Canadian-American cosmologist James Peebles and Swiss astronomers Michel Mayor and Didier Queloz on Tuesday won the Nobel Physics Prize for research that increases the understanding of our place in the Universe.

Peebles won one-half of the prize "for theoretical discoveries that have contributed to our understanding of how the Universe evolved after the Big Bang," professor Goran Hansson, secretary general of the Royal Swedish Academy of Sciences, told a news conference.

Nobel Physics Prize winners
The trio won the Nobel Physics Prize for research increasing our understanding of our place in the universe Photo: AFP / Jonathan NACKSTRAND Jonathan Nackstrand/AFP

Mayor and Queloz shared the other half for the first discovery, in October 1995, of a planet outside our solar system -- an exoplanet -- orbiting a Sun-like star in the Milky Way.

"Their discoveries have forever changed our conceptions of the world," the jury said.

Developed over two decades since the mid-1960s, Peebles' theoretical framework is "the basis of our contemporary ideas about the Universe".

Peebles built upon Albert Einstein's work on the origins of the Universe by looking back to the millennia immediately after the Big Bang, when light rays started to shoot outwards into space.

Using theoretical tools and calculations, he drew a link between the temperature of the radiation emitted after the Big Bang and the amount of matter it created.

'Unknown matter'

His work showed that the matter known to us -- such as stars, planets, and ourselves -- only make up five percent of the universe, while the other 95 percent is made up of "unknown dark matter and dark energy".

Nobel Physics Prize winners
Peebles (L) shares the prize Mayor (C) and Queloz (R) for their research into the Universe Photo: SCANPIX SWEDEN / JESSICA GOW, Frank PERRY, ISABEL INFANTES Jessica Gow, Frank Perry, Isabel Infantes/Scanpix Sweden

In a telephone interview, Peebles said that what those elements actually are is still an open question.

"Although the theory is very thoroughly tested, we still must admit that the dark matter and dark energy are mysterious," Peebles said.

Nobel Physics Prize winners
Mini-profiles of the winners of the Nobel prize for physics 2019: James Peebles (Canada-US) and and Michel Mayor and Didier Queloz (Switzerland). Photo: AFP / Cecilia SANCHEZ Cecilia Sanchez/AFP

Speaking at Princeton University later, he added that his ideas were not the "final answer."

"We can be very sure that as we discover new aspects of the expanding and evolving universe, we will be startled and amazed once again," he said.

Peebles, 84, is Albert Einstein Professor of Science at Princeton University in the United States, while Mayor, 77, and Queloz, 53, are professors at the University of Geneva. Queloz also works at the University of Cambridge in Britain.

Using custom-made instruments at their observatory in southern France in October 1995, Mayor and Queloz were able to detect a gaseous ball similar in size to Jupiter, orbiting a star 50 light years from our own Sun.

Harnessing a phenomenon known as the Doppler effect, which changes the colour of light depending on whether an object is approaching or retreating from Earth, the pair proved the planet, known as 51 Pegasus b, was orbiting its star.

Nobel Physics Prize winners
The discoveries of the 2019 Nobel physics laureates: how the universe evolved after the Big Bang and the first planet orbiting a solar-type star outside our solar system Photo: AFP / AFP

'Tip of the iceberg'

"Strange new worlds are still being discovered," the Nobel jury noted, challenging our preconceived ideas about planetary systems and "forcing scientists to revise their theories of the physical processes behind the origins of planets".

Mayor was a professor at Geneva University and Queloz was his doctorate student when they made their discovery which "started a revolution in astronomy," and since then over 4,000 exoplanets have been found in our home galaxy.

"What we detected 25 years ago was just the tip of the iceberg," Queloz told AFP.

"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 said.

The prize consists of a gold medal, a diploma and the sum of nine million Swedish kronor (about $914,000 or 833,000 euros).

The trio will receive the prize from King Carl XVI Gustaf at a formal ceremony in Stockholm on December 10, the anniversary of the 1896 death of scientist Alfred Nobel who created the prizes in his last will and testament.

In 2018, the honour went to Arthur Ashkin of the US, Gerard Mourou of France and Donna Strickland of the US for laser inventions used for advanced precision instruments in corrective eye surgery and in industry.

This year's Nobel season kicked off on Monday with the Medicine Prize awarded to Americans William Kaelin and Gregg Semenza, and Britain's Peter Ratcliffe.

They were honoured for research into how human cells sense and adapt to changing oxygen levels, which opens up new strategies to fight such diseases as cancer and anaemia.

The winners of this year's Chemistry Prize will be announced on Wednesday.

On Friday the action moves to Norway where the Peace Prize is awarded, with bookies backing Swedish teen climate activist Greta Thunberg.

The Economics Prize wraps up the Nobel season on Monday, October 14.

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