The CNO cycle is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction, which is more efficient at the Sun's core temperature. The CNO cycle is hypothesized to be dominant in stars that are more than 1.3 times as massive as the Sun.
The proton–proton chain, also commonly referred to as the p–p chain, is one of two known sets of nuclear fusion reactions by which stars convert hydrogen to helium. It dominates in stars with masses less than or equal to that of the Sun, whereas the CNO cycle, the other known reaction, is suggested by theoretical models to dominate in stars with masses greater than about 1.3 times that of the Sun.
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in a process called Big Bang nucleosynthesis. After about 20 minutes, the universe had expanded and cooled to a point at which these high-energy collisions among nucleons ended, so only the fastest and simplest reactions occurred, leaving our universe containing hydrogen and helium. The rest is traces of other elements such as lithium and the hydrogen isotope deuterium. Nucleosynthesis in stars and their explosions later produced the variety of elements and isotopes that we have today, in a process called cosmic chemical evolution. The amounts of total mass in elements heavier than hydrogen and helium remains small, so that the universe still has approximately the same composition.
Hans Albrecht Bethe was a German-American theoretical physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics, and solid-state physics, and who won the 1967 Nobel Prize in Physics for his work on the theory of stellar nucleosynthesis. For most of his career, Bethe was a professor at Cornell University.
The carbon-burning process or carbon fusion is a set of nuclear fusion reactions that take place in the cores of massive stars (at least 8 at birth) that combines carbon into other elements. It requires high temperatures (> 5×108 K or 50 keV) and densities (> 3×109 kg/m3).
The Cowan–Reines neutrino experiment was conducted by Washington University in St. Louis alumnus Clyde L. Cowan and Stevens Institute of Technology and New York University alumnus Frederick Reines in 1956. The experiment confirmed the existence of neutrinos. Neutrinos, subatomic particles with no electric charge and very small mass, had been conjectured to be an essential particle in beta decay processes in the 1930s. With neither mass nor charge, such particles appeared to be impossible to detect. The experiment exploited a huge flux of electron antineutrinos emanating from a nearby nuclear reactor and a detector consisting of large tanks of water. Neutrino interactions with the protons of the water were observed, verifying the existence and basic properties of this particle for the first time.
Stanford Earl Woosley is a physicist, and Professor of Astronomy and Astrophysics. He is the director of the Center for Supernova Research at University of California, Santa Cruz. He has published over 300 papers.
Nuclear astrophysics is an interdisciplinary part of both nuclear physics and astrophysics, involving close collaboration among researchers in various subfields of each of these fields. This includes, notably, nuclear reactions and their rates as they occur in cosmic environments, and modeling of astrophysical objects where these nuclear reactions may occur, but also considerations of cosmic evolution of isotopic and elemental composition (often called chemical evolution). Constraints from observations involve multiple messengers, all across the electromagnetic spectrum (nuclear gamma-rays, X-rays, optical, and radio/sub-mm astronomy), as well as isotopic measurements of solar-system materials such as meteorites and their stardust inclusions, cosmic rays, material deposits on Earth and Moon). Nuclear physics experiments address stability (i.e., lifetimes and masses) for atomic nuclei well beyond the regime of stable nuclides into the realm of radioactive/unstable nuclei, almost to the limits of bound nuclei (the drip lines), and under high density (up to neutron star matter) and high temperature (plasma temperatures up to 109 K). Theories and simulations are essential parts herein, as cosmic