of the European Space Agency Gaia mission is not a familiar name like Hubble Space Telescope or the James Webb Space Telescope. However, the mission is currently producing most of the scientific work and, as such Galaxy researchers will tell you, has allowed unprecedented leaps in our understanding of the history of the galaxy. Gaia works differently than Webb or Hubble. Instead of noticing the universe one fascinating distant object each time, Gaia sweeps across the sky over and over again. The telescope that looks like a flying saucer, nestled inside Lagrange point 2 approximately 930,000 miles (1.5 million kilometers) from Earth, observing 2 billion of the brightest stars in the sky, its view free from its distorting effects Earth’s atmosphere plaguing telescope observations. Unlike Hubble and Webb, Gaia does not focus on capturing awe-inspiring images that reveal every detail of these distant stars, and galaxies. Instead, the detector focuses on a few key parameters: the distance of the stars from Earththe speed at which the stars move in space and the direction of their motion as shown in the sky and in three dimensions. Because objects in space follow laws of physics, scientists can model the orbits of these billion-year-old stars past and future by sorting out the events that shaped the evolution of the galaxy. An industry known as galactic archeology has grown exponentially since the launch of Gaia in 2013, and new data releases coming out on Monday (June 13th) are set to boost research. “We are still trying to find out the details of the origin of our galaxy,” Anthony Brown, an astronomer at the University of Leiden in the Netherlands and chairman of the Gaia Data Processing and Analysis Consortium, told Space.com. “With the new release, we should be able to do it even better, because we are getting some new data.”
Star orbits in the galaxy over the next 400,000 years based on measurements by the European mission Gaia. (Image credit: ESA / Gaia / DPAC)
Acquaintance with the stars
This new data contains what astronomers call astrophysical parameters. Derived from the light spectra of the observed stars (essentially the fingerprints of the way the stars absorb light), the astrophysical parameters reveal ages, masses, luminosity levels and, in some cases, detailed chemical compositions of the observed stars. “You really know the stars,” Jos de Bruijne, a Gaia scientist at ESA, told Space.com. “It’s like having an anonymous group of people and now you can meet each one of them. You know their names and how old they are and where they come from.” The group of stars that astronomers “meet” thanks to the release of data on June 13 consists of half a billion individual objects, a quarter of the stars observed by Gaia. This information will help astronomers improve the sequence of events that shaped our galaxy and “really unravel the history of its formation,” Brown added.
The Galaxy devours small galaxies in its orbit. (Image credit: ESA / Gaia / DPAC)
What we already know
Astronomers believe that the galaxy began to form only about 800 million years later Big explosion and went through a period of intense formation of 1 to 2 billion years, Brown said. This period of formation involved many collisions with other galaxies, which gradually created the Galaxy in what we see today: a huge spiral galaxy which includes 200 billion stars. (Gaia sees only about 1% of them.) In previously released Gaia data, researchers have found traces of these early collisions in the form of waves that continue to wave within the galaxy, affecting the movement of stars. The most important of these collisions was with a galaxy called Gaia Egelados. This galaxy was about four times smaller than the Galaxy when the two crashed about 10 billion years ago. The collision, as revealed by Gaia data, created the halo of the Galaxy, the sphere of finely scattered stars that surrounds the galaxy’s much larger mass. “It simply came to our notice then [the collision with Gaia Enceladus] “It was the last major merger the Galaxy underwent,” Brown said.
