Astronomers don’t win because of fears. Around this time, an international team of researchers was surprised to see an enormous ‘stream of stars’ flowing like a river between more than 1,000 galaxies in the well-known Coma cluster, 300 million light-years from Earth.
Stellar streams were already known within our Milky Way and other nearby galaxies, but one flows in the middle of the vacuum of space, between one galaxy and another. At 1.7 million light-years long, the galactic river, known as the ‘Giant Coma Stream’, is the longest ever seen by astronomers. An incredible discovery has just been published’Astronomy & Astrophysics‘.
Got it by accident
The first observations were made with the relatively small 70 cm telescope of astronomer and paper co-author Michael Rich in California. But by focusing on the region with the 4.2-metre William Herschel telescope, taking new images and processing them, astronomers were able to clearly see the stream of stars, a ‘river of light’ ten times the length of our planet. The Milky Way floats in space, among the galaxies, but not associated with anything in particular.
“This massive star stream – says the paper’s lead author Javier Roman, from the Universities of Groningen and La Laguna in Tenerife, the Netherlands – crossed our path by chance. “When we saw it, we were studying the halos of stars around large galaxies.”
The discovery is surprising because the giant coma stream is a fragile system in the middle of a hostile environment of galaxies that constantly attract and repel each other. According to another of the study’s authors, Rainer Pelletier, after the unexpected discovery “we were able to simulate such massive flows on the computer. So we hope to find more of them. For example, we can use the future 39-meter ELT (Very Large Telescope) and the Euclid mission recently launched by the European Space Agency to generate data. We’ll see when it starts.”
With these telescopes, Peletier continues, researchers are not only looking for new giant streams of stars, but also approaching the Coma giant stream and trying to figure out how such structure can survive in a gravitationally chaotic environment. Researchers, in fact, do not expect the flow of stars to be maintained for a very long time (a few million years), although each of its last secrets can be extracted.