Deep Space Supernovas May Reveal If Universe Will Expand Forever

November 13, 1992

By Judith Goldhaber,

The discovery of exploding stars almost halfway to the edge of the universe may help scientists settle the question of whether the universe is infinite and will continue to expand forever or is finite and will eventually slow down, reverse direction, and contract to a point.

A team of LBL scientists working with scientists from the United Kingdom have reported the discovery of what they believe to be a "Type Ia" supernova in a galaxy estimated to be about five billion light years from the Earth. This is the most distant supernova ever observed. The recent spectacular Supernova 1987A was in a galaxy comparatively close to the Milky Way--two hundred thousand light years away or less.

The team of scientists was led by astrophysicists Saul Perlmutter, Carl Pennypacker, and Gerson Goldhaber of LBL's Physics Division.

The scientists first observed the supernova on April 28, 1992, and watched it until it faded from sight after about a month. It took many months of checks and cross-checks before they had eliminated possible sources of error and satisfied themselves that they were indeed looking at a supernova.

Perlmutter commented, "The distance of this supernova in light years corresponds roughly to the age of the solar system-- estimated as four and a half billion years. That means that the light from this supernova began its journey just about the time the Earth was being formed."

The scientists are planning to use the light from this supernova--and from others like it--to make a precise measurement of its distance from Earth and the velocity at which it is receding in the expanding universe. Type Ia supernovas, no matter where they occur in the universe, are believed to give off about the same amount of light. Since their brightness is a constant, such supernovas can serve as reliable indicators of distance in deep space. From this information, the scientists say it may be possible to determine if the universe is infinite universe or finite.

The supernova discovery was made as part of an international collaboration at the Isaac Newton telescope in La Palma, Canary Islands, Spain, by a team of astronomers and astrophysicists from LBL; the Space Sciences Laboratory and the Center for Particle Astrophysics at UC Berkeley; the Royal Greenwich Observatory and the Institute of Astronomy, Cambridge University, England; and Durham University, England.

A new system to observe supernovas is now being designed--a collaborative effort by the same international group. When it is operating, the team hopes to find additional distant supernovas at the rate of several per night of viewing. Scientists estimate that Type 1a supernovas occur at the rate of about one every 500 years per galaxy, and the supernova search will scan close to one third of a million galaxies.