Two scientists from the United States and one from Australia have won the 2011 Nobel Prize in Physics, the Royal Swedish Academy of Sciences announced Tuesday.
Half of the award went to Saul Perlmutter from Lawrence Berkeley National Laboratory and University of California, Berkeley. The other half went to Brian P. Schmidt of Australian National University and Adam G. Riess of Johns Hopkins University and the Space Telescope Science Institute.
The prize in physics is worth 10 million Swedish kronor (about $1.44 million).
Scientists had known for a while that the universe is expanding because of the Big Bang about 14 billion years ago. However, the two teams that won this year's prize discovered that the universe's expansion was accelerating. They did so by studying a type of exploding star, called supernova.