Giant stars may not be necessary for supernovae

New research using X-ray and ultraviolet data helps scientists to better understand the origins of supernovae. These exploding stars are important in measuring distance in the universe.

All that remains of the oldest documented example of a supernova, called RCW 86, is seen in this image, a combination of data from four different space telescopes to create a multi-wavelength view, released by NASA in 2011. Scientists are beginning to understand the origins of one type of supernova.

Though supernovae are valuable to scientists in their attempts to understand the universe, the environment that creates them is not well known.

"For all their importance, it's a bit embarrassing for astronomers that we don't know fundamental facts about the environs of these supernovae," said Stefan Immler, an astrophysicist at NASA's Goddard Space Flight Center in a press release.

Now NASA scientists, with the help of the Swift satellite, are beginning to zero in on the origins of an exploding star called Type Ia supernovae.

We currently know that supernovae occur when gas flows into a white dwarf, a small, dense star similar in mass to the Sun and in volume to the Earth. The gas flowing in adds mass to the dwarf until it reaches a critical threshold and explodes.

Supernovae release large, consistent, visible energy for several weeks, allowing scientists to measure the exploding star's distance from Earth.

But what type of stars are necessary ingredients for a supernova?

To answer this question, scientists have analyzed information from the Swift satellite. New X-ray and ultraviolet data provides scientists with a clearer picture of the events leading up to these stars' explosions.

In two separate studies, they found that it is unlikely that supergiant stars are present during a supernova. This suggests that the energy feeding the white dwarf is likely coming from another white dwarf or some other small, young star, similar to the Sun.

Other recent studies appear to support these findings. Preliminary results of unpublished research led by Alicia Soderberg at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., suggest that SN 2011fe, the closest Type Ia supernova since 1986, was caused by merging white dwarfs.

The X-ray study will be published in the April 1 issue of The Astrophysical Journal Letters and The Astrophysical Journal will publish the ultraviolet discovery on April 10.

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