Forever slowing, it never quite comes to a rest. As befits a research project of this magnitude, the Supernova Cosmology Project is a global collaboration based at Berkeley Lab that involves researchers in Sweden, England, France, and Germany, and observatories that include the Keck and Hubble telescopes. The project began after Perlmutter devised a technique that uses a stellar beacon to reveal the universe's deceleration rate. Perlmutter came up with a way to find and analyze the ancients. His Supernova Cosmology Project uses telescopes to look deep into space, detecting and characterizing supernovae that exploded billions of years ago.
Researchers can ascertain the amount the universe has expanded since the time of each explosion.
But therein lies the rub. When a bright object is observed in the sky, it is hard to tell whether it is intrinsically bright or simply closer to us than a dimmer object. It turns out there is a way to resolve this. Supernovae are rare or commonplace, depending upon your point of view. Within a single galaxy, stars explode only a few times per millennium, but among the billions and billions of galaxies in the universe as a whole, a supernova occurs every few seconds.