Different stellar demise

Abstract

A decades-old theory of stellar evolution — that the most massive stars end their life in a peculiar type of explosion termed a pair-instability supernova — finally seems to have been confirmed by observations. Stars like the Sun end their stellar lives as white dwarfs. Theory predicts a different fate for stars with masses over 140 times that of the Sun (if they exist, which they don't in the Milky Way). When they have evolved to the stage of having oxygen cores the pressure-supporting photons turn into electron–positron pairs, absorbing energy and letting the core collapse to produce a 'pair instability' supernova. Analysis of the spectrum and light curve of supernova 2007bi, a luminous event in a nearby dwarf galaxy, provides evidence of such an explosion. The SN 2007bi progenitor is estimated to have had a core of greater than 100 solar masses. Calculations point to an explosion producing more than three solar masses worth of radioactive nickel-56, in line with what would be expected from a massive oxygen core. The implication is that there are extremely massive stars in the local Universe that could provide astronomers with a close-up of the type of star that may have dominated the early Universe.