A stunning river of stars has been spotted flowing through intergalactic space in a cluster of galaxies about 300 million light-years away.
These bridges are known as stellar streams; At 1.7 million light-years long, the newly named giant Coma Stream is the longest we have ever seen. And that’s not all: the faint river is the first of its kind to be seen outside the galaxy.
The discovery is a big surprise. In such a dynamic and gravitationally complex environment as a galaxy cluster, something as weak as a stellar stream would not be expected to persist for long at all.
And yet here we are. This discovery could be used to study galaxy clusters in more detail and the mysterious dark matter contained within them.
“This giant stream crossed our path by accident.” says observational astrophysicist Javier Roman University of Groningen in the Netherlands and University of La Laguna in Spain.
“We were studying star halos around large galaxies.”
Stellar streams are fairly common in the Milky Way. They are believed to be the fragmented remains of dense spherical star clusters, broken up by tidal forces in the Milky Way. But they are difficult to recognize; The association of stars is not immediately obvious, because it is very difficult to measure distances to stars, and the tables are very faint.
In intergalactic space, this weakness also makes it difficult to detect loose connections of objects. Space is full of very bright objects; The duller something is, the more likely it is to be lost.
But in recent years, telescope technology and analytical techniques have revealed much fainter objects than we were able to identify in the past; Such is the case with the giant coma stream.
Roman and his colleagues were using the 0.7-meter Jean Rich Telescope and the 4.2-meter William Herschel Telescope to search for faint structures within the galaxy. Coma groupIt is a group containing thousands of known galaxies.
They were trying to study galactic halos – diffuse spherical regions of scattered stars and dark matter that comprise the inhabited planes of galaxies.
However, their data revealed the unexpected: a long, extended ribbon of stars, located not within a galaxy, but between cluster galaxies.
This ribbon is distinctly different from the fragile threads of the cosmic web that bind galaxies together within clusters as well. It resembled nothing so much as the stellar streams within the Milky Way, but on a much more mythical scale.
Although they are very large and appear peaceful, galaxy clusters are chaotic environments due to gravity, with the massive objects within them pushing and pulling each other in every direction.
The researchers found that a stellar stream would not be expected to survive for long in such an environment, but this environment gives us some clues about the origins of the stream.
They ran simulations and found that such jets, although rare, can form in a galaxy cluster — from a dwarf galaxy breaking apart due to the gravity of larger galaxies.
Cosmically speaking, it is not expected to last long; Fortunately, at this time in the universe’s history, we have the technology to see structure continuing to disintegrate.
But their presence can be used to study that cluster environment. Since galaxy clusters are full of mysterious dark matter, this arouses the interest of scientists who are trying to find out what this matter consists of.
The giant coma current also suggests that similar structures may be found in other groups. Researchers hope to use larger telescopes to look more closely at these huge clusters, to find other secrets that we may have missed.
They hope to get a closer look at the giant coma current itself.
“We would like to observe individual stars in and near the stream and learn more about dark matter.” says astronomer Reinier Pelletier From the University of Groningen.
The research was published in Astronomy and astrophysics.
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