A Star at Death's Door

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Science  02 Jan 2009:
Vol. 323, Issue 5910, pp. 16
DOI: 10.1126/science.323.5910.16b

Some stars die violent deaths. If they are born with masses above about eight times that of the Sun, they become unstable as they approach the end of their nuclear fusion lives and collapse under the force of gravity. As a result they explode as supernovae, producing a sudden radiation burst that can outshine an entire galaxy for a short period of time. Such events don't usually go unnoticed; astronomers have been observing them over the centuries. However, very few stars have been observed right before their death, given the need to presciently acquire high-resolution images of the galaxy in question at just the right time.

Mattila et al. used the European Southern Observatory Science Archive to find high-quality images of the pre-explosion site of supernova 2008bk, which was discovered in March 2008 in a galaxy 13 million light-years from Earth. By comparing the archive observations with a new image of the supernova they took using the adaptive optics system on the Very Large Telescope, they were able to unambiguously identify the star that exploded—an unfortunate red supergiant that started its life with a mass 8.5 times that of the Sun. The observation is consistent with theoretical models of supernovae, and provides further constraints on their progenitors. — MJC

Astrophys. J. 688, L91 (2008).

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