A billion-year-old star river crosses the southern skies

Astronomers from the University of Vienna have identified a river of stars crossing our galaxy and covering most of the southern sky. The estimated 4,000 stars that make up the creek are born together and have been moving together for a billion years, making it a rare phenomenon, as most star clusters disperse quickly once formed.

Typically, when star clusters form, they do not contain enough stars to create enough gravity to hold them together. Gravitational forces quickly scatter stars throughout the galaxy. But from close space observation, astronomers determined that there were a few groups with enough mass to stay linked to each other for millions of years. The Vienna team was able to identify such a group relatively close to the Milky Way and map it using the Gaia satellite of the European Space Agency.

"Identifying the nearby disk floods is like looking for the needle in a haystack," said João Alves, one of the newspaper's authors, in a statement. "Astronomers have been watching and studying this new stream for a long time because it covers most of the night sky, but only realize now that it is there and that it is huge and very close to the Sun. Finding objects close to home is very useful, it means that they are neither too weak nor too fuzzy to allow a more detailed exploration, as astronomers dream. "

The team found the river by measuring the 3D motion of stars in space and seeing which nearby stars were moving together. Using Gaia's data, they were able to identify 200 stars in the river, but the data suggests that at least 4,000 stars make up the flow. Due to its age, this cluster has already circled the galaxy four times, giving the gravitational forces time to pull the cluster into its stream-like structure.

As the creek is nearby, it is an excellent potential target for hunting missions to the planet and could help us learn more about how stars move in galaxies.

The results are published in the journal Astronomy & Astrophysics.