Friday, August 26, 2011

Star eaten by a black hole: still blasting away | Bad Astronomy | Discover Magazine

Science, especially astronomy, can be very beautiful...

Star eaten by a black hole: still blasting away | Bad Astronomy | Discover Magazine:  "In late March of 2010, an extraordinary event occurred: a black hole in a distant galaxy tore apart and ate a whole star (I wrote about this twice at the time; here’s the original post, and a followup article including a Hubble image of the event).

"Now, there’s more info: the black hole, lying at the center of a galaxy nearly 4 billion light years away, has about 8 million times the mass of the Sun. When it tore the star apart, about half the mass of the star swirled around the black hole, forming twin beams of matter and energy that blasted outward at a large fraction of the speed of light. The folks at NASA’s Goddard Space Flight Center made a great animation
to show this:The star was ripped apart by tides. The thing about black holes is, they’re small: this one was probably about 15 million kilometers across. A typical star is about a million km across (the Sun is 1.4 million kilometers in diameter, for comparison). This means the star could get really close to the black hole, and that’s why it was doomed. The force of gravity drops with distance, so as the star approached, the side of it facing the black hole felt a far greater force than the size facing away. That stretched the star, and the stretching increased as the star got closer. At some point, the force was so great it exceeded the star’s own gravity, and it could no longer hold on to its material. The black hole won — as they usually do."

Credits: Video: NASA; Artist’s illustration of star and black hole: NASA/CXC/M.Weiss.
Followup on the star torn apart by a black hole: Hubble picture | Bad Astronomy | Discover Magazine"I recently wrote about a mind-boggling event: astronomers capturing what are apparently the final moments in a star’s life as it was literally torn apart by a black hole.
"Today, NASA has released some new pictures of the event, including this Hubble Space Telescope shot:"

Image credits: Hubble: NASA/ESA/A. Fruchter (STScI); Swift: NASA/Swift/Stefan Immler; Jet illustration: Don Dixon/NASA/JPL-Caltech.
Astronomers may have witnessed a star torn apart by a black hole | Bad Astronomy | Discover Magazine"On March 28, 2011, NASA’s Swift satellite caught a flash of high-energy X-rays pouring in from deep space. Swift is designed to do this, and since its launch in 2004 has seen hundreds of such things, usually caused by stars exploding at the ends of their lives.

"But this time was hardly "usual". It didn't see a star exploding as a supernova, it saw a star literally getting torn apart as it fell too close to a black hole!"

Swift X-ray image of GRB 110328A — a 41 hour exposure!  Image credits:
Artist’s illustration of star and black hole: NASA/CXC/M.Weiss. Illustration of accretion disk: A. Hobart, CXC. Images from SARA telescopes used by permission of Bill Keel; Swift image: UK Swift Science Data Centre

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