two systems.

Dr Floor van Leeuwen of the Institute of Astronomy at Cambridge University and the manager of the Gaia DPAC project in the UK comment: “Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away. distance, with an accuracy equivalent to measuring hair thickness at a distance of over 2,000 kilometers. These data are one of the cornerstones of astrophysics, allowing us to forensically analyze our stellar neighborhood and address crucial questions about origin and future of our Galaxy “.

Gaia will continue to collect data until at least 2022, with a possible mission extension to 2025. Final data releases are expected to provide stellar positions 1.9 times more accurate than those released so far, and more than 7 times more correct movements. accurate, in a catalog of over 2 billion objects.

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Scientific contacts

Professor Gerry Gilmore

Institute of Astronomy

Cambridge University

Tel: +44 (0) 1223 337506

[email protected]

Dr Floor van Leeuwen

Institute of Astronomy

Cambridge University

Tel: +44 (0) 1223 766654

[email protected]

Dr Nicholas Walton

Institute of Astronomy

Cambridge University

Tel: +44 (0) 1223 337503

[email protected]

Media contacts

Dr Robert Massey

Royal Astronomical Society

Mobile: +44 (0) 7802 877699

[email protected]

Doctor Morgan Hollis

Royal Astronomical Society

Mobile: +44 (0) 7802 877700

[email protected]

Details of the scientific briefing

The new results will be presented in a special online briefing hosted by the Royal Astronomical Society, at 9:15 GMT on Thursday 3 December, with a dedicated press session at 1030 GMT.

Media members are cordially invited to attend. Register through Eventbrite. Zoom connection details will be sent to subscribers one hour before the meeting starts.

*** We highly recommend early registration for this webinar as numbers are limited ***

Images and movies

A diagram of the Milky Way’s two most important companion galaxies, the Large Magellanic Cloud or LMC (left) and the Small Magellanic Cloud (SMC) made using data from the European Space Agency’s Gaia satellite. The two galaxies are connected by a 75,000 light-year long bridge of stars, some of which extend from the left of the SMC.

Credit: ESA / Gaia / DPAC

Movie [available after the embargo expires]

Our sunny neighborhood

Since 2013, the European Space Agency’s Gaia satellite has measured the positions and characteristics of nearly two billion stars in our galaxy, the Milky Way. This film is an overview of the closest 326 light-years to the Sun, a region of space that contains some 300,000 stars.

Credit: ESA / Gaia / DPAC

The large and small clouds of Magellan

Data from the European Space Agency’s Gaia Space Observatory help us understand the different stellar populations in the Milky Way’s two main companion galaxies, the Large and Small Magellanic Clouds. This animation moves from an image of the Milky Way to the two systems, showing the separate populations of stars in each of them. It then illustrates the dramatic bridge of stars connecting LMC and SMC, which spans 75,000 light years.

Data sets provided by Merce Romero-Gomez. Video based on the article: Gaia Early Data Release 3: structure and properties of the Magellanic Clouds by Gaia Collaboration, X. Luri et al., A&A 2020 (in press).

Credit: ESA / Gaia / DPAC

Further information

The Gaia Early Data Release 3 will be available free of charge to the scientific community and the wider public after 1100 GMT on Thursday, December 3rd.

Institutes in the UK have played a pivotal role in a wide range of aspects of the new release of Gaia data. At the Royal Observatory in Edinburgh, supported by Leicester University, software for data preprocessing was prepared and tested; photometric data have been processed and prepared for publication at the Institute of Astronomy (IoA) in Cambridge, and work on software for processing the spectroscopic data produced by the mission is continuing at the Mullard Space Science Laboratory. UK activities in the Gaia project are supported by grants from the UK Space Agency and the Council for Scientific and Technological Facilities.