The European Space Agency’s Gaia mission will release new data on June 13, and scientists can’t wait.
The next data dump will contain information about nearly two billion of the brightest objects in the sky. The launch will supercharge the mapping of our Milky Way galaxy, experts say, allowing astronomers to see the galaxy’s farthest fringes and also discern far finer details in its structure than ever before.
Gaia has mapped our stellar neighborhood since 2014, and each of its data rolls has led to giant leaps in our understanding of the universe. Milky Way. Astronomers have learned about the precise positions of large numbers of starstheir distances from Earth and the speeds at which they travel.
Thanks to years of obediently scanning Gaia’s sky, information about the trajectories and movements of stars in three-dimensional space is becoming increasingly accurate. Gradually finer details of the structure of the galaxy appear before the eyes of astronomers, and the story of their evolution comes to life.
The next release will add some previously unavailable information, including about the chemical compositions, ages and masses of millions of stars.
Related: 4 Big Milky Way Mysteries That Gaia Mission’s Next Data Dump Could Solve
more refined details
Among the astronomers eagerly awaiting the June 13 launch is Eduardo Balbinot, a postdoctoral researcher in astrophysics at the University of Groningen in the Netherlands. Balbinot is interested in globular clustersclusters of stars that are the “smallest building blocks of galaxies”.
Many globular clusters merged with the Milky Way billions of years ago after being drawn into its orbit by the galaxy. gravitational attraction. But even today, astronomers can distinguish its remains among the stars.
“Globular clusters are special because they separate [when they fall into the galaxy]but they still live as coherent groups of stars in the sky like stellar streams,” Balbinot told Space.com.
Balbinot is particularly eager to investigate a large set of measurements of radial velocities, the movement of stars away from or towards the observer. Obtaining these measurements is not an easy task, because the stars tend to be so far apart that the difference measured by Gaia over mere years of human time is barely noticeable. Still, the telescope, following the Earth in its orbit around the Sun in Lagrangian Point 2 (the same region where the The James Webb Space Telescope is), is getting better at the task. It is from these radial velocities that Balbinot and his colleagues hope to reconstruct the Milky Way’s finest structure.
“The radial velocity sample will be larger by a factor of 10 than what was available before,” said Balbinot. “And that’s really exciting. You can find these groups of stars that move in a similar way and basically reconstruct where they came from.”
a living map
Gaia data allows astronomers to do more than just map the Milky Way as it is today. As objects in space follow the rules of physics, the data allows modeling the trajectories of stars millions, or even billions, of years in the past and into the future. The result is a three-dimensional film of the galaxy’s evolution that is becoming increasingly thin and accurate, and that stretches back into the past.
The new data release will inject some color into this map as it contains information about astrophysical parameters of nearly half a billion stars. Astrophysical parameters, derived from the light spectra of stars (essentially fingerprints of how stars absorb light), reveal information about the masses, ages, temperatures and brightness levels of stars.
For two million stars, Gaia also measured chemical compositions of stellar atmospheres, which reflect the compositions of the molecular clouds in which these stars were born billions of years ago.
By combining information about chemical compositions with the trajectories of stars reconstructed from Gaia’s measurements, astronomers can trace stars back to their birthplaces. They can not only identify where in the Milky Way each group of stars formed, but also identify those that arrived from elsewhere. (The Milky Way as we see it today emerged from collisions with other smaller galaxies. The stars that came from these other galaxies have a unique chemical fingerprint.)
“One of the interesting things you can do with Gaia is that 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 into our Milky Way,” Balbinot said. “Ultimately, [you can] answer the question of how the Milky Way was formed.”
The elusive spiral structure
Two billion stars may seem like a lot, but it’s actually only about 1% of the expected number of stars in the Milky Way. Thanks to sophisticated algorithms and a lot of scientific knowledge, astronomers can extrapolate what they learned from Gaia to better understand the galaxy as a whole. One of the outstanding issues they hope to learn more about is the The Milky Way’s trademark spiral structure.
Most astronomers agree that the Milky Way has four spiral arms, the dense tortuous streams of stars and gas that appear to emanate from the center of the galaxy. But there are some points of contention around these spiral arms. Astronomers still debate the size and prominence of the individual arms, as well as their exact position in the Milky Way’s disk. The new data may help reveal the spiral structure more clearly.
“With the astrophysical parameters we have now, we can directly sample stars for specific scientific cases,” Jos de Bruijne, Gaia project scientist at the European Space Agency, told Space.com. “We know that spiral arms are mostly made of young stars. It’s where stars form. So with the new data, we can look, for example, at stars that are no more than 100 million years old.” (100 million years is childhood in stellar terms. Our own sun is 4.6 billion years old and still has five billion years to go.)
Balbinot said the new dataset will reveal information about stars much further away from Earth than those from previous Gaia releases. Some of these stars are at the edge of the Milky Way, where the so-called galactic halothe diffuse sphere of stars scattered around the galaxy’s much more massive disk meets intergalactic space.
“These are variable stars, very bright stars that vary in brightness over time,” said Balbinot. “Because of their brightness, we can detect them even very far away. Some of these stars are on the edge of the Milky Way, and that’s very exciting because this is really uncharted territory. Everything we find there will be new and exciting.”
In these far reaches of the galaxy, Balbinot hopes to find evidence of older galactic collisions and distinguish structures that emerged from them.
“These collisions leave all kinds of debris behind,” he said. “Sometimes it’s stellar currents, but sometimes they can create shells, spherical features in the Milky Way’s halo. I think with these variable stars, we might be able to pick up some of those shells in the outer halo. And that would help to reconstruct in detail how those collisions happened.”