Telescope images
have confirmed something astronomers have long suspected, that red supergiant
stars are the stars that explode in so-called type II supernovas.
Type II
supernovas are the impressive cosmic
explosions that result from the internal collapse of a massive star. (For
this reason, they are also known as core-collapse supernovas.)
On average,
a supernova
will occur about once every 50 years in a galaxy the size of the Milky Way. But
scientists don't know when these stellar powder kegs will blow, so identifying
the star that birthed them, called the progenitor star, can be tricky.
Models and
observations had suggested that red supergiants were the progenitors of type II
supernovas, but the best evidence so far has only been able to show that these
stars were in the area before the supernova, not that that they were in the
exact spot.
So astronomer
Justyn Maund of the University of Copenhagen in Denmark and the University of
California, Santa Cruz, and his colleagues used telescope images to answer the
question, "How sure are we that this is the progenitor?" he said.
They used
images from the Hubble Space Telescope and Gemini Telescope from before
and after two supernova explosions, SN 2003gd and SN 1993J. They found that
there were indeed red supergiants in the exact spots where the blasts occurred beforehand,
and that after, "the progenitor is missing," Maund said.
The finding,
detailed in the March 20 issue of the journal Science, confirms the
long-standing theory behind type II supernova formation. "There's no other
way you could get around it in this case," Maund told SPACE.com.
It takes
awhile for scientists to get such confirmations because they have to wait for
the glare of supernovas to die down before they can get a proper "after
image," which can take many years.
Maund and
his team were able to estimate that the progenitor stars had masses that were
about seven times the mass of our sun. They were also able to show that SN
1993J's companion, which sucked away much of its partner's outer hydrogen
envelope, was still hanging around.
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