This year’s Nobel Prize for Physics, announced on Tuesday, recognises research that helps us understand our place in the universe.
Canadian-American cosmologist James Peebles, 84, won one-half of the Prize for his theoretical work helping us understand how the universe evolved after the Big Bang. The other half went to Swiss astronomers Michel Mayor, 77, and Didier Queloz, 53, for their discovery of an exoplanet that challenged preconceived ideas about planets.
How the universe evolved
Modern cosmology assumes that the universe formed as a result of the Big Bang. In decades of work since the 1960s, Peebles used theoretical physics and calculations to interpret what happened after. His work is focused largely on Cosmic Microwave Background (CMB) radiation, which is electromagnetic radiation left over from the early universe once it had cooled sufficiently following the Big Bang.
Today, CMB can be observed with detectors. When it was observed for the first time in 1964 by radio astronomers Arnold Penzias and Robert Wilson —who would go non to be awarded the 1978 Physics Nobel — they were initially puzzled. They learnt later that Peebles had predicted such radiation.
Peebles and colleagues have correlated the temperature of this radiation with the amount of matter created in the Big Bang, which was a key step towards understanding how this matter would later form the galaxies and galaxy clusters. From their work derives our knowledge of how mysterious the universe is — just 5% known matter and the rest unknown, as dark matter (26%) and dark energy (69%).
The hunt for extraterrestrial life, if any exists, depends on finding habitable planets, mainly outside our Solar System. Today, exoplanets are being discovered very frequently — over 4,000 are known — which is remarkable progress from three decades ago, when not even one exoplanet was known. The first confirmed discoveries came in 1992, but these were orbiting not a star but the remains of one.
The planet discovered by Mayor and Queloz in 1995 is 50 light years away, orbiting the star 51 Pegasus that is similar to our Sun. Called 51 Pegasus b, the exoplanet is not habitable either, but it challenged our understanding of planets and laid the foundation for future discoveries. Using a spectrograph, ELODIE, built by Mayor and collaborators and installed at the Haute-Provence Observatory in France, they predicted the planet by observing the “Doppler effect” — when the star wobbles as an effect of a planet’s gravity on its observed light.
It is a gas giant comparable to Jupiter, yet it very hot, unlike icy cold Jupiter; 51 Pegagsus b is even closer to its star than Mercury is to our Sun. Until then, gas giants were presumed to be cold, formed a great distance from their stars. Today, it is accepted that these hot gas giants represent what Jupiter would look like if it were suddenly transported closer to the Sun. The discovery of the planet “started a revolution in astronomy”, as described in the official Nobel Prize website. “Strange new worlds are still being discovered… forcing scientists to revise their theories of the physical processes behind the origins of planets,” it said.