A Search for Very Old Stars
September 20, 2010
Abstract: This seminar will describe a joint work by Vijay Mohan, Nando Patat, Ken Freeman and the speaker to look for stars around 20 Gyr old. The cosmological significance of such a search will be described first, including an alternative cosmology which allows arbitrarily old stars to exist. The search for old stars is carried out in the LMC and color magnitude diagrams of stars are used to estimate their ages. A group of stars possibly lying close to a subgiant branch of the CMD is identified as likely old stars. Alternative explanations of this group in terms of younger systems are discussed and seen to be rather contrived. Future tests are proposed to decide between these alternatives.