The Oldest Stars in the Universe

The very first stars formed just ~200 million years after the Big Bang, some 13.5 billion years ago. Have any of them survived to the present day and if so can we find them here in our own Milky Way?     The first stars were likely quite different from typical stars of today, in particular it is theoretically predicted that most of them were quite massive, 10-200 solar masses or even more. This would mean that they died in spectacular supernova explosions very quickly, enriching the surrounding interstellar medium from which the next generation of stars formed. It is thus possible to study the still very poorly understood nature of these enigmatic stars in three ways: 1) observe this cosmic epoch at extremely high redshift using e.g. the Hubble Space Telescope and soon the James Webb Space Telescope; 2) find one of the exceptionally rare surviving first stars of low mass (<1 solar mass, thus with lifetimes >13 billion years) possibly lurking in our Milky Way neighborhood; or 3) to determine the chemical compositions of the second generation stars which contain the nucleosynthetic fingerprints of the first stars. At ANU we are world-leaders in the last two efforts even if no true first star has yet been found. The study of the first stars and their impact on the cosmos is one of the major challenges in modern astrophysics and cosmology, which is driving much of the development of the next generation of ground-based and space-based telescopes, both in the optical and radio.

At ANU we have a competitive advantage with the new SkyMapper telescope, which enables us to efficiently identify extremely old stars in the Galaxy due to their characteristic colours as they contain very little, if any, elements heavier than helium. Once identified, we obtain spectra of these stars using telescopes at Siding Spring Observatory and overseas, including Keck (Hawaii), VLT and Magellan (both in Chile) to determine their detailed elemental abundance patterns. We concentrate our search for the first stars in the Milky Way halo and, more recently, in the bulge and nearby dwarf galaxies, where the oldest stars are predicted to preferentially reside today.

We are looking for ambitious students keen to join the project. They can be involved in different aspects, both observational (e.g. optimising the SkyMapper target selection, spectroscopic confirmation and characterisation of the most interesting stars) and theoretical/computational (e.g. improving how stellar spectra are analysed, determining ages of halo and bulge stars from asteroseismology with the Kepler satellite). 

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Updated:  25 November 2017/Responsible Officer:  RSAA Director/Page Contact:  Webmaster