This year’s Nobel Prize in Physics rewards new understanding of the Universe’s structure and history, and the first discovery of a planet orbiting a solar-type star outside our solar system.

A Canadian-American cosmologist and two Swiss scientists won this year's Nobel Prize in Physics on Tuesday for exploring the evolution of the universe and discovering a new kind of planet, with implications for that nagging question: Does life exist only on earth.

Canadian-born James Peebles, 84, an emeritus professor at Princeton University, won for his theoretical discoveries in cosmology. Swiss star-gazers Michel Mayor, 77, and Didier Queloz, 53, both of the University of Geneva, were honoured for finding an exoplanet — a planet outside our solar system — that orbits a sun-like star, the Nobel committee said.

“This year's Nobel laureates in physics have painted a picture of the universe far stranger and more wonderful than we ever could have imagined,”said Ulf Danielsson of the Royal Swedish Academy of Sciences, which selected the laureates. “Our view of our place in the universe will never be the same again.”

Cosmic radiation

Dr. Peebles, hailed as one of the most influential cosmologists of his time, who realized the importance of the cosmic radiation background born of the Big Bang, will collect one half of the 9 million kronor ($918,000) cash award. Dr. Mayor, who is an astrophysicist, and Dr. Queloz, an astronomer who is also at the University of Cambridge in Britain, will share the other half.

The Nobel committee said Dr. Peebles’ theoretical framework about the cosmos and its billions of galaxies and galaxy clusters amounted to “the foundation of our modern understanding of the universe's history, from the Big Bang to the present day.”

A clearly delighted Dr. Peebles chuckled repeatedly during a phone interview, recalling how he answered a 5:30 a.m. phone call from Stockholm thinking that “It’s either something very wonderful or it's something horrible.”

“I have a peaceful life,” he said. “It’s somehow now totally messed up!”

Dr. Mayor and Dr. Queloz were credited with having “started a revolution in astronomy” notably with the discovery of exoplanet 51 Pegasi B, a gaseous ball comparable with Jupiter, in 1995 — a time when, as Dr. Mayor recalled — “no one knew whether exoplanets existed or not.”

“Prestigious astronomers had been searching for them for years, in vain!” Dr. Mayor quipped.

The committee said more than 4,000 exoplanets have since been found in the Milky Way.

“Mayor and Queloz pioneered the path that will allow our generation to address one of the most exciting questions in science: Are we alone?” wrote Avi Loeb, chair of the Harvard University astronomy department, in an email.

“We now know that about a quarter of all stars have a planet of Earth’s size and surface temperature, with the potential of hosting liquid water and the chemistry of life on its surface,” he said.

Dr. Queloz was meeting with other academics interested in finding new planets when the press office at Cambridge University interrupted to tell him the big news: He had won the Nobel. He thought it was joke at first.

“I could barely breathe,” Dr. Queloz said.

Swedish academy member Mats Larsson said this year’s was “one of the easiest physics prizes for a long time to explain.”