Omega Centauri globular cluster

[ilan]

Astronomers Find Stars Streaming from Our Galaxy’s Biggest Cluster
Monica Young, Sky & Telescope| April 22, 2019

Astronomers have discovered a stream of stars pulled from Omega Centauri, the largest and most brilliant globular cluster around the Milky Way — and perhaps a one-time dwarf galaxy.

A view of the iconic Omega Centauri globular cluster.
ESO / INAF-VST / OmegaCAM; Acknowledgement: A. Grado, L. Limatola / INAF-Capodimonte Observatory​

Omega Centauri (NGC 5139, or Omega Cen for short) is unusually brilliant, massive, and huge: 10 million stars squeeze into a sphere about 150 light-years wide. What most puzzles astronomers, though, is that its stars come in at least three distinct populations, suggesting the cluster came together over billions of years instead of all at once.

Astronomers have long thought this peculiar globular might be something else altogether: the remains of a galaxy that came too close to the Milky Way. Torn apart by our galaxy’s gravity, its stars would have streamed into the halo and looped around the galaxy, leaving a small cluster-like core behind.

Now, Rodrigo Ibata (University of Strasbourg, France) and colleagues report new evidence for this theory in Nature Astronomy: the long-sought detection of a stellar stream belonging to Omega Cen.

Researchers have been looking for (and finding) the stellar remains of torn-apart clusters and galaxies ever since the first streams were discovered in the Sloan Digital Sky Survey, but it’s been rough going. “Streams have been hard to detect because they are so low in density and therefore hard to detect visually,” explains Jeremy Webb (University of Toronto), who was not involved in the study. “Most do not stand out visually amongst foreground and background stars.”
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Star clusters are amazing looking stellar phenomena. Now we think some could be the remnants of a celestial "disaster." - ilan