Three Win Physics Nobel for Showing Our Place in the Cosmos

Half goes to cosmologist James Peebles for work on cosmic background and dark matter and half goes to the team that discovered the first exoplanet

Physics Nobel
James Peebles, Michael Mayor and Didier Queloz Copyright © Nobel Media 2019. Illustration: Niklas Elmehed

Yesterday, the Nobel Prize in Physics was awarded to three scientists responsible for mapping out Earth’s place in the cosmos.

The award honors two separate achievements. James Peebles, professor emeritus at Princeton University, is receiving a half-share of the award for his pioneering theoretical work in cosmology, which helped researchers establish the structure of the universe. He also proposed the idea that the majority of the universe is made of cold dark matter and is filled with dark energy, neither of which researchers are currently able to detect.

Michael Mayor of the University of Geneva and Didier Queloz of the University of Geneva and Cambridge University will each receive a quarter share of the prize for their 1995 announcement of the first discovery of planet outside our own solar system.

“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,” Ulf Danielsson of the Royal Swedish Academy of Sciences said while announcing the winners. “Our view of our place in the universe will never be the same again.”

Michael Turner of the University of Chicago and the Kavli Foundation tells the New York Times' Kenneth Chang and Megan Specia that Peebles has been a leader in almost all of the key discoveries in cosmology for over 50 years. “Jim has been involved in almost all of the major developments since the discovery of the cosmic microwave background in 1965 and has been the leader of the field for all that time,” he says.

CalTech physicist Sean Carroll tells the Associated Press' Seth Borenstein and David Keyton that Peebles' win is likely the first Physics Nobel awarded for purely theoretical cosmology. In the past, most astronomy awards have been for observations of cosmic phenomenon. But Peebles work and the tools he created enabled much of the work that has taken place in the last half century.

In the 1960s, what cosmologists knew about the universe was rudimentary, the Times reports. Cosmologists didn’t know how far away objects were, how old the universe was, or how it is structured. Most ideas were just guesses that varied from scientist to scientist.

Peebles wasn’t satisfied with that, and he worked to find ways to answer those big questions. In 1964, researchers discovered the cosmic background radiation, something Peebles and his colleagues had predicted. The radiation is a remainder from the early days of the universe and pervades the entire universe with almost constant radiation. Peebles also predicted that by studying minute variations in the background radiation, astronomers could find areas of the universe where matter was clumped together. That eventually allowed astronomers to begin to outline the structure of the universe, which is made of filaments of stars, galaxies and clusters of galaxies.

In the 1980s, he added dark matter to the mix, which would explain why galaxies clumped together despite their lack of visible mass. He also proposed that the universe was likely expanding, and that expansion was accelerating due to the force of dark energy.

In the 1990s, Peebles' theories were confirmed, slowly but surely, by advancing technology. Researchers found that fluctuations in the background radiation did correspond to clumps of matter. In 1998, astronomers confirmed that the universe is expanding and accelerating. Dark matter and dark energy, however, are still unexplained, but researchers are diligently researching the concepts.

The other half of the Nobel is more traditional. In the early 1990s, astronomers despaired at finding planets orbiting other stars. Despite a quarter century of trying, they had not located any—except for a few circling an exploded star. Some researchers began to believe that most stars formed without planets, and that planets were exceedingly rare.

But in 1995, Didier Queloz, then a graduate student working with Mayor, wrote software that looked for tiny wobbles in the light and color of stars. That would be an indication that the gravity of an orbiting planet was affecting the star, shifting the wavelengths of light.

After observing 20 bright stars, the software detected a wobble in the star 51 Pegasi, 51 light years away. It took six months for Queloz to believe his data and longer for Mayor to be convinced. But in October 1995, the duo announced that they had found the first true exoplanet, a Jupiter-sized planet around 51 Pegasi.

The find set off a revolution in astronomy. Since then new teams have discovered over 4,000 exoplanets in the Milky Way of all sizes, compositions and orbiting various types of stars. That was “the first step in our search for" other life in the universe, astronomer Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University, tells the AP.

Queloz, for one, was shocked by his win. “When we made the discovery, very early on lots of people told me that will be a Nobel Prize discovery. For 25 years, people kept saying this and at some point I just said this isn’t going to win a Nobel Prize after all,” he tells Agence France Presse.

Peebles, too, was elated with the prize, with the AP noting that the eminent comosologist, 84, couldn’t stop giggling during a phone interview on the morning of the announcement.

The prize will be awarded on December 10, the anniversary of Alfred Nobel's death.