Uploaded April 2025 | Updated September 2026, 18 hours ago
Searching for the Origin of the Highest Particles in Nature
Cosmic rays are nuclei of the common elements that have been accelerated to high energies, the greatest of which match the energy of tennis balls hit by Andy Murray. Discovered in 1912, they are the most energetic particles in nature and must have been created in some of the most violent regions in the Universe. At energies above about 1014 eV, the flux of the primary particles is too low for observations with instruments on balloons or satellites. Instead, information about them is obtained by studying the extensive air showers that they create in the atmosphere, and which produce a footprint, spread over several square kilometre at ground level, containing billions of secondary particles. The most energetic particles are very rare, and one device constructed to study the showers that they produce is the Pierre Auger Observatory in Argentina. It has an area of 3000 km2, about the size of West Yorkshire, and is the largest cosmic ray detector ever built. The techniques used to measure these rare events will be described and the latest results from the observatory, which have transformed our knowledge of these rare events and of their origin, will be discussed.
The talk provides a background to the overview presented in an article in Astronomy & Geophysics, October 2024.
Speaker Biography:
Alan Watson was an undergraduate and postgraduate in the Department of Natural Philosophy (Physics) at the University of Edinburgh. After completing his PhD on the Condensation of Water Vapour in 1964, he took up a lectureship at the University of Leeds where he began studying high-energy cosmic rays. He was involved in the construction of an array of water-Cherenkov detectors that covered an area of 12 km2 at Haverah Park, near Harrogate, and was operated until 1987.This array was the premier source of data on cosmic rays above 1017 eV for many years. After closure of the Haverah Park facility, his group worked at the South Pole searching for gamma-rays from the supernova SN1987A. In 1991, he and the Nobel Laureate Jim Cronin (University of Chicago) developed an international collaboration of ~350 scientists from 18 countries to create the Pierre Auger Observatory in Argentina with the aim of measuring the properties of the highest energy cosmic rays with unprecedented precision. Watson has been a Fellow of the Institute of Physics and the Royal Astronomical Society for many years and was elected to the Royal Society in 2000. He gave the Royal Astronomical Society’s George Darwin lecture in 2008 and was awarded the Faraday Gold Medal of the Institute of Physics in 2011. Watson is an Emeritus Professor at the University of Leeds and Spokesperson Emeritus of the Pierre Auger Observatory.
ras.ac.uk/events-and-meetings/friends-ras/friends-ras-only-lecture-searching-origin-highest-particles-nature
Searching for the Origin of the Highest Particles in Nature
Cosmic rays are nuclei of the common elements that have been accelerated to high energies, the greatest of which match the energy of tennis balls hit by Andy Murray. Discovered in 1912, they are the most energetic particles in nature and must have been created in some of the most violent regions in the Universe. At energies above about 1014 eV, the flux of the primary particles is too low for observations with instruments on balloons or satellites. Instead, information about them is obtained by studying the extensive air showers that they create in the atmosphere, and which produce a footprint, spread over several square kilometre at ground level, containing billions of secondary particles. The most energetic particles are very rare, and one device constructed to study the showers that they produce is the Pierre Auger Observatory in Argentina. It has an area of 3000 km2, about the size of West Yorkshire, and is the largest cosmic ray detector ever built. The techniques used to measure these rare events will be described and the latest results from the observatory, which have transformed our knowledge of these rare events and of their origin, will be discussed.
The talk provides a background to the overview presented in an article in Astronomy & Geophysics, October 2024.
Speaker Biography:
Alan Watson was an undergraduate and postgraduate in the Department of Natural Philosophy (Physics) at the University of Edinburgh. After completing his PhD on the Condensation of Water Vapour in 1964, he took up a lectureship at the University of Leeds where he began studying high-energy cosmic rays. He was involved in the construction of an array of water-Cherenkov detectors that covered an area of 12 km2 at Haverah Park, near Harrogate, and was operated until 1987.This array was the premier source of data on cosmic rays above 1017 eV for many years. After closure of the Haverah Park facility, his group worked at the South Pole searching for gamma-rays from the supernova SN1987A. In 1991, he and the Nobel Laureate Jim Cronin (University of Chicago) developed an international collaboration of ~350 scientists from 18 countries to create the Pierre Auger Observatory in Argentina with the aim of measuring the properties of the highest energy cosmic rays with unprecedented precision. Watson has been a Fellow of the Institute of Physics and the Royal Astronomical Society for many years and was elected to the Royal Society in 2000. He gave the Royal Astronomical Society’s George Darwin lecture in 2008 and was awarded the Faraday Gold Medal of the Institute of Physics in 2011. Watson is an Emeritus Professor at the University of Leeds and Spokesperson Emeritus of the Pierre Auger Observatory.
ras.ac.uk/events-and-meetings/friends-ras/friends-ras-only-lecture-searching-origin-highest-particles-nature
