A space telescope that observes the stars in the Milky Way as they appear today reveals what happened to the galaxy when it was only a few billion years old, and the upcoming release will allow astronomers to glimpse into the even more distant past.
of the European Space Agency Gaia’s mission is not a common name like Hubble Space Telescope or James Webb Space Telescope. And yet the mission currently produces the most scientific articles and, like Milky Way researchers would tell you has allowed unprecedented leaps in our understanding of the history of the galaxy.
Gaia works differently than Webb or Hubble. Instead of watching The universe one fascinating distant object at once, Gaia scans the whole sky over and over again. The telescope, like a flying saucer, nestled inside Lagrange point 2 about 930,000 miles (1.5 million kilometers) from Earth, watching 2 billion of the brightest stars in the sky, its appearance is free from the distorting effects of Earth’s atmosphere that it affects the observations of ground-based telescopes.
Connected: 4 great mysteries of the Milky Way that Gaia’s next mission can solve
Unlike Hubble and Webb, Gaia does not focus on capturing impressive images that reveal every detail of these distant stars and galaxies. Instead, the probe focuses on several basic parameters: the distance of the stars from The Earththe speed at which the stars move in space, and the direction of their movement, as it appears in the plane of the sky and in three dimensions.
As objects in space follow laws of physics, scientists can model the trajectories of these stars billions of years in the past and future, revealing the events that shaped the evolution of the galaxy. A discipline known as galactic archeology has grown tremendously since the launch of Gaia in 2013, and new data release on Monday (June 13th) is set to boost research.
“We are still trying to figure out the details of the origin of the Milky Way,” Anthony Brown, an astronomer at Leiden University in the Netherlands and chairman of the Gaia Data Processing and Analysis Consortium, told Space.com. “With the new version, we should be able to do it even better because we’re getting new data.”
The trajectories of the stars in the Milky Way galaxy over the next 400,000 years based on measurements from the European Gaia mission. (Image Credit: ESA / Gaia / DPAC)
Getting to know the stars
These new data contain what astronomers call astrophysical parameters. Derived from the light spectra of observed stars (essentially the imprints of how stars absorb light), astrophysical parameters reveal age, mass, brightness levels, and in some cases the detailed chemical composition of observed stars.
“You really know the stars,” Jos de Bruijne, a scientist at Gaia’s ESA project, told Space.com. “It’s like you have an anonymous group of people and now you can meet each of them. You’ll learn their names, how old they are and where they came from.”
The group of stars that astronomers are “meeting” with, thanks to published data from June 13, consists of half a billion individual objects, a quarter of the stars that Gaia observes. This information will help astronomers to refine the order of events that shaped the Milky Way and “really unravel the history of its formation,” added Brown.
The Milky Way absorbs small galaxies in its orbit. (Image Credit: ESA / Gaia / DPAC)
What we already know
Astronomers believe that the Milky Way began to form only about 800 million years later Big bang and went through a period of 1 billion to 2 billion years of intense formation, Brown said. This period of formation includes many collisions with other galaxies that are gradually building the Milky Way to what we see today: massive spiral galaxy covers 200 billion stars. (Gaia sees only about 1% of them.)
In previously published data on Gaia, researchers found traces of these early collisions in the form of waves that are still moving through the galaxy, affecting the movement of stars. The most significant of these collisions was with a galaxy called Gaia Enceladus. This galaxy was about four times smaller than the Milky Way when the two crashed about 10 billion years ago. The collision, Gaia’s data revealed, led to the halo of the Milky Way, a sphere of thinly scattered stars enveloping the galaxy’s much more massive disk.
“It simply came to our notice then [the collision with Gaia Enceladus] it was the last significant merger that the Milky Way underwent, “Brown said.
(Image credit: ESA)
Tracking the “smallest building blocks”
Among the astronomers awaiting the release on June 13 is Eduardo Balbino, a postdoctoral fellow in astrophysics at the University of Groningen in the Netherlands. Balbino is interested in more modest collisions with what he calls the “smallest building blocks” of the galaxy: spherical clustersancient groups of stars swallowed by the Milky Way through the eons.
