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A Yellow Supergiant Progenitor of a Massive Star Supernova in M51

The uncertainty of science: Astronomers have determined that the star that went supernova in the Whirlpool Galaxy (M51) in June — making it the nearest supernova in 25 years — was a yellow supergiant star, not an aging red supergiant as predicted by theory. From the preprint paper:

Despite the canonical prediction that Type II supernovae arise from red supergiants, there is mounting evidence that some stars explode as yellow supergiants. A handful of Type II supernovae have been observed to arise from yellow supergiants: supernovae 1993J, 2008cn, and 2009kr. The locations of the progenitors on the Hertzsprung-Russell diagram shows clearly that these stars are not located on the predicted end points for single star stellar evolution tracks. In addition, despite arising from supposedly similar yellow supergiant progenitors, these supernovae display a wide range of properties.

The Hertzsprung-Russell diagram is a graph mapping the color of stars against their luminosity. Because color and brightness change as the star evolves over time, the graph is used by astronomers to track the birth, growth, and death of stars. That these yellow supergiants don’t appear to be at “the predicted end points for single star evolution” on the diagram is a serious problem for the theorists who have tried to explain what causes this particular type of supernova.

Which also means astronomers are still unable to tell us what stars in the sky are most likely to go supernova in the future.

The progenitor of the May supernova in M51 identified

supernova 2011dh before it exploded

The progenitor star that produced the May supernovae in the Whirlpool Galaxy (also known as M51) has been identified, and it isn’t what scientists predicted.

In a preprint paper published today on the Los Alamos astro-ph website, astronomers describe the star that exploded as a yellow supergiant, not a red supergiant or Wolf-Rayet star, as predicted by the theory explaining this particular type of supernova. Moreover, though theory also favors the star being a member of a binary system, the progenitor of 2011dh appears to be a lone star, not even a member of a cluster.
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