Star Formation in the Center of the Milky Way Started at the Core and Then Worked its way out

Star formation and its role in the evolution of the universe are some of the biggest questions facing astronomy. Astronomers are wondering if the process started in the central regions of the universe. It has been shown that the stars formed in the centers of many galaxies after the Bigbang. Astronomers have wanted to study the formation of stars more closely in the past.

Astronomers have found it difficult to discern individual stars and clusters in the center of the Milky Way because of how bright it is. The first reconstruction of the star formation history in the Galactic Center has been created thanks to a new analysis. Most young stars in this region formed in loose stellar associations that dispersed to fill the Galactic Disk over time.

The research was led by Dr. Francisco Nogueras-Lara. He was joined by two other people, the leader of the Lise Meitner Group and the leader of the Galactic Centre Group. The paper that describes their findings was published in the journal Nature Astronomy.

Astronomers use our galaxy to learn about the properties of the rest of the universe, but there are differences between the two. Our galaxy has a relatively low rate of stellar formation, whereasburst galaxies have episodes that last a few million years where they produce tens or even hundreds of solar mass per year. Ten billion years ago, the high formation rate was the norm among the galaxies.

Over the past 100 million years, star formation rates around the SMBH have been ten times higher than average. The core of our galaxy is just as productive as the rest of the universe. Astronomers want to learn more about the factors that influence the formation of stars. Because our Solar System is embedded in the Milky Way's disk, it has been more difficult to study it.

There is a huge amount of light-obscuring dust between Earth and the center of the universe. Astronomers rely on instruments that observe the Universe in various wavelength areas. These can show the radiation absorbed by the dust and reveal objects that are otherwise hidden. The crowded Galactic Center makes it hard to see individual stars, except for the very bright ones that stand out.

ionized radiation and x-ray emissions show that stars are forming in the center of the universe. Young stars that formed in the past million years have been hard to find. About 10% of the expected stellar mass is accounted for by two massive star clusters and a few isolated young stars at the center of our galaxy. There are a lot of unanswered questions about the locations of the other young stars.

The data from the GALACTICNUCLEUS campaign was used by Nogueras-Lara, Neumayer, and Schdel to answer the question. They took pictures of the central region of the Milky Way in the J, H, and K bands and looked at an area of 64,000 square light-years. The combined pictures were used to correct for atmospheric distortion and map the region in much better detail than before.

The GALACTICNUCLEUS survey gave individual data for 3 million stars, compared to a few tens of stars. The team noticed that the area known as Sagittarius B1 has more young stars than other regions because of the way they ionize surrounding gas clouds. Nogueras-Lara and his colleagues were able to study the stars in detail with these high-resolution observations.

For stars that formed around the same time, the distribution of the luminosity is predictable. It's possible to reconstruct a history of star formation based on those that formed between 2 and 7 billion years ago and within the last 2 billion years. The team found that Sag B1 had an older and younger population of stars. Nogueras-Lara was quoted in an MPIA press release.

“Our study represents a big step forward in finding the young stars in the Galactic Center. The young stars we found have a total mass of more than 400,000 solar masses. That is nearly ten times higher than the combined mass of the two massive star clusters that were previously known in the central region.”

The stars were found to be dispersed and not part of a massive cluster, which suggests they were born in one or more looser stellar associations that quickly dissolved as they circled the center over millions of years. The results pertain to Sag B1, so it's possible that young stars in the Galactic Center were born in loose associations. The young populations are more difficult to resolve and need high-resolution surveys.

There is an older population of stars in Sag B 1. There are almost no stars in the intermediate range in the innermost regions of the Galactic Center. It's possible that star formation began in the innermost part of the center and then spread to the small disk of stars surrounding it. This inside-out mechanism of star formation has already been seen in other galaxies, and these latest results suggest this is also true in the Milky Way.

The team hopes to conduct follow-up observations using the K-band Multi-Object Spectrograph. They hope to identify some of the very young stars in the center of the universe by using the observations they made. There are plans to track the motions of the newly-discovered stars using data from missions. The motion of stars in the same association is likely to be the same as time goes on.

Astronomers will be able to deduce if the young stars observed there were born in one or more loose associations by tracking the proper motion of the stars. Nadine Neumayer summed it up.

“Both kinds of measurements will serve to hopefully confirm, but definitely refine, the results of the now-published work. At the same time, we and our colleagues will start exploring what the new insights into star formation in the Galactic Center can tell us about high-productivity star formation in other galaxies.”

There is further reading on MPIA.