A treasure trove of data is set to answer some big questions.

The data compiled by the European Space Agency contains more than one billion objects in the sky. Astronomers hope the new data will help solve some major mysteries about the birth and life of the stars.

The most detailed map of the Milky Way was created by the Gaia mission, which charts the precise positions, distances and velocities of nearly 2 billion stars. The upcoming data set will reveal the chemical composition of tens of millions of stars, which will allow astronomer to answer important questions.

Every two months, Gaia scans the entire sky around the Lagrange Point 2, not too far from the James Webb Space Telescope. Only 1% of the stars in the Milky Way are seen by the telescope. Astronomers can use the data from those measurements to learn more about the whole of the galaxy.

Some of the most fascinating mysteries the Milky Way explorers are eager to crack are listed here.

How many stars are in the sky?

1. Where do stars come from? 

By measuring the precise positions, distances and velocities of vast quantities of stars, Gaia does much more than map the Milky Way as it is today. Because objects in the universe follow the rules of physics, astronomer can model the past trajectory of stars and play the movie of the Milky Way back and forth millions of years. That was already possible with the data that was released. Astronomers will be able to look for more with the new data set.

For the first time, the Gaia mission team will release astrophysical parameters for half a billion stars. The parameters derive from the light spectrum of the stars measured by Gaia, which reveal information about the chemical composition, mass, age, temperature and brightness of each of the stars. The scientist told Space.com that it was a big deal.

The Milky Way has four spiral arms.

The Milky Way has four spiral arms, but astronomers still debate about their sizes and positions. (Image credit: NASA/JPL-Caltech)

De Bruijne said that you will get to know the stars. It is like having an anonymous group of 500 million people and now you get to know every single one of them.

According to De Bruijne, the chemical composition of stellar atmospheres is the same as the chemical composition of the molecular clouds that these stars were born in. Astronomers will be able to track groups of stars to their birthplaces inside and outside the Milky Way by combining the information about chemical composition with the modeling of stellar trajectory.

It is difficult and expensive to do this with ground-based telescopes, but we can now do it with a high number of stars.

2. How does the galaxy "hang" together? 

Astronomers don't know a lot about the galaxy despite the fact that Gaia has been looking at it. It is not easy to study our home. Because we are inside the galaxy, we cannot see the forest for the trees.

The big picture is coming together, piece by piece, thanks to the gradual improvements in Gaia data and other observation techniques. We are getting closer to figuring out the distribution of dark matter in the universe.

All the stuff in the galaxy exerts gravity at every star, and this gravity determines how fast the star moves, according to De Bruijne. It's important for figuring out how the galaxy hangs together.

There are still uncertainties about the distribution of stars in the Milky Way. The dense streams of stars and gas that appear to come from the center of the galaxy are mostly agreed upon by Astronomers. Astronomers still debate the size and prominence of the individual arms, as well as their exact position in the Milky Way's disk. The spiral structure might be revealed with better clarity thanks to the new data.

De Bruijne said that they can create samples of stars for specific science cases. It is where stars form. We can look at stars that are no older than 100 million years with the new data. Our sun is 4.5 billion years old and will die in 5 billion years.

Astronomers can model the evolution of the spiral arms into the past and the future with the help of the spiral arms being seen as they are today.

Anthony Brown, an astronomer at Leiden University in the Netherlands and chair of the Gaia Data Processing and Analysis Consortium, told Space that with the new data, they will be able to look farther away from the sun. Understanding the whole of the galaxy will be a challenge.

3. What happened in the Milky Way's "childhood"? 

Dwarf galaxies orbiting the Milky Way galaxy.

The Milky Way has grown over billions of years by devouring smaller galaxies that fall into its orbit. (Image credit: ESA/Gaia/DPAC)

By reconstructing the trajectory of millions of stars, they can learn about events that happened in the distant past. The ripples of which can be seen in the galaxy to this day are the result of these events.

One of the most famous discoveries that came out of the earlier data releases was the collision of a smaller galaxy called Gaia Enceladus, which happened 8 billion to 11 billion years ago. The Milky Way was much smaller back then, and when it devoured the smaller person, it had a lot of upheaval. The last significant merger that the Milky Way underwent in its violent childhood was the collision with Gaia Enceladus. He hopes that with the new data set, they will be able to look further back into the history of the universe.

Some authors are trying to look more than 10 billion years into the past at the first signs of the Milky Way. Now that we know the ages and the chemical compositions of stars, we can figure out the time order in which events happened, and we can also see where stars originally came from.

Smaller galaxies are being eaten by the Milky Way. One day, the Large Magellanic Cloud and the Small Magellanic Cloud will be swallowed up by the Milky Way, according to models. Brown said that the remnants of other dwarf galaxies can be seen in the form of stellar streams.

The Milky Way will die a violent death one day. The Andromeda galaxy will be 4.5 billion years from now. Humans are unlikely to see the collision at the same time as the sun dies. Brown said that the new data release may shed some light on the event.

4. What's wrong with the Milky Way's disk? 

The structure of the Milky Way with its rotating warped galactic disk.

The structure of the Milky Way with its rotating warped galactic disk. (Image credit: Stefan Payne-Wardenaar; Inset: NASA/JPL-Caltech; Layout: ESA)

The disk of the Milky Way is warped, rather than flat, according to data from Gaia. Astronomers think the wobble was caused by a crash.

Brown hopes that the new data will shed light on the origins of the disturbance. The upcoming data release will contain information about the motion of more than 30 million stars in the line of sight, that is, how fast they move toward or away from the telescope. The previous releases only had radial velocities of 7 million stars. The more information the astronomer has, the better their analysis tools are.

Brown said that they can try to measure the disturbance in different locations in the galaxy or look at how it affects certain types of stars. This is the kind of thing that you can do with the expanded data sample.

And more is yet to come

According to De Bruijne, the best is yet to come, as the scientific mission of Gaia is currently generating the most scientific papers. The June 13 data dump will contain the largest-ever set of information about the stars in the Milky Way, and De Bruijne expects that data to lead to new discoveries.

The largest database of chemical compositions of asteroids has been assembled by Gaia. Scientists will be able to learn more about the stars they see thanks to the improved algorithms being developed by the consortium. When the mission runs out of fuel, it will stop scanning the sky. Thousands of newly discovered exoplanets are expected to be revealed in two more big data releases, which are expected to follow the one on June 13, according to De Bruijne.

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