Monthly Archives: April 2014
Astronomers determine a supernova’s type in part by its spectrum and in part by its light curve, a graph of brightness changes. The energy driving a supernova’s rapidly expanding gas comes mainly from three means: the radioactive decay of freshly synthesized elements, typically nickel-56; the shock wave heating the star’s extended hydrogen atmosphere, if present; and the interaction between the supernova’s ejecta and any hydrogen gas in the vicinity.
Massive stars are fascinating objects, and I like to call them the “queens” of the stars because they truly rule all aspects of life in every galaxy. They eject huge quantities of material throughout their lives in flows called stellar winds. The exact properties of such winds still remain uncertain, with values for the rates of mass-loss differing by up to two orders of magnitude.
Cosmic rays — extremely high-energy particles from space — were first discovered in 1912. Over time, scientists have found that some 90 percent of those particles are protons while the remaining 10 percent are electrons and other atomic nuclei. But they lacked direct evidence of the process that accelerates these particles to such extreme energies.