The 2019 Nobel Prize in Physics

Credit: Nobel Institute

On October 8, the 2019 Nobel Prizes in Physics were announced. This year, there were three recipients: Swiss astrophysicists Michel Mayor and Didier Queloz, and Canadian physicist James Peebles. Peebles will receive one half of the associated monetary prize, and Mayor and Queloz will split the other half.

Michel Mayor and Didier Queloz are being recognized for one of the most revolutionary discoveries in modern astronomy: the detection of the first exoplanet orbiting a main sequence star. The planet 51 Pegasi b, also known as Dimidium, was discovered in 1995 around the star 51 Pegasi 47.9 lightyears from Earth using the radial velocity method. It had a mass of around 146 Earth masses and orbited its host star in 4.23 days. This discovery proved to the scientific community and the world at large that planets exist beyond the solar system. Since then, exoplanetary astronomy has experienced a massive boom in research, resulting in over 4,000 known exoplanets.

51 Pegasi b is a significant discovery not just because it demonstrated that exoplanets exist, but because it showed astronomers that exoplanetary systems will vary greatly from our own. 51 Pegasi b is the only planet in its system, and it is a Jupiter-sized planet that orbits its star very closely. Comparing this to our own eight-planet system, where the closest gas giant to the Sun takes 12 years to orbit the Sun, this system is in stark contrast to our own. 51 Pegasi b is the original “hot Jupiter”, a class of planet that further research has shown is one of the most common types of exoplanet. This discovery paved the way for the exoplanetary astronomy of today, which will hopefully culminate in the discovery of truly habitable worlds, and perhaps extraterrestrial life, sometime in the future.

James Peebles is being recognized for his ground-breaking contributions to theoretical studies in physical cosmology. Once, physical cosmology was not considered a serious or rigorous branch of physics. However, thanks to the work of physicists such as Peebles, it is now our best tool for understanding how the origins and eventual fate of the universe. He has been previously recognized by the Shaw Prize, whose citation for Peebles stated that he transformed “a highly speculative field into a precision science."

Peebles made significant contributions to the Big Bang model, our current theory which describes the origin of the universe. He also predicted several ways in which the Big Bang model could be experimentally supported, such as the cosmic microwave background (CMB). He made further significant contributions to big bang nucleosynthesis, models of the formation of large-scale structure in the universe, and the ever-mysterious dark matter and dark energy. The significance of Peebles’ career cannot be understated, as thanks to his work, we have an exceptional understanding of the origin and evolution of the universe. Studies in physical cosmology will ideally lead to, sometime in the future, a complete understanding of dark matter and dark energy; this would be a grand triumph in our quest to understand reality.