March 23, 2009 | David F. Coppedge

Whoops, the Wrong Star Exploded

“Our understanding of the evolution of massive stars before their final explosions as supernovae is incomplete, from both an observational and a theoretical standpoint.”  That’s how a paper in Nature begins.1  Avishay Gal-Yam was not kidding; a star exploded that theory says was not supposed to.
    The famous supernova 1987A was already an anomaly.  Its progenitor was a blue supergiant.  That fact “required a rethink of stellar evolution models,” they said.  Now, the progenitor of a supernova in 2005 has been identified. 

The progenitor of supernova SN 2005gl was proposed to be an extremely luminous object, but the association was not robustly established (it was not even clear that the putative progenitor was a single luminous star).  Here we report that the previously proposed object was indeed the progenitor star of SN 2005gl.  This very massive star was likely a luminous blue variable that standard stellar evolution predicts should not have exploded in that state.

Massive stars are not supposed to explode during the Luminous Blue Variable (LBV) stage, but this one did.  The astronomers think, based on the unexpectedly low amount of material flung off from the star, that the material collapsed into a black hole 10-15 times the mass of our sun.
    How serious is this disconnect between theory and observation?  Gal-Yam told, “This might mean that we are fundamentally wrong about the evolution of massive stars, and that theories need revising.”  It shows also that “The unexpected explosion could mean other stars may behave in ways not previously expected,” the article said.  Astronomers are scrambling to figure out what happened.
    So the tidy models of core collapse of red giants may not be the whole story.  “This also leaves open the question that there may be other mechanisms for triggering supernova explosions,” Gal-Yam said.  “We may be missing something very basic in understanding how a superluminous star goes through mass loss.” 

1.  A. Gal-Yam and D. C. Leonard, “A massive hypergiant star as the progenitor of the supernova SN 2005gl,” Nature doi:10.1038/nature07934, published online March 22, 2009.

Fundamental misunderstanding, missing something very basic, requiring a rethink…. and this is in one of the hard sciences, not the squishy stuff of which Darwinism is made.  Lesson learned?

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Categories: Physics

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