Gruber Cosmology Prize 2007

In 2007 the prize was presented to Saul Perlmutter and Brian Schmidt and their teams: the Supernova Cosmology Project and the High-z Supernova Search Team, independently discovered that the expansion of the Universe is accelerating. Their discovery led to the idea of an expansion force, dubbed dark energy. And it suggested that the fate of the universe is to just keep expanding, faster and faster.

Saul Perlmutter and Brian Schmidt

An accelerating universe was a crazy result that was hard to accept. Yet, two teams, racing neck and neck, simultaneously came to the same conclusion. Their discovery led to the idea of an expansion force, dubbed dark energy. And it suggests that the fate of the universe is to just keep expanding, faster and faster.

The two teams expected to find that the universe would either expand then contract, or it would expand for ever but slowing over the millennia. But there were a growing number of hints that all was not right with the theories of the time.

To find out, they not only needed to be able to measure the speed with which distant objects are traveling away from us, but also how far away they are. And to do this they needed standardized light sources — very bright ones that would be visible to Earth-based telescopes despite being billions of light years away and billions of years old.

The standard light sources they used were exploding stars — in particular Type Ia supernovae. But finding them wasn’t easy. Then the analyses over the results turned up very surprising results. “The data wasn’t behaving as we thought it would,” says Schmidt. “There was a lot of nervous laughter,” says Perlmutter. For both teams it was not what they were expecting. For months they both tried to figure out where they had gone wrong, searching for any tiny source of error. But the data was right. The accepted model of the universe was wrong.

Today Perlmutter, Schmidt and their colleagues continue to explore the implications of their work. Schmidt is planning the SkyMapper project, a telescope to map the southern sky. Perlmutter is working on a satellite mission that would study supernovae and the nature of dark energy.

The $US500,000 prize will be shared in four parts: by Schmidt — at the Australian National University; Saul Perlmutter — at the University of California, Berkeley; and the fifty-one co-authors of the key papers (Saul Perlmutter and the Supernova Cosmology Project Team from Australia, Chile, France, Spain, Sweden, UK and USA; and for the High-z Supernova Search Team: Brian Schmidt and his team from the USA, UK, Germany, Chile and Australia).

The key papers reporting their discoveries were Riess et al., 1998, AJ, 116, 1009, "Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant"

Perlmutter et al. 1999, ApJ, 517, 565, "Measurements of Omega and Lambda from 42 High-Redshift Supernovae"

More information about this award can be found here.


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International Year of Astronomy