On October 8, the 2019 Nobel Prize in Physics was awarded jointly to James Peebles, Michel Mayor, and Didier Queloz “for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos”.  

James Peebles of Princeton University received half the prize, which was given to him “for theoretical discoveries in physical cosmology”. As one of the founders of physical cosmology as a research field, it is quite appropriate that he receive the award for his contributions to the subject. In the early 1960s, Peebles was among the first physicists to make precise calculations describing cosmological observations. 

One of his early achievements was calculating the temperature of the cosmic microwave background, the ambient radiation in the cosmos left over from the big bang.  Another significant contribution by Peebles was his calculation of the quantity of light elements like helium produced in the early stages of the universe; a process known as big bang nucleosynthesis. This work has profound implications for how the universe evolved, and how planets like Earth came to be.

In contrast to the large-scale cosmological work of Peebles, Michel Mayor and Didier Queloz of the University of Geneva received their share of the prize “for the discovery of an exoplanet orbiting a solar-type star”. In 1995, the pair observed a planet orbiting the star 51 Pegasi, a star similar to Earth’s own sun 50 lightyears away. This was the first observation of a planet orbiting a star outside of the solar system. 

The planet, called 51 Pegasi b, was a gas giant similar in characteristics to Jupiter, and was found by measuring the altered motion of the star as the planet’s gravity pulled it around. To date, 4,122 exoplanets have been discovered. While awarded for two developments which are not directly related, this year’s Nobel Prize in Physics showcased impressive contributions to both theoretical and observational astrophysics and cosmology which gave us a greater understanding of our universe and our place within it. 


Patrick Wong – Science Writer