A Nearby Supernova

m82_supernovaThis past January, astronomers witnessed a supernova soon after it exploded in the galaxy known as Messier 82 or M82. Telescopes around the world and in orbit turned their attention to study this newly exploded star, including the Chandra X-ray Observatory. It seems that this supernova, cataloged as SN 2014J, belongs to a class of explosions called “Type Ia” supernovas. The predominant theory is that all Type Ia supernovas involve the detonation of a white dwarf, but there is a question as to whether the fuse on the explosion is lit when the white dwarf pulls too much material from a companion star like the Sun or when two white dwarf stars merge.

This image contains data from Chandra with low, medium, and high-energy X-rays shown in red, green, and blue respectively. The boxes in the bottom of the image show close-up views of the region around the supernova in data taken prior to the explosion (left), as well as data gathered in February after the supernova exploded (right). The lack of the detection of X-rays detected by Chandra is an important clue for astronomers looking for the exact mechanism causing the supernova.

The lack of X-rays suggests that the region around the site of the supernova explosion is relatively devoid of matter. That’s a critical clue to the origin of the explosion. If the white dwarf exploded because it had been steadily collecting matter from a companion star prior to going nova, the mass transfer process would not be 100% efficient, and the white dwarf would be immersed in a cloud of gas. If a significant amount of material were surrounding the doomed star, the blast wave generated by the supernova would have struck it by the time of the Chandra observation, producing a bright X-ray source. The lack of x-rays shows that the region around SN 2014J is exceptionally clean.

One possible explanation is that the explosion was caused by the merger of two white dwarf stars. In that case there might have been little mass transfer and pollution of the environment before the explosion. Another possible explanation is that several smaller eruptions on the surface of the white dwarf cleared the region prior to the supernova. Further observations made over the next months could show on the amount of gas in a larger volume and help decide between these and other scenarios.

Image Credit: NASA