“[The globular clusters] are special because when they dissolve into these cumulative events, they break, “Balbino said.” But they continue to live as coherent groups of stars in the sky, as we call them. stellar flows“
These stellar streams are extremely difficult to detect, but Balbino believes that new data from Gaia will lead to a breakthrough in this endeavor.
“There will be an additional component of speed [in the new data set], the so-called radial velocity – how fast the stars move towards or far from us, “said Balbino.” Gaia has measured some of these before, but the new sample will be 10 times larger. It’s bigger than anything before. “
In these motions of stars, astronomers will be able to distinguish groups of stars that move through the galaxy in sync. By combining this information with data on the chemical composition of stars (stars from other galaxies have different chemical profiles), astronomers will be able to look into the galaxy’s past like never before.
“This is one of the exciting things you can do with Gaia data,” Balbinot said. “You can find these groups of stars that move in a similar way and basically reconstruct where they came from and what building block brought them to the Milky Way. Then you can finally answer the question of how the Milky Way came to be.”
What is happening on the edge of the galaxy
Balbino hopes the new data will allow astronomers to search for the remains of globular clusters far farther from Earth than was previously possible, on the very outskirts of the galaxy, where the galactic halo meets intergalactic space.
“The new data set will contain a small amount of data on variable stars that are very bright, and because they are so bright, we can see them all the way to the edge of the Milky Way,” Balbinot said. “They’re essentially the most distant stars we’ll ever be able to find in our Milky Way galaxy. And that’s really exciting because it’s really unexplored territory.”
Balbino said the changing stars could reveal remnants of ancient collisions with globular clusters scattered throughout the galactic halo in the form of spherical “shells.” An analysis of these shells can reveal much about the anatomy of the events that gave rise to them billions of years ago.
“There are many things you can conclude from measuring the distance of these shells,” Balbinot said. “You can reconstruct how these accumulation events happened in detail, what is the orbit of the satellite [galaxy] which fell into the Milky Way and so on. “
Looking to the future
The last few billion years have been quite peaceful for the Milky Way. The galaxy ejects stars and sees them die at a constant rate while still absorbing aftershocks from earlier shakes.
But in the future, things will get tough again. In fact, astronomers are already watching the approach of the next galactic collision: the collision with two dwarf galaxies in the orbit of the Milky Way, called Large Magellanic cloud and on Small Magellanic cloud.
“Magellanic clouds have entered orbit around the Milky Way relatively recently, over the last few billion years,” Brown said. “We can already see that they are influencing the gravitational field of the Milky Way, and if we reconstruct the past really well, we may be able to push everything forward and see when the clouds will merge with the Milky Way.”
Despite the turbulent childhood of the Milky Way, the most cataclysmic event is yet to come: the collision with Andromeda Galaxythe nearest large galactic neighbor.
Andromeda, currently over 2.5 million light years from Earth, is among the celestial objects that Gaia observes. The new release will provide a new insight into the meeting, which will shake the two galaxies in about 4.5 billion years.
With Gaia, “you can pretty well measure the movement of the Andromeda Galaxy through the line of sight,” Brown said. “This puts more constraints on the long-term future of the two galaxies.”
IN the sun will be near the end of her life when her mother galaxy meets Andromeda, so humanity is unlikely to still exist to witness the galactic crash. The earth will surely be uninhabited long ago, scorched by the scorching sun.
Still, unraveling the galaxy’s past and future is a compelling project that will last for many years as Gaia produces more and more data.
The telescope will retire in 2025, when it runs out of fuel. But it has certainly not passed its peak, De Bruyne said. The consortium of 400 researchers processing Gaia’s data is still refining the algorithms used to analyze the vast amounts of measurements the telescope produces. These algorithms allow astronomers to find ever finer details and new types of information in a vast array of data. The June 13 issue, for example, will feature the largest catalog of chemical formulations to date asteroids in the solar system and the largest data set to date binary star systems. The next edition of Gaia’s data will already reveal thousands of new ones exoplanetssaid De Bruyne.
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