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This year’s Nobel Prize in physics was awarded to three scientists who transformed our view of the cosmos, the Royal Swedish Academy of Sciences announced Tuesday.

James Peebles, a professor emeritus at Princeton University, shared half of the prize — and half of the prize money of more than $900,000 — for theories that explained how the universe swirled into galaxies and everything we see in the night sky, and indeed much that we cannot see.

The other half was shared by two Swiss astronomers, Michel Mayor and Didier Queloz, who were the first to discover an exoplanet, or a planet circling a distant sun-like star.

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“They really, sort of tell us something very essential — existential — about our place in the universe,” Ulf Danielsson, a member of the Nobel committee, said during an interview broadcast on the web.

Peebles, the Albert Einstein professor of science at Princeton, was not entirely taken by surprise by the early morning phone call from Stockholm.

“I have been working in cosmology for 55 years,” he said in an interview. “I’m the last man standing, so to speak, from those early days. It had crossed my mind.”

Mayor is an astrophysicist and professor emeritus of astronomy at the University of Geneva. He formally retired in 2007, according to the Planetary Society, but remains active as a researcher at the Geneva Observatory.

Queloz is a professor of physics at the Cavendish Laboratory at Cambridge University, and at the University of Geneva, where he works “at the origin of the exoplanet revolution in astrophysics.”

In the 1960s, when Peebles began studying the cosmos, knowledge about the universe was sparse and imprecise. Astronomers had observed stars, galaxies, clouds of gas, and other cosmic vistas through their telescopes, but struggled to explain much about them.

For example, cosmological distances were often just rough guesses, and estimates of the age of the universe varied widely.

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Peebles’ work helped place cosmology on a more solid, mathematical foundation.

“No one has done more to establish our current paradigm than Jim,” Michael Turner of the University of Chicago and the Kavli Foundation, a philanthropy that supports science, wrote in an email.

In 1964, two radio astronomers, Arno Penzias and Robert Wilson, discovered by accident a background hiss of microwaves pervading the universe. They were perplexed until they came across theoretical calculations by other scientists including Peebles.

Peebles and his colleagues had predicted this background radiation, a result of when the universe, about 400,000 years after the Big Bang, cooled off enough for hydrogen and helium atoms to form.

While the microwave background was almost uniform in all directions, reflecting a temperature of only a few degrees above absolute zero, it was not perfectly smooth. Peebles calculated that there should be faint fluctuations, and the fluctuations would reveal the places where matter had begun to clump together — the structure that would eventually be revealed as stars, galaxies, and clusters of galaxies.

In the early 1980s, Peebles became a proponent of the idea that the universe was filled with unseen “cold dark matter” — particles that did not interact with ordinary matter but whose gravitational pull formed galaxies and clusters of galaxies. A couple of years later, he added to his model a term that Albert Einstein had originally proposed and then discarded as his “biggest blunder.”

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Einstein had invented this idea, called the cosmological constant, to balance gravity and keep the universe static and unchanging. But astronomers established that the universe is actually expanding. Peebles used the cosmological constant, now known as dark energy, for a different reason — he aimed to show that the universe contained considerably less mass than was thought at the time.

The other half of this year’s physics Nobel goes to research that filled in a missing piece of the observable universe.

Astronomers had long presumed there must be planets in orbits around many other stars. But until a quarter century ago, they knew of none. Over the decades, claims of spotting planets evaporated upon closer examination.

In 1992, astronomers found the first planets outside the solar system — but those orbited an exploded star, making them an unlikely place for life to exist.

At the time, some astronomers were beginning to wonder if they would ever find planets.

“Maybe most stars don’t form with planets and our solar system is unusual and life is incredibly rare,” said Debra A. Fischer, a professor of astronomy at Yale University.

Three years later at the Haute-Provence Observatory in southern France, Mayor and Queloz successfully found a planet around 51 Pegasus, a star similar to our sun, 50 light years away. It was as large as Jupiter, and hugged its star in an orbit that took only four days. Although this broiling planet was not habitable, it pointed to how astronomers could now study planetary systems that could be similar to our own.

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“Completely transformative,” Fischer said of the discovery. “We are [in] the middle of a scientific revolution that people won’t appreciate until a hundred years go by.”