Supernovae

Supernovae are exploding stars. These stellar explosions are responsible for creating all the elements heavier than iron and for distributing the elements synthesized throughout the star's lifetime to the interstellar medium. The CfA Supernova Group uses various telescopes (Mount Hopkins, MMT, Magellan) to study supernovae of all types, both in nearby and distant galaxies.

Supernovae come in two distinct physical flavors. Type Ia supernovae result from a thermonuclear runaway in a carbon and oxygen White Dwarf star that reaches a critical mass of 1.4 solar masses. With a peak luminosity of 9 billion times that of the Sun, Type Ia supernovae can be seen out to a sizeable fraction of the visible Universe, and hence serve as distance indicators on cosmological scales. The CfA Supernova Group has been instrumental in establishing the foundations of cosmology with Type Ia supernovae (see also The Accelerating Universe).

Supernovae also occur when massive stars run out of fuel to support their own weight. At this stage the star's dense iron core collapses and then bounces, driving a powerful shock wave which unbinds the star. The CfA Supernova Group has used these "core-collapse" supernovae both as extragalactic distance indicators (Type II supernovae), to probe the connection between Type Ib/c supernovae and gamma-ray burstsm and to understand the various conditions under which very massive stars die.