Supernovae

Background

Supernovae are star explosions creating the greatest fireworks in the universe with a typical brightness that easily outshines whole galaxies. The last supernova in our galaxy occurred in 1604 (Kepler's star) and could be observed with the naked eye even during daylight.

Cassiopeia A supernova remnant. more

However, supernovae are frequently observed in other galaxies using large telescopes. Supernovae are key to understanding the origin of the elements in the universe — the majority of atoms on earth were at some point ejected in a supernova explosion.

Supernovae occur when a star runs out of fuel and cannot maintain the pressure needed to prevent a collapse due to gravity. However, we still don't understand how a collapsing star can result in an explosion ejecting matter outward. The basic idea is that the collapsing core forms a neutron star, which suddenly stops the collapse. The resulting bounce triggers the explosion of the remaining stellar material. Neutron stars have been observed in the remnants of ancient supernova explosions. But, while scientists run a lot of interesting supernova models, these models have one common problem: they do not explode.

The Role of NSCL

NSCL contributes towards the understanding of supernova explosions by providing data on the nuclear reactions that initiate the collapse of the stellar core and determine its speed. For example, nuclear theorists predicted that the nuclei present in the stellar core capture surrounding electrons at significantly different rates than anticipated before. These calculations have to be verified by experiments. Many of the critical nuclei are unstable and cannot be studied by conventional experimental methods. However, these nuclei can, for a short time, be recreated at NSCL and studied in-flight using collisions with well chosen target nuclei. This provides the necessary data to test theories and to improve model calculations of supernovae.