Stockholm: Three US-born scientists won the Nobel Prize in physics on Tuesday for their studies of exploding stars that revealed that the expansion of the universe is accelerating.
The Royal Swedish Academy of Sciences said American Saul Perlmutter would share the 10 million kronor (USD 1.5 million) award with US-Australian Brian Schmidt and US scientist Adam Riess.
Working in two separate research teams during the 1990s - Perlmutter in one and Schmidt and Riess in the other – the scientists raced to map the universe's expansion by analysing a particular type of supernovas, or exploding stars.
They found that the light emitted by more than 50 distant supernovas was weaker than expected, a sign that the universe was expanding at an accelerating rate, the academy said.
"For almost a century the universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago," the citation said. "However the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the universe will end in ice."
Perlmutter, 52, heads the Supernova Cosmology Project at the University of California, Berkeley. Schmidt, 44, is the head of the High-z Supernova Search Team at the Australian National University in Weston Creek, Australia. Riess, 42, is an astronomy professor at Johns Hopkins University and Space Telescope Science Institute in Baltimore, Maryland.
Schmidt said he was just sitting down to have dinner with his family in Canberra, Australia, when the phone call came from the academy.

"I was somewhat suspicious when the Swedish voice came on," Schmidt said. "My knees sort of went weak and I had to walk around and sort my senses out."
The academy said the three researchers were stunned by their own discoveries - they had expected to find that the expansion of the universe was slowing down. But both teams reached the opposite conclusion: far-away galaxies were racing away from each other at an ever-increasing speed. The acceleration is believed to be driven by dark energy, one of the great mysteries of the universe.
The physics prize was the second Nobel to be announced this year. On Monday the medicine prize went to American Bruce Beutler and French scientist Jules Hoffmann who shared it with Canadian-born Ralph Steinman for their discoveries about the immune system. Steinman died three days before the announcement.
The prestigious Nobel Prizes were established in the will of Swedish industrialist Alfred Nobel, and have been handed out since 1901.
Last year's physics award went to Russian-born scientists Andre Geim and Konstantin Novoselov for groundbreaking experiments with graphene, the strongest and thinnest material known to mankind.
The prizes are handed out every year on December 10, on the anniversary of Nobel's death in 1896.

No surprise if an Indian bags Literature Nobel: Satchidanandan

Meanwhile, seasoned Malayalam poet K Satchidanandan, who has been writing for over 40 years, says there is a wealth of writing in Indian languages that has not yet been discovered outside the country due to which it loses out on big literary prizes such as the Nobel.
Satchidanandan along with Vijaydan Detha, a octogenarian short story writer hailing from Rajasthan figure among probables for this year's Nobel Prize for Literature, that is likely to be announced on Thursday, October 6.
British online site Ladbrokes has tipped Detha and Satchidanandan along with Swedish poet Tomas Transtroemer, Japanese novelist Haruki Murakami, Australia's Les Murray, Kenya's Ngugi wa Thiong'o, Somalia's Nuruddin Farah, Hungary's Peter Nadas, Korean poet Ko Un and China's Bei Dao as probable contestants shortlisted by the highly secretive Prize.
"I think writers in India are versatile in the languages and consider some of them even better that many writers around the world and I would not think of it as strange if an Indian does bag the Nobel," Satchidanandan said from Kochi where he is currently attending a Sahitya Akademi poetry workshop.
The site is putting the odds on France-based Syrian poet Adonis who writes in Arabic to bag this year's 10 mn Swedish crown (USD 1.46 million) closely watched Nobel Literature.
"Adonis is a poet that I have always admired, he is an important voice in Arabic poetry. Another poet Transtroemer of Sweden is one of the finest poets also the Chinese poet Bei
Dao I know personally," says Satchidanandan.
Detha, popularly known as Bijji draws from the local folklore and dialects of Rajasthan and has over 800 short stories to his credit and his stories and novels have been adapted for plays and films including Habib Tanvir's "Charandas Chor" and Amol Palekar's "Paheli".

When contacted Detha says, "Anybody would feel nice to know that his name is being considered for the Prize which was won by Rabindranath Tagore."
"I used to write in Hindi when I started out initially but felt it is my responsibility to write in Rajasthani and promote the local dialects whenever I write," says the 85-year-old author who says his readers are always before him when he spins out his stories.
"I write short stories, novels and essays and write for the young as well as the old. Writing is an art which is honed with practice. I kept writing for my own magazine Lok Sanskriti and kept refining my writing" says the author.
Poet Satchidanandan says writing in English gets more visibility especially in the West. "I write in Malayalam but my works have been translated into Italian, French and even Arabic. I have attended many international festivals, but there are a lot of good writers in vernacular languages who remain unknown because they are not translated."
In 1913 Rabindranath Tagore became the first Indian to bag the Nobel for Literature. Rudyard Kipling, born in Mumbai, 1865 was awarded the Nobel for the same in 1907. In 2001 it went to V S Naipaul.
The Nobel Committee sends out invitation letters in September each year to 600-700 individuals and organisations qualified to nominate for the Nobel Prize in Literature. The statutes of the Nobel Foundation restrict disclosure of information about the nominations for 50 years.
Members of the Swedish Academy, Professors of literature and of linguistics at universities and university colleges, previous Nobel Laureates in Literature and presidents of those societies of authors that are representative of the literary production in their respective countries are qualified to submit proposals for the Nobel Literature Prize.
Last year the Literature prize went to Mario Vargas Llosa of Peru.