The line points to a supernova in a relatively nearby galaxy. Photographed by the Palomar 60-inch telescope.
A Type Ia supernova explosion is produced in a special kind of binary star system. The system is one where a hot, small (Earth sized),
dead core of a star known as a white dwarf is in orbit with a giant star. It is thought that the white dwarf pulls the outer portions off of
the giant star until enough material accumulates and eventually detonates the entire white dwarf star.
The resulting explosion can be seen far across the universe. Since Type Ia supernovae always reach the same maximium brightnesses, they can
be used to help determine the distance to the galaxies in which they have been found. Observations of these supernovae, made here at the
Palomar Observatory, have helped astronomers to determine that the universe is accelerating its rate of expansion as it ages.
