An Unusual Supernova May Be a Missing Link in Stellar Evolution Research
(PhysOrg.com) -- After the discovery of an unusual Type Ib Supernova (SN) 2005cz in an elliptical galaxy, an international team of astronomers used the Subaru Telescope to monitor it. Their findings provide the first solid evidence of the theoretical prediction that stars in the 8-12 solar mass range can explode into supernovae.
A research group led by Koji Kawabata of Hiroshima University, Keiichi Maeda, Ken’ichi Nomoto, Masaomi Tanaka of IPMU and their collaborators published their result in Nature (2010 May 20 issue).
In the paper, they reported observations of a peculiar type Ib supernova 2005cz, and concluded that this is a supernova whose progenitor mass at its birth was about 10 times the Sun. Such a star represents a boundary between stars that end their lives with the gigantic supernova explosion and those without explosions.
Supernovae from stars that were originally about 10 solar mass should occupy a large fraction of supernova explosions taking place in the whole universe. However a supernova whose progenitor mass lies just above the boundary has not been identified. This is a reason why astronomers have been seeking for an explosion in this mass range. This study thus finally provides a solid confirmation on the stellar evolution theory.
Having identified properties of the resulting supernova explosion, this study also serves as an important step forward to understand roles of supernovae in evolution of the universe.
The team proposed that these peculiarities are well explained by rather 'normal' core-collapse supernova from a less massive progenitor star (main-sequence mass of approximately 10 solar mass) than other Type Ib SNe. This mass corresponds to the low-mass end of the range of massive stars that explode. Such stars die as supernova about a few ten milion years after their birth, which is consistent with the recent studies suggesting that the host galaxy probably underwent a galactic merger and would stimulate a global star formation 10-100 milion years ago. This is the first evidence of the theoretical prediction that stars in the 8-12 solar mass range can explode as supernovae. Such stars might have a very special abundance pattern in the ejecta and play important roles in the chemical evolution of galaxies.
Provided by Subaru Telescope
