laklak wrote:Interglactic gas. I knew it, the universe is a cosmic fart.

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.

Around the Milky Way are more than 150 globular clusters, ancient star cities with hundreds of thousands of closely packed denizens. Most such clusters can be found out in the galaxy’s nearly empty halo; it’s likely they formed before our galaxy did. But one of these is not like the others.

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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.

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Alan B wrote:Are there other large masses (galaxies) in the right position to cause this 'twisting' by gravitational forces?

A team at the University of Warsaw measured the positions and distances of supergiant stars known as Cepheids, using the Optical Gravitational Lensing Experiment telescope at Las Campanas Observatory in Chile — a project that has doubled the number of known Cepheids in the Milky Way. Mapping the distances traces the Milky Way’s spiral arms, and how the disk warps at its farthest reaches, to form an S-shape when seen side-on.

The data haul includes the positions of nearly 1.7 billion stars, and the distances, colours, velocities and directions of motion of about 1.3 billion of them. Together, they form an unprecedented live movie of the sky, covering a volume of space 1,000 times larger than that captured by any previous survey (see ‘Gaia’s gold’). “In my professional opinion, this is crazy awesome,” says Megan Bedell of the Center for Computational Astrophysics in New York City, one of the many astronomers who will conduct studies based on the data set. “I think the whole community is eager to dive in.”

newolder wrote:Indeed, the flaring increases the thickness near the warp edges by a factor of 3 compared to the 700 light year thickness hereabouts.