Nobel Prize in Physics Awarded to Trio for Advances in Cosmology

By Robert Lee Hotz and Joanna Sugden (WSJ)

Updated Oct. 8, 2019 10:40 am ET

James Peebles, Michel Mayor and Didier Queloz were awarded the prize for work advancing knowledge of the Earth’s place in the universe

A U.S. cosmologist and two Swiss astronomers shared the Nobel Prize in physics on Tuesday, for insights into the evolution of the universe and the discovery that other worlds circle stars far from our own solar system.

The Royal Swedish Academy of Sciences, which chooses the Nobel laureates, awarded one half of this year’s physics prize to James Peebles at Princeton University “for theoretical discoveries in physical cosmology,” and the other half jointly to Michel Mayor and Didier Queloz at the University of Geneva “for the discovery of an exoplanet orbiting a solar-type star,” said Goran Hansson, the academy’s secretary-general.

Each scientist will receive a gold medal, a diploma and a share of $908,000 in cash.

The prize honored both scientific theory and practical observation, several physicists said. Taken together, the work of the three scientists encompasses the entire known history of the cosmos: from the first sparks of light after the Big Bang some 14 billion-or-so years ago through the proliferation of planets around almost every star in the universe today.

“It is not only about the universe but about us and our place in that bigger canvas,” said Robbert Dijkgraaf, director of the Institute for Advanced Study in Princeton, N.J., who wasn’t involved in the award. “It answers the existential questions of where did it all come from and what is it made of. The big lesson is that our solar system is not unique.”

Starting as a graduate student in 1964, Canadian-born Dr. Peebles developed precise models of cosmic creation, transforming cosmology “from speculation to science,” the academy said.

When he began, there was little direct evidence of how the universe might have expanded into its current form. At the suggestion of his lab director, he studied observations of ancient light embodied in cosmic background radiation—itself the subject of a 1978 Nobel physics prize—and, step by step, calculated how the cosmos might have expanded into the stars, galaxies, dark matter and dark energy of the present-day universe.

That early radiation he analyzed was like a “baby photo” of the universe, he said.

“We have very clear evidence that our universe did expand from a hot, dense state, but although the theory is thoroughly tested, we still must admit that dark matter and dark energy are mysterious,” Dr. Peebles said. “Although we have made great advances in understanding the nature and evolution of our universe, there are still many open questions.”

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He never had a plan of discovery, he said. He followed where his ideas led. “I have an iconoclastic turn of mind,” he said. “The subject grew, and I grew with it. Progress was slow, halting at first. It speeded up. I started working on this 65 years ago. Where did all that time go?”

While Dr. Peebles labored to build a theory, Dr. Mayor and Dr. Queloz, who also work at the University of Cambridge in the U.K., searched for concrete evidence that creation had seeded planets beyond our own solar system. They searched for subtle shifts in starlight that would indicate a wobble caused by an orbiting planet.

“No one knew whether exoplanets existed or not,” Dr. Mayor recalled, in a statement. “For years prestigious astronomers had been looking for them in vain. Indeed, the technologies to enable such a discovery did not exist at the time.”

In 1995, using a new observatory instrument, they announced the discovery of a planet orbiting around another star called 51 Pegasi, named for the constellation of the flying horse Pegasus, about 51 light years from Earth. The Jupiter-sized planet orbits so closely to its star that its year lasts just 4 ½ days.

“This was a revelation that forever changed Earth’s place in the universe,” said physicist Mats Larsen, chairman of the academy’s physics committee.

As of last month, astronomers have discovered more than 4,000 exoplanets, as worlds around alien stars are called, with several thousand more awaiting formal confirmation. Astronomers have calculated that there could be as many as 40 billion Earth-sized planets orbiting Sun-like stars in the Milky Way.

Write to Robert Lee Hotz at sciencejournal@wsj.com and Joanna Sugden at joanna.sugden@wsj.com