The European Space Agency has just released the latest data from its Gaia mission, detailing the physical characteristics and positioning of nearly 1.8 billion stars in our galaxy. The movements of stellar sources in the periphery also testify to the turbulent past of the Milky Way.
A map of the Milky Way
At the end of 2013 the European Space Agency (ESA) lapped Gaia, a satellite aimed at determining the position, movement and distance of stars in our galaxy in addition to their physical properties. To do this, Gaia operates in an orbit around the point of Lagrange 2 (L2), located 1.5 million kilometers behind the Earth in the direction opposite to the Sun. The gravitational forces between the Earth and the Sun are balanced there, so that the spacecraft remains in a stable position.
From this position, Gaia continuously scans the sky, collecting data in several bands of the light spectrum and recording data for several thousand stars every day. FYI, the satellite’s billion-pixel camera is the largest ever sent into space. The instrument is indeed so powerful that it would be able to assess the diameter of a human hair at a distance of a thousand kilometers.
The latest catalog, published in April 2018, offered us the characteristics of nearly 1.7 billion stars. The new catalog (Gaia EDR3) released this Thursday, December 3 contains detailed information about an additional one hundred million stellar sources. Among them, 300,000 evolve within 326 light years of the Sun. In addition to including more sources, the accuracy of the measurements has also improved.
Traces of an ancient collision and an accelerating Solar System
The new data from Gaia has enabled astronomers to trace the different populations of stars moving towards the very edge of our galaxy, the galactic anticenter.
These data revealed a component of slowly moving stars above the plane of our galaxy and heading in its direction, as well as a component of fast-moving stars this time moving below the plane and moving upwards. . “This extraordinary model was not foreseen before,” emphasizes ESA. “This could be the result of the virtual collision between the Milky Way and the dwarf galaxy of Sagittarius operated in the recent past of our galaxy”.
As a reminder, the dwarf galaxy of Sagittarius is currently being “cannibalized” by the Milky Way. Its last close passage to our galaxy, to which the press release refers, was not enough to disintegrate it, but the blow was obviously violent enough to disrupt some stars in the Milky Way.
Finally, data from Gaia also confirmed the acceleration of the Solar System around the galactic center. This acceleration is gentle, but enough to deviate the trajectory of our system by an atom in diameter every second. In one year, this represents approximately 115 km. Fear not, this first measurement of the curvature of the Solar System’s orbit around the galaxy is consistent with theoretical expectations. In other words, it’s normal.