Astronomers have found the biggest stream of stars ever recorded. This tendril of stars is extraordinarily faint, but it and others like it could eventually help us unveil the true nature of dark matter.
The stream of stars, called the Giant Coma Stream, appears to float unmoored from any particular galaxy in the Coma galaxy cluster, about 300 million light years away from Earth. at the University of Groningen in the Netherlands and his colleagues spotted it using the relatively small Jeanne Rich Telescope in California before taking follow-up observations with the much larger William Herschel Telescope in Spain.
They found that the Giant Coma Stream measures nearly 1.7 million light years long and only about 81,000 light years wide, making it the longest such stream ever spotted. It has an estimated mass about 68 million times that of the sun. 鈥淲e have thin streams in our galaxy, but the size of this one is completely huge compared to those,鈥� says Rom谩n.
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The size and structure of the stream suggest that it was once a galaxy in its own right. 鈥淚n the beginning this was just an ordinary dwarf galaxy, but it fell into the cluster and the tidal forces stretched it into this thin structure,鈥� says Rom谩n. 鈥淭hese thin streams are very fragile, and to observe such a fragile structure in a galactic cluster is very striking, because this is a very violent environment in which galaxies interact with each other.鈥�
The very violence that created the stream of stars will probably destroy it within the next few million years, he says. Before then, though, it could prove a useful tool for investigating dark matter.
According to our standard model of cosmology, dark matter should clump up into 鈥渉aloes鈥�. As the galaxies in the Coma cluster whip around one another, so too should these haloes. Eventually some could barrel through the stream, leaving holes behind. These perturbations could be used to investigate the nature of the dark matter in the haloes, says Rom谩n.
We could learn even more about dark matter, as well as the formation and evolution of galaxies, with more examples of streams like the Giant Coma Stream. Even with their extreme faintness, these objects should be visible to the next generation of telescopes, such as the Euclid space telescope that launched in June, so scientists have high hopes we will find more in the coming years.
Astronomy & Astrophysics
