Tau.Neutrino said:
Birth of a black hole witnessed as star vanishes without a bang
For the first time, astronomers have witnessed a star disappear right before their eyes. Known as N6946-BH1, the star appears to have collapsed into a black hole without the usual flair of a supernova, which not only marks the first time scientists have witnessed the birth of a black hole, but could change our understanding of the life and death of stars.
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> According to conventional thinking, when a star exhausts its energy supply, it violently ejects most of its matter outwards in a supernova, before collapsing in on itself to form a black hole.
Yes. But it’s also well known that the explosion can be created in several different ways. At different stages of collapse depending on the star’s initial mass distribution.
> Some 22 million light-years from Earth, the star N6946-BH1 is located in the galaxy NGC 6946, which is often known as the Fireworks Galaxy due to how regularly its stars go supernova. But this one was different. Telescope images show that N6946-BH1 was clearly visible in 2007, brightened slightly around 2009, and had vanished completely by 2015.
Well, computer models of the collapse of massive stars have yet to explain how a supernova happens. So it should be a relief to astrophysicists that sometimes it doesn’t.
> “N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey,” says Scott Adams, co-author of the study. “During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring.
We already have “supernova imposters”, stars that appear to blow up like a supernova but after the “supernova” has finished the original star is still there. Eta Carinae is the best known. “Examples of supernova impostors include the 1843 eruption of Eta Carinae, P Cygni, SN 1961V, SN 1954J, SN 1997bs, SN 2008S in NGC 6946, and SN 2010dn where detections of the surviving progenitor stars are claimed. One supernova impostor that made news after the fact was the one observed on October 20, 2004, in the galaxy UGC 4904 by Japanese amateur astronomer Koichi Itagaki. This LBV star exploded just two years later, on October 11, 2006, as supernova SN 2006jc.”
According to the attached video, the star is still visible in IR, which means that the possibility that it’s just obscured by dust isn’t completely ruled out yet, but that will be tested more rigorously later.
By the way, the images of this galaxy in 2007 and 2015 are the best I’ve seen of how Hubble’s WFC3 is heaps better then the old camera WFPC2. Look at the improvement in resolution of the Hubble Telescope. The old WFPC2 is on the left and the new WFC3 is on the right.
