The European Space Agency’s Gaia mission will release new data on June 13, and scientists can’t wait.
The upcoming data dump will contain information on nearly two billion of the brightest objects in the sky. Experts say the release will boost the mapping of our galaxy, the Milky Way, allowing astronomers to see to the farthest reaches of the galaxy and discern much finer detail in its structure than ever before.
Gaia has been mapping our stellar neighborhood since 2014, and each of its data releases has led to giant leaps in our understanding of the Milky Way. Astronomers have learned the precise positions of a large number of starstheir distance from Earth and the speeds at which they move.
Thanks to years of conscientious observation of the sky by Gaia, information about the trajectories and movements of stars in three-dimensional space is becoming more and more precise. Gradually, finer details of the structure of the galaxy loom before the eyes of astronomers, and the story of its evolution comes to life.
The next release will add previously unavailable information, including the chemical compositions, ages and masses of millions of stars.
Related: 4 big Milky Way mysteries the next Gaia mission data dump could solve
Among the astronomers eagerly awaiting the June 13 publication is Eduardo Balbinot, a postdoctoral researcher in astrophysics at the University of Groningen in the Netherlands. Balbinot is interested in globular clustersgroupings of stars which are the “smallest building blocks of galaxies”.
Many globular clusters merged with the Milky Way galaxy billions of years ago after being pulled into its orbit by the galaxy. gravitational pull. But even today, astronomers can make out their remains among the stars.
“Globular clusters are special because they tear apart [when they fall into the galaxy]but they still live as cohesive clusters of stars in the sky as stellar streams,” Balbinot told Space.com. “So the first thing I’m going to do after I finish downloading this gigantic dataset is to search for these dissolved streams of stars.”
Balbinot is particularly eager to dig into a large set of measurements of radial velocities, the motion of stars away from or toward the observer. Obtaining these measurements is no small feat, as stars tend to be so far apart that the difference Gaia measures over mere years of human time is barely noticeable. However, the telescope, accompanying the Earth in its orbit around the sun in the Lagrange point 2 (the same region where the The James Webb Space Telescope sits), is getting better at the task. It is from these radial velocities that Balbinot and his colleagues hope to reconstruct the finer structure of the Milky Way.
“The sample of radial velocities will be larger by a factor of 10 than previously available,” Balbinot said. “And that’s really exciting. You can find these clusters of stars that move in the same way and basically reconstruct where they came from.”
A living map
Data from Gaia allows astronomers to do more than just map the Milky Way as it is today. Since objects in space follow the rules of physics, the data allows them to model the trajectories of stars millions or even billions of years in the past and future. The result is a three-dimensional movie of the evolution of the galaxy that becomes finer and finer, and stretches farther into the past.
The new data release will inject color into this map as it contains information on the 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 the 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 on chemical compositions with the trajectories of stars reconstructed from Gaia’s measurements, astronomers can track stars back to their birthplace. They can not only identify which part of the Milky Way each group of stars formed in, but also spot those that arrived from elsewhere. (The Milky Way as we see it today was born collisions with other smaller galaxies. Stars from these other galaxies have a unique chemical fingerprint.)
“One of the exciting things you can do with Gaia is you can find these similarly moving groups of stars and basically reconstruct where they came from, and what building block brought them into our Milky Way. “, said Balbinot. “At the end of the day, [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 in fact, that’s only about 1% of the predicted number of stars in the Milky Way galaxy. Using sophisticated algorithms and a wealth of scientific knowledge, astronomers can extrapolate what they learn from Gaia to better understand the galaxy as a whole. One of the open questions they hope to learn more about is the Milky Way characteristic spiral structure.
Most astronomers agree that the Milky Way has four spiral arms, the dense streams of stars and gas that seem to emanate from the center of the galaxy. But there are quite a few points of contention around those spiral arms. Astronomers are still debating the size and prominence of the individual arms, as well as their exact position within the Milky Way’s disk. The new data could help reveal the spiral structure with better clarity.
“With the astrophysical parameters we have now, we can directly create star samples for specific scientific cases,” Jos de Bruijne, Gaia project scientist at the European Space Agency, told Space.com. “We know that the spiral arms are mostly made up of young stars. This is where stars form. So with the new data we can look at, for example, stars that are no more than 100 million in size. ‘years.” (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.)
To see further
Balbinot said the new dataset will reveal information about stars much further from Earth than previous versions of Gaia. Some of these stars are at the very edge of the Milky Way, where the so-called galactic halothe diffuse sphere of finely dispersed stars surrounding the galaxy’s much more massive disk meets intergalactic space.
“These are variable stars, very bright stars that vary in brightness over time,” Balbinot said. “Because of their brightness, we can detect them even very far away. Some of these stars are on the very edge of the Milky Way, and that’s very exciting because it really is uncharted territory. Everything we find there will be new and exciting.”
In these distant regions of the galaxy, Balbinot hopes to find evidence of older galactic collisions and to distinguish the structures that have emerged from them.
“These collisions leave behind various types of debris,” he said. “Sometimes it’s the stellar streams, but sometimes it can create shells, spherical features in the halo of the Milky Way. I think with these variable stars, we might be able to pick up some of these shells in the outer halo. And that would help us reconstruct in detail how these collisions occurred.”