Yellow Supergiant Star
April 6, 2013

New Evidence Of Supernova Progenitor

John P. Millis, Ph.D. for — Your Universe Online

Supernovae are important astronomical objects. They tell us about how stars die and are used as measuring sticks to investigate distant galaxies. But there is still some uncertainty as to how the supernova process proceeds in some cases.

It is believed that the most common progenitor of Type II supernova is the collapse of supergiant stars. In this phase of their evolution stars oscillate between red supergiant and more compact blue supergiant stars. But as they pass between these states, they briefly become yellow supergiants.

Supernova events are thought to arise during either the blue or red supergiant phases. Yet, in 2011 an event known as SN 2011dh was spotted in the galaxy M51. This particular supernova was spotted in a position coincident with a yellow supergiant — inconsistent with previous physical models.

Based on this result, the Bersten team at the Kavli Institute for the Physics and Mathematics of the Universe found that when in a binary system a yellow supergiant star could produce a supernova such as SN 2011dh.

Archival Hubble data confirms the presence of the yellow supergiant at the location of the supernova, but the companion star is most likely a blue supergiant based on the team´s calculations. Such a star would radiate primarily in the ultraviolet, and would not have a significant flux in the optical. As a result the object would be masked by the yellow supergiant in the Hubble images of the region pre-supernova.

However, once the supernova brightness dies down, the relatively low luminosity of the companion could be resolved, if present. Planned observations of the system in 2014 should be able to resolve the companion and confirm the model proposed by the Bersten team.