A treasure: diving into the figures of the 3rd catalog of the Gaia telescope


Eric Bottlaender

Space specialist

June 14, 2022 at 9:30 a.m.

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Gaia DR3 milky way general © ESA/Gaia

The Milky Way and different characteristics of its stars and its dust highlighted by the study of data from Gaia. Credits: ESA/gaia

In a gargantuan avalanche of data, the third catalog of the Gaia space telescope of the ESA is available since June 13 at noon. A vertiginous dive into this astrometry mission which continues to revolutionize the data of the Solar System, our galaxy and the Universe.

50 scientific publications were published in the process.

Behind the scenes of the Data Release

Sent into space at the end of 2013, the Gaia space telescope collects its data from the Earth-Sun Lagrange Point L2 (like its cousin the James Webb). By recording with unprecedented precision the position of the objects it observes as well as the characteristics of their light, Gaia sends data centers around 50 GB of positions and characteristics every day.

Teams from 19 countries form the DPAC (Data Processing and Analysis Consortium), which publishes at different intervals Gaia’s data catalogs, grouping the measurements. Each catalog is more extensive than the previous one, because Gaia observes the same objects several times with longer time intervals, refining the position, luminosity, speed, composition data…

Gaia DR3 star composition © ESA/Gaia/DPAC

Example of a study published directly with the publication of the DR3 catalog, indicating the analytical composition of millions of stars in the galactic disk. Credits: ESA/Gaia/DPAC

Do you already see what a million that is, Larmina?

A gigantic catalog of 2 billion objects in the sky, mainly stars, but also asteroids and galaxies. And again, DR3 concerns “only” the period of the first 34 months of mission, until May 28, 2017. It must therefore be kept in mind that there will still be a fabulous mine of data to be exploited now that the catalog DR3 is released.

The numbers, however, are already making your head spin. 1.8 billion stars identified in our area of ​​the Milky Way, including 1.5 billion classifications (type of stars) and as many positions and luminosities. 34 million stars whose radial velocity is known (their displacement relative to ours), 10 million variable stars, 220 million detailed spectra with temperature, mass, age, color, metallicity… And data on 813,000 stars binaries, including their type, their respective mass and their orbits. A documentation so extensive that it will provide statistical study data for decades, but also targets for long observation campaigns from Earth or other specialized space telescopes.

The luminosity data on the stars, being studied in a very fine way, also communicate new information on the space between them, the interstellar medium. Which is far from empty: Gaia has made it possible to draw up a 3D map of the clumps of dust and gas in our Milky Way. Enough to study the “nurseries of stars”, but also to understand what molecules are composed of these gases and dust. By analyzing 470 million light spectra of stars, the teams have isolated the characteristics of interstellar dust… But also learned a lot from the stars themselves. A true stellar CV for millions of them, with up to 42 different parameters.


Closer or farther than the stars

Haven’t the stars made you dizzy yet? The DR3 catalog focuses on two other points at different scales. The first is asteroids. Indeed, with its instruments designed to detect the lowest possible star luminosity, Gaia regularly captures them. That it is then possible to categorize, then to find and classify. And there again, the figures are at the usual scale of the telescope: industrial. 156,000 asteroids detected, from almost all known families: near-Earth cruisers, those in the asteroid belt, trans-Neptuneans, etc. We find their position, their orbit, whether they have a small moon or not, and even clues to their composition and shape, thanks to the characteristics of the light reflected from their surface.

Similarly, Gaia has categorized objects much more distant than the Milky Way: 6.6 million candidate Quasars, and nearly 5 million galaxies, 2.9 of which are characterized with their luminosity, shape, color, and for some the age of their stars!

Us, and billions of stars. Credits: ESA/Gaia/DPAC

Servers need to keep…

The discoveries will be legion for the scientific teams who will look in detail at the data. There are already nuggets in publication, such as the identification of stars resulting from collisions between small galaxies and the Milky Way by their age and their composition. The list is long and the uses varied. For example, a team has analyzed 5,863 stars analogous to our Sun (ten times more than previously known) to understand its past, and study the ways in which it will evolve in the future. From the rotational speed of stars in the Milky Way to the orbit and mass ratio of hundreds of thousands of binary stars, the catalog (open to everyone) offers a new perspective on the objects that make up our universe.

There are at least two future DR4 and DR5 catalogs to be published by 2025 and 2030. These will further refine the measurements and expand the number of characterized stars. There will be other specific focuses, notably for DR4 the subject of exoplanets. Even if Gaia is not designed for that, its performance over the long term should still make it possible to identify more… than ten thousand candidates. Figures that have not finished fascinating, especially since ESA teams are already thinking about the design of a possible successor for the end of the next decade. The map of our universe has not finished getting richer.

On the same subject :
The James Webb Telescope will study 55 Cancri e, a lava-covered exoplanet

Source : ESA, Gaia



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