Scientists Found a Nearby River of Stars

Scientists Found a Nearby River of Stars

Scientists Found a Nearby River of Stars
Image Credits: New Scientist

The Gaia Satellite of the European Space Agency helped the researchers to observe a billion-year-old river of stars.

Many people might have read the novel, ‘River of Stars’ by Guy Gavriel Kay. However, what would be your reaction if we tell you that astronomers have discovered an actual river of stars by using the data from the Gaia Satellite? Yes, that’s true! Also known as a ‘Stellar Stream’, the 4000-star stream is only 326 light-years away and covers most of the southern celestial hemisphere.

Is this a new discovery?

A number of rivers of stars are known to exist in the Milky Way. Despite that, this recent discovery is a completely new experience for researchers. The stars, although looking close in pictures, are actually dispersing into space as the Milky Way’s gravity is pulling them apart. The cluster itself has completed at least four laps around our galaxy and has transformed from a cluster to a stream as it gets affected by the gravitational pull. As of now, the stream is quite close to our planet: a mere 326 light-years.

A funny thing about this discovery is that astronomers have already seen these stars in the past but were not able to identify the entire river of stars. Consequently, it is pretty easy to predict that they were shocked by this finding. Due to the sensitivity limitations of Gaia, only 200 sources were selected. While examining the stars that are moving together in the vicinity of our Sun, the researchers were able to identify 200 stars that fit the pattern of a star cluster being pulled apart by the gravitational force of the galaxy. An extrapolation beyond suggests that this river of stars contains at least 4000 stars, which makes it significantly larger than the previously known clusters.

Why are Researchers Excited about this River of Stars? 

As mentioned before, star streams are not something unknown to humans. It is quite possible to calculate the mass of the entire Milky Way using the data from these rivers of stars. Stefan Meingast, the Lead Author of the paper, elaborated these star clusters in the following words:

“Most star clusters in the galactic disk disperse rapidly after their birth as they do not contain enough stars to create a deep gravitational potential well, or in other words, they do not have enough glue to keep them together. Even in the immediate solar neighborhood, there are, however, a few clusters with sufficient stellar mass to remain bound for several hundred million years. So, in principle, similar, large, stream-like remnants of clusters or associations should also be part of the Milky Way disk.”

The Second Author of the research, João Alves, talked about how difficult it is to identify these disk streams, although they cover most parts of the sky. He mentioned that identifying nearby disk streams is like looking for the proverbial needle in a haystack. Astronomers have been looking at, and through, this new stream for a long time, as it covers most of the night sky, but only now realize it is there, and it is huge and shockingly close to the Sun. Finding things close to home is very useful, it means they are not too faint nor too blurred for further detailed exploration, as astronomers dream.

3D Motion of the Stream

The actual stream of stars was visually separated once its 3D motion was studied. It was only then that the researchers were able to point out similar characteristics between the distributions of stars moving and previously discovered proverbial rivers. Verena Fürnkranz, a Co-author of the study who is also a Masters student at the University of Vienna, referred to that by saying,

“As soon as we investigated this particular group of stars in more detail, we knew that we had found what we were looking for: A coeval, stream-like structure, stretching for hundreds of parsecs across a third of the entire sky. It was so thrilling to be part of a new discovery.”

The discovered stream of stars is so huge that it stretches across at least a third of the night sky. It is at a staggering 1300 light-years long and about 160 light-years wide. It is believed the river of stars may contain more stars than what the initial data from Gaia showed. Researchers say that the river can be used as a valuable asset to help calculate the mass of our galaxy. It is possible that in the near future, astronomers will be able to test the gravitational field of the Milky Way and learn more about how galaxies get their stars. The stream could also be taken as a target for planet-hunting as it is quite close to our planet. 

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