"The Gaia mission is more productive than the Hubble Space Telescope"

The Gaia satellite, cartographer of the Milky Way

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NarrativeThe satellite launched in 2013 has just delivered to the scientific community a first version of a three-dimensional map of approximately 1% of the Milky Way. A major advance in astrometry.

It is the height from which one embraces the landscape. The tree that dominates the forest… The third delivery of the Gaia space astrometry mission marks a new turning point in the study of the composition, formation and evolution of our galaxy.

This European Space Agency (ESA) satellite, launched in 2013, systematically analyzes light from the brightest objects in the sky to produce a three-dimensional map of about 1% of the Milky Way. On June 13, it took a decisive step by delivering the first complete version of its catalog to the scientific community. In total, 1.8 billion stars and millions of other bodies, of which he managed to identify, not only the location on the celestial vault and the distance, but, also, for a certain number of them , speed or physical properties.

Read also: Article reserved for our subscribers Space: “The Gaia mission is more productive than the Hubble Space Telescope”

Such a survey far exceeds in importance all that has been done in the field of astrometry, the branch of astronomy devoted to measuring the position and movement of the stars. “The previous inventory, that of the ESA’s Hipparcos mission, between 1989 and 1993, had barely covered 120,000 of the 200 billion stars in our galaxy”recalls François Mignard, scientific manager of Gaia France.

It is also a real tour de force. To succeed in positioning objects on the celestial vault with a precision of 7 to 30 microseconds of arc, equivalent to the angle under which the thickness of a hair would be seen at 1,000 kilometers, Gaia, a satellite designed and produced under the contracting authority of Astrium (the former name of the space systems branch of Airbus-DS), scanned the sky with its two telescopes coupled to a set of ultra-sensitive CCD detectors for thirty-four months.

During this period, he analyzed, using his three instruments – astronomical, spectrophotometric and spectroscopic – no less than seventy times the light from each source, collecting a quantity of information of the order of several petabytes, unique in the history of astronomy. Once on Earth, this massive amount of raw data, comparable only to that produced (over a single year) by the LHC particle physics experiments at CERN, Geneva, was processed in six computing centres, including the one is located at the National Center for Space Studies (CNES) in Toulouse; then classified, stripped and formatted within a European consortium bringing together 430 scientists, including a hundred French.

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