2019 Nobel Prize in Physics

James Peebles, Michel Mayor and Didier Queloz were given the 2019 Physics Nobel Prize for ‘improving our understanding of evolution of universe and Earth’s place in the cosmos’James Peebles, born 1935 in Winnipeg, Canada. Ph.D. 1962 from Princeton University, USA. Albert Einstein Professor of Science at Princeton University, USA. Michel Mayor, born 1942 in Lausanne, Switzerland. Ph.D. 1971 from University of Geneva, Switzerland. Professor at University of Geneva, Switzerland. Didier Queloz, born 1966 in Geneva, Switzerland. Ph.D. 1995 from University of Geneva, Swit zerland. Professor at University of Geneva, Switzerland and University of Cambridge, UK. Half of the prize goes James Peebles “for theoretical discoveries in physical cosmology”, and the other half jointly to Michel Mayor and Didier Queloz “for the discovery of an exoplanet orbiting a solar-type star”. These scientists have transformed our ideas about the cosmos. While James Peebles’ theoretical discoveries contributed to our understanding of how the universe evolved after the Big Bang, Michel Mayor and Didier Queloz explored our cosmic neighbourhoods on the hunt for unknown planets.

The Peebles’ story James Peebles’ research laid a foundation for the transformation of cosmology over the last fifty years. His theoretical framework, developed since the mid-1960s, is the basis of our contemporary ideas about the universe. The Big Bang theory tells us that we have an expanding universe. The universe in the early stages of its evolution, almost 14 billion years ago, was much denser and hotter. It was a compact, hot and opaque particle soup. Since then, the universe has been expanding, becoming larger and colder. It took almost 400,000 years for expansion to cool this primordial soup to a few thousand degrees Celsius. The original particles combined to form a transparent gas that primarily consisted of hydrogen and helium atoms, and light was able to travel through space. Thus, 400,000 years after the Big Bang, the universe became transparent to light . Even today, this ancient radiation is all around us and, coded into it, many of the universe’s secrets are hiding. The expansion of space stretched the visible light waves so they ended up in the range of invisible microwaves, with a wavelength of a few millimetres. This is the cosmic microwave background radiation we have. Using his theoretical tools and calculations, James Peebles was able to interpret the traces from the infancy of the universe and discover new physical processes. A major breakthough came when James Peebles realised that the cosmic background radiation’s temperature could provide information about how much matter was created in the Big Bang, and understood that the release of this light played a decisive role in how matter could later clump up to form the galaxies and galaxy clusters that we now see in space. Peebles was rewarded for laying the foundation for modern cosmology, and also for his realisation that faint microwave radiation that filled the cosmos 400,000 years after the Big Bang contains crucial clues to what the universe looked like at this primitive stage and how it has evolved over the subsequent 13bn plus years. James Peebles’ theoretical framework, is the foundation of our modern understanding of the universe’s history, from the Big Bang to the present day. Peebles’ discoveries have led to insights about our cosmic surroundings, in which known matter comprises just fve per cent of all the matter and energy contained in the universe. The remaining 95 per cent is hidden from us as unknown dark matter and dark energy. Peebles is credited with developing the theoretical tools that allowed scientists to perform a cosmic inventory of what the universe is made from. The discovery of microwave radiation ushered in the new era of modern cosmology. The ancient radiation from the universe’s infancy has become a goldmine that contains the answers to almost everything cosmologists want to know. Scientists can fnd traces of the very frst moments of the universe in this radiation. With astounding accuracy, cosmologists led by Peebles were able to predict variations in the background radiation and show how they afect the matter and energy in the universe. James Peebles through his frst book, Physical Cosmology (1971), inspired a whole new generation of physicists to contribute to the subject’s development, not only through theoretical considerations but with observations and measurements. Dark matter and dark energy Since the 1930s scientists doubted that there could be more matter in the universe than that is known. Measurements of galaxies’ rotational speeds indicated that they must be held together by gravity from invisible matter, otherwise they would be torn apart. It was also thought that this dark matter played an important role in the origin of galaxies. The composition of dark matter remains one of cosmology’s biggest questions. In 1982, Peebles proposed that heavy and slow particles of cold dark matter could exist. We are still searching for these unknown particles of cold dark matter, which avoid interacting with already known matter and comprise 26 per cent of the cosmos. According to Einstein’s general theory of relativity, the geometry of space is intercon- nected with gravity – the more mass and energy the universe contains, the more curved space becomes. At a critical value of mass and energy, the universe does not curve. This type of universe, in which two parallel lines will never cross, is usually called fat. Measurements of cosmic background radiation, as well as theoretical considerations, clearly tell us that the universe is fat. However, the matter it contains is only enough for 31 per cent of the critical value, of which 5 per cent is ordinary matter and 26 per cent is dark matter. Most of it, 69 per cent, was missing. James Peebles in 1984, contributed to reviving Einstein’s cosmological constant, which is the energy of empty space. This has been named dark energy and flls 69 per cent of the cosmos. Along with cold dark matter and ordinary matter, it is enough to support the idea of a fat universe.

Michel Mayor and Didier Queloz Michel

Mayor and Didier Queloz have been recognised by the Swedish Academy for their joint discovery of the first exoplanet, 50 light years away in the constellation of Pegasus. The planet, 51 Pegasi b, is a gaseous ball about 150 times more massive than Earth and has a surface temperature of about 1,000C.In October 1995, Michel Mayor and Didier Queloz announced the first discovery of a planet outside our solar system, an exoplanet, orbiting a solar-type star in our home galaxy, the Milky Way. At the Haute-Provence Observatory in southern France, using custom-made instruments, they were able to see planet 51 Pegasi b. The pair discovered the exoplanet using a technique known as Doppler spectroscopy, which measures the tiny wobble of a star that occurs as the star-planet pair move around a common centre of gravity. This wobbling movement alternately blueshifts and redshifts the light from the star. When Queloz and Mayor set up the search it was with low expectations of finding anything because any planets massive enough to create a measurable Doppler shift were expected to have such long orbits that the wobble would take years to detect. Surprisingly, though, they found a huge planet sitting extremely close to its host star, with an orbit of just four days. This discovery started a revolution in astronomy and over 4,000 exoplanets have since been found in the Milky Way. These discoveries are forcing scientists to revise their theories of the physical processes behind the origins of planets. With numerous projects planned to start searching for exoplanets, we may eventually find an answer to the extraterrestrial life