Astronomers have discovered what is thought to be the largest known black hole orbiting a star. This new object has a hot, highly evolved star as an orbiting companion which allowed it's mass to be measured to be between 24 and 33 solar masses. In 2006, Andrea Prestwich of the Harvard-Smithsonian Center for Astrophysics in Massachusetts, and a team of colleagues had observed the dwarf galaxy IC 10, which is located in the constellation Cassiopeia. Upon observations of this galaxy with NASA's Chandra X-ray Observatory, it was noticed that the galaxies brightest X-ray source(IC 10 X-1), showed sharp changes in brightness which suggested a star passing in front of a companion black hole. Using NASA's Swift satellite as well as observations from the Gemini Telescope in Hawaii, Prestwich and her team found that the star in IC 10 X-1, appeared to orbit in a plane that lies edge-on to Earth's line of sight, and using the speed at which the two stars orbited one another, calculations showed that the black hole must have a mass of at least 24 solar masses. These calculations were surprising to many however because it was believed that massive stars in our galaxy leave behind black holes of about 20 solar masses, and it seems that the IC 10 X-1 was born heavier than that.
I think it is exciting that we are continually increasing what appeared to be limits on the size of black holes in our universe. This shows that there is still an extensive amount of knowledge to be gained from space, which is encouraging for young astronomers like myself. The ability to break previous “records” also shows that we are in fact always getting one step closer to understanding the universe. However, I would be interested to read the article written about these observations to learn with what certainty they made observations such as the line of sight. Isn't it possible that if the perceived inclination of this eclipse is off, then the calculations of mass could as well be in accurate? The article only said that the star “appeared” to be edge-on in the Earth's line of sight but discussed nothing further. The other thing that bothered me about this article, although trivial was the concluding quote by Roy Kilgard of Wesleyan University. Kilgard said “Massive stars in our galaxy today are probably not producing very heavy stellar-mass black holes like this one, but there could be millions of heavy stellar-mass black holes lurking out there that were produced early in the Milky Way's history, before it had a chance to build up heavy elements.” Unless Kilgard made this perceived insight before these observations were announced, then anyone's (amateur or professional) response to his statement would be “duh”, because Prestwich and her colleagues just proved that there could be much more massive black holes in galaxies beyond our own.
Article found at: http://www.sciencedaily.com/releases/2007/10/071030112102.htm
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