Swedish and Japanese scientists, after 10 years of research, have found an explanation for the unusual emission lines observed from one of the brightest supernovae ever known in the history of astronomy, the SN 2006gy supernova.
Superbright supernovae are the brightest explosions in space. Supernova SN 2006gy is one of the most studied events of this kind, but its origin has remained unclear to date. In a new study, astronomers led by Anders Jerkstrand of the Department of Astronomy at Stockholm University, Sweden, have discovered high iron abundances in supernova material from spectral lines never seen before from supernovae or other astrophysical objects. This made it possible to propose a new explanation for the origin of the supernova.
“No one has ever compared the spectral lines of neutral iron with the unidentified emission lines of SN 2006gy, since the iron in the material of supernovae is usually in an ionized state. We carried out such a check and found a complete correspondence of the iron line to one of the lines of the analyzed spectrum,”said Yerkstrand.
“The situation became even more interesting when we realized that these lines correspond to very large amounts of iron - about one third of the mass of the Sun. This allowed us to exclude some of the old scenarios of the origin of this supernova and propose our own version instead”.
According to this new model, the precursor to supernova SN 2006gy was a binary system composed of a white dwarf the same size as Earth and a hydrogen-rich massive star roughly the size of our solar system in a tight orbit around the white dwarf. When the envelope of the hydrogen-rich star began to expand at the end of its life cycle, the white dwarf was trapped inside this envelope and spiraled toward its center - which contained the companion star. Upon reaching the center of the envelope, the unstable white dwarf exploded to form a Type Ia supernova. The radiation from this supernova then collided with the gas of the envelope escaping from the star, and as a result of this powerful collision, the superbright source SN 2006gy was formed, the authors showed.
The research is published in the journal Science.