(Image: ESA)
Detecting the “smallest building blocks”
Among the astronomers awaiting the June 13 release is Eduardo Balbinot, a postdoctoral researcher in astrophysics at the University of Groningen in the Netherlands. Balbinot is interested in more modest collisions with what he calls the “smaller structural elements” of the galaxy: spherical swarmsancient star clusters devoured by the Galaxy over the centuries. “[The globular clusters] “They are special, because when they disintegrate in these incremental events, they disintegrate,” Balbinot said. “But they continue to live as cohesive clusters of stars in the sky as we call them stellar streams. “ These stellar currents were very difficult to detect, but Balbinot believes that Gaia’s new data will lead to a breakthrough in this endeavor. “There will be an additional speed component [in the new data set], the so-called radial velocity – how fast the stars move towards or away from us, “said Balbinot. “Gaia has measured some of these before, but the new sample will be 10 times larger. “It’s bigger than anything before.” In these star movements, astronomers will be able to distinguish groups of stars moving synchronously across the galaxy. By combining this information with data on the chemical composition of stars (stars that arrived from other galaxies have separate chemical profiles), astronomers will be able to look at the galaxy’s past like never before. “This is one of the most exciting things you can do with Gaia data,” said Balbinot. “You can find these groups of stars moving similarly and basically reconstructing where they came from and what structural element brought them to our Galaxy. Then, you can finally answer the question of how the Galaxy formed.”
What’s happening on the edge of the galaxy
Balbinot hopes the new data will allow astronomers to search for remnants of spherical clusters farther away from Earth than was previously possible on the periphery of the galaxy, where the galaxy halo meets intergalactic space. “The new data set will contain a small subset of data for variable stars, which are very bright, and because they are so bright, we can see them all the way to the edge of our galaxy,” Balbinot said. “They are basically the most distant stars we will ever be able to detect in our galaxy. And that’s really exciting, because it’s really an uncharted area.” Balbinot said the variable stars could reveal remnants of ancient collisions with spherical clusters scattered across the galaxy halo, in the form of spherical “shells.” Analysis of these shells can reveal much about the anatomy of events that caused them billions of years ago. “There are a lot of things you can deduce from measuring the distance of these shells,” Balbinot said. “You can reconstruct how these augmentation events happened in detail, what the orbit of the satellite was [galaxy] which fell into the Galaxy and so on. “
Looking to the future
The last billions of years have been quite peaceful for the Galaxy. The galaxy stirs stars and sees them die at a steady rate while absorbing the aftershocks of previous upheavals.
But things will get tough again in the future. In fact, astronomers are already observing the approach of the next galactic collision: the crash of two dwarf galaxies into the orbit of a galaxy called Great Magellanic Cloud and Small cloud of Magellan.
“Magellanic clouds have been orbiting the galaxy quite recently, for the last billions of years,” Brown said. “We already see them influencing the gravitational field of our galaxy, and if we reconstruct the past very well, we may be able to move forward and see when the clouds will merge with our galaxy.”
Despite Milky Way’s violent childhood, the most cataclysmic event still lies ahead: the collision with the The Andromeda Galaxythe nearest large galactic neighbor.
Andromeda, currently over 2.5 million light years from Earth, is one of the celestial objects that Gaia observes. The new data release will give a new picture of the meeting that will rattle the two galaxies in about 4.5 billion years from now.
With Gaia, “you can really really measure the Andromeda Galaxy’s motion across the line of sight,” Brown said. “This gives you more restrictions on the long-term future of the two galaxies.”
The sun will be near the end of his life when his native galaxy meets Andromeda, so humanity is unlikely to still exist to watch the galactic crash. The Earth, for sure, would have been uninhabited for a long time, burned by the increasingly hot sun.
However, unraveling the galaxy’s past and future is a fascinating task, which will continue for several years as Gaia produces more and more data.
The telescope will be withdrawn in 2025, when it will run out of fuel. But it has certainly not reached its peak, De Bruijne said. The consortium of 400 researchers processing Gaia data continues to improve the algorithms used to analyze the enormous amount of measurements produced by the telescope. These algorithms allow astronomers to find finer details and new types of information in the vast body of data. The June 13 release will contain, for example, its largest list of chemical compositions asteroids in the solar system and the largest data set binary star systems. The next release of Gaia data is already going to reveal thousands of news exoplanetssaid De Bruine.
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