Astronomy Colloquium / Fall 2007

October 24

Dr. Nathan Smith

UC Berkeley

Precursors to supernova explosions and extraordinary deaths of very massive stars

I will discuss some observations of a few recent and extraordinary supernova explosions. Among these is SN2006gy, which radiated more luminous energy than any other supernova. It may be our first observed case of a so-called "pair instability supernova", thought to mark the deaths of the first stars in the very early Universe (although SN2006gy was relatively nearby), and it appears to have suffered a violent precursor mass ejection just 5-10 years before the SN. It was probably the most massive star ever seen to explode, and I will mention connections to one of the most massive stars in our own Milky Way galaxy, called Eta Carinae. SN2006gy is one of a class of supernovae that are plowing into very dense circumstellar matter ejected by the star in the decade or so preceding the final SN. Another example I will mention is SN2006jc, which was actually observed to have this type of eruption just 2 years before it exploded (the only such example so far). I will discuss how this episodic pre-supernova mass loss, combined with some other recent clues, is forcing us to revise some of our fundamental paradigms of massive star evolution.