The European space telescope called Gaia, unveils on Thursday the first part of its catalog of celestial objects.

This is the third catalog of the telescope which is stationed 1.5 million kilometers from Earth.

A very important scientific contribution regarding the measurement of stars.

For the researcher, Chantal Panem, "the discoveries will multiply".

The European space telescope Gaia unveils Thursday the first part (EDR3) of a catalog of more than 1.8 billion celestial objects in our galaxy, observed with unparalleled precision.

The event is awaited by the thousands of scientists around the globe who dig daily into the data of the machine, put into orbit by the European Space Agency (ESA) in 2013. 

Gaia is stationed 1.5 million kilometers from Earth, opposite the direction of the sun, to better protect itself from its radiation.

Sheltered under a hood that shields the impacts of micrometeorites, its two optics sweep through space slowly, with a full turn in six hours.

The telescope detects and observes a very small part of the stars in our galaxy, which has a diameter of 100,000 light years, and beyond.

Its catalog lists a host of celestial objects, ranging from all known varieties of stars, exoplanets and asteroids, to the interstellar medium and galactic clouds close to our Milky Way.  

"A knowledge revolution"

These observations, detected by an assembly of photo cells of almost a gigapixel, make it possible to locate their position, distance and displacement.

With measurements of their physical characteristics, scientists can better understand the phenomena of formation and evolution of stars, and our galaxy. 

A new stellar census of 331 312 stars in our solar neighborhood has been obtained by @ESAGaia with 100x more stars & reaching 4x farther than Gliese Catalog of Nearby Stars.

Animation shows movement of 75k stars around our galaxy # GaiaEDR3https: //

- ESA Science (@esascience) December 3, 2020

After a first catalog in 2016, it is thanks to the second, delivered in 2018 with 1.7 billion sources, that scientists have determined for example that our Milky Way had "merged" with another galaxy, ten billion ago years.

It is therefore a third catalog which is unveiled Thursday.

Gaia has brought about "a revolution of knowledge", told AFP Catherine Turon, astronomer emeritus at the Paris-PSL Observatory, pioneer of space astrometry and involved in the mission from its inception.

One of these inter-galactic collisions "corresponds to the age of our solar system, leading to the hypothesis that with each collision there is an outbreak of star formation", of which our sun would be a part.

"The discoveries will multiply," said Chantal Panem, head of mission at the National Center for Space Studies (CNES), noting that "about 3,800 scientific articles using Gaia data have been published" since second catalog.

A very precise measurement of the stars

The third enriches the previous ones, with 1.8 billion celestial objects, and "above all much better astrometric and photometric precision", according to Catherine Turon.

The measurement of the displacement of stars is two to three times more precise, and the calculation of their distance has been improved by about 30% compared to the previous catalog.

Progress due in large part to the accumulation of data studied, over 34 months of observation, against 22 for the second catalog.

Until the 1990s, the position of barely 8,000 stars could be determined from Earth using an angle measurement, the parallax method.

Gaia's precursor, Hipparcos, has revolutionized the field since its launch by ESA in 1997, cataloging more than 110,000 celestial objects.

Gaia has a thousand times greater measurement accuracy.

This extreme precision has a downside: the volumes of data to "swallow" and process are ever greater.

To date, Gaia has transmitted over 80,000 billion bytes.

A volume which mobilizes a large IT platform of CNES in France, and those of European partners.

And which explains why it took more than three years to manufacture and validate this first part of the catalog, "which includes the positions, distances, movement and magnitude of the stars", explains Catherine Turon.

"No final catalog before 2028"

The second part, with for example data on the physical characters of the observed objects, the classification of variable stars, and data on the Andromeda galaxy, will be available in the first half of 2022. The end of Gaia's mission is now scheduled for 2025. "We will not have a final catalog before 2028, at best", says Chantal Panem.

Until then, we can expect major discoveries, according to Catherine Turon, with "for example the exhaustive census of all the massive exoplanets all around the solar neighborhood".

The general public is invited to a conference Thursday evening at 9:00 p.m. to find out more, it's here.