The Gaia space observatory continues to redesign and color the map of our galaxy. L’European Space Agency (ESA) today published a new release of data: from the largest catalog ever compiled, which contains nearly two billion stars, a mosaic of great scientific value takes shape. The ESA mission, in fact, not only observed and traced the orbits of hundreds of millions of luminous dots in the dark of the night, but its vision proved to be sharp enough to ‘see’ the earthquakes that shake the stellar surface, to give the hunting for asteroids in our solar system, even spying on distant quasars and galaxies.
Results that will be useful to a large part of the scientific community that studies the evolution of the Cosmos, from our neighborhood to the most remote distances: “It is a gold mine – underlines Antonella Vallerani, INAF astrophysicist at the Padua Observatory and deputy coordinator of the of the Gaia Data Processing and Analysis Consortium – with this third data release we expect sensational scientific results “. The mission sees a strong participation of the Italian Space Agency (ASI) and the National Institute of Astrophysics (INAF).
The 3D map of the Milky Way
Launched in 2013, the ESA probe has the task of making the largest census of stars, scanning the entire sky in every direction. At the bottom of the Gaia well over one billion and 800 million have ended up. He gave us back the exact position of each but, above all, he was able to describe how it moves in space. In previous publications (the latest in 2020) he had already amazed us by showing us what the sky will be seen from Earth in millions of years, due to the motion of the stars that will change the shape of the constellations. Now she has gone further. “I think one of the biggest news is that of radial speed – he explains to Italian Tech Timo Prusti, of ESA, project manager of the Gaia mission – that is, the speed of objects coming towards us or moving away. Now we also know how stars move in three-dimensional space ”.
The largest atlas of the stars in 3D. According to Gaia
by MATTEO MARINI
The probe is located one and a half million kilometers from Earth, an advantageous point for observing, without disturbing the atmosphere. Gaia has two telescopes with which she has made billions of observations. In fact, it is not enough to take a “picture”, but you have to repeat the observations over time as frames of a movie, to see how everything moves around us. The probe spins on itself every six hours, and scans the entire sky every
six months. It is able to capture the light of stars millions of times fainter than the faintest star visible to the naked eye, but it can also go “to the essence”.
The DNA of the stars
The light that comes from a source (even from the Sun) carries with it a kind of fingerprint, in its spectrum scientists see absorption lines left by the elements that make up the star. Gaia thus put pen to paper the composition of two and a half million stars, as if it were a genetic code: “This has a great impact on the study of our galaxy – says Vallenari, who has followed the project for over thirty years, since its conception – because it allowed us to take a ‘family photo ‘. See which are the oldest and youngest stars and the chemical component: it tells us the gases from which they formed, and therefore where they formed. Whether within the Milky Way or in external galaxies which then ‘fell’ into ours. From this and their movement we can reconstruct their family tree “.
We know for example that many of the stars that together with us revolve around the center of the Milky Way belonged to a galaxy that in a remote time was engulfed by ours. We recognize them from their chemical composition but also from the fact that they move differently: “It is like looking at the people in the square from the top of the Milan Cathedral and then seeing a group of Carabinieri on horseback enter. They stand out because they move differently ”adds Vallenari.
Old stars and young stars
Immediately after the Big Bang there was hydrogen, helium and little else. The first stars had nothing else to light up and burn. It has been a long way, that of these recombinant nuclear furnaces of matter, to form heavier elements. Iron, calcium, magnesium and carbon (the “metals”), the same of which we are made and much of what surrounds us here on Earth, were forged in the heart of the stars to then be expelled, released into space even in the gigantic supernova explosions.
From this new material new stars are born but also planets, like ours: “We can look at these generations of very old stars that had little iron and distinguish them from the younger ones, like the Sun, which have more” observes Prusti.
Thanks to Gaia, it was discovered how they are distributed: “We have to think of our galaxy as a plate, the disk, with a ball in the center, which is the bulb, inside which there is the black hole. And all around a large diffuse cloud of stars which is the halo – the Inaf astrophysics recalls – the youngest stars are almost all found in the disk, because there are gases there, and where there is a lot of gas stars are formed , together with a part of very ancient ones, of
about 10 billion years. The central part is very complicated, there are ancient stars and star-forming regions. In the outer halo, however, there are only old stars “.
Earthquakes on the surface of the stars
According to the researchers, one of the most surprising results concerns what have been called “stellar earthquakes”. Tsunami-like vibrations that shake the surface. A proof of the fineness of detail that Gaia is able to achieve: “A bit like for the Earth, the seismic waves allow us to see what is underground. We have seen those of earthquakes inside the stars because their light changes – highlights Vallenari – a phenomenon that was known but that we have also found in stars from which we did not expect it. This makes us rewrite the star models ”.
Asteroids and quasars
In the basket of light of Gaia everything is really finished. You have “characterized” by mass and evolution 800 thousand binary stars, which revolve around each other as in a circle. But she also sifted through the solar system, because asteroids enter her field of vision as well. It has recognized about 156 thousand of them, drawing their trajectory in a very precise way, and from their light he was also able to recognize the color and which elements they are composed of. So as to help us learn more about the origins of our solar system: “This allowed us to identify families of asteroids, of the same composition, which then formed together. Perhaps even from a single large celestial body – reflects the teacher – and with such precise orbits, in the future, we will also be able to better define their possible danger “.
Finally, Gaia collected information on macro molecules dispersed in the gas in the interstellar medium. It has emerged in the empty space around our Solar System that there are gases that contain carbon compounds. Going far, he observed millions of galaxies and quasars, nuclei of active galaxies and which are the brightest objects in the Universe. “The Gaia data processing and data analysis consortium involves about 450 people – concludes Prusti. In the past years, from previous publications, about 1,600 scientific studies every year, we expect this to continue because the real surprise was the large amount of things that Gaia saw. There really is something for everyone ”.