Astrophysicists have discovered a gigantic star stream stretching 1.7 million light years through space. This phenomenon was called the Koma River. Experts believe there may be a hole in the stream through which a chunk of dark matter has penetrated. Astronomers have discovered the largest star shower ever recorded. Although this “stellar stream” is unusually weak, this phenomenon, and others like it, have the potential to help uncover the true nature of dark matter.
This stream of stars, called the Giant Coma Stream, appears to be unrelated to any particular galaxy in the Coma cluster, located about 300 million light-years from Earth in the constellation Coma Coma. Javier Roman, an astrophysicist at the University of Groningen in the Netherlands, and his colleagues discovered the object using the relatively small Jeanne Ricci Telescope in California. The scientists then continued their observations at the much larger William Herschel Telescope Observatory in Spain. “Similar phenomena have been observed in our galaxy, but this river is simply huge compared to them,” Roman said.
The size and structure of the stream indicate that it was once a full-fledged galaxy. “It started out as a regular dwarf galaxy, but then it fell into a star cluster and was stretched by tidal forces into this thin structure,” Roman said. “These subtle currents are highly unstable, and it is very unusual to see such fragile structures within a galaxy cluster. This is a highly turbulent environment where galaxies are constantly interacting. It’s the environment.”
Experts say the same forces that created this star stream will likely destroy it within the next million years. But until then, the phenomenon could prove a useful tool for studying dark matter. According to standard cosmological models, dark matter clumps together under the influence of gravity to form halos. As the galaxies in the Coma Cluster orbit each other, the halo grows larger. At some point, some of them may break through the river and leave a “hole”. According to Roman, such disturbances can be used to study the nature of dark matter.
If we can find more examples of flows like the giant coma flow, we can learn more about dark matter and the formation and evolution of galaxies. Although very faint, such objects should be clearly visible to next-generation telescopes, such as the Euclid Space Observatory launched in June of this year. Scientists really hope to find more such objects in the coming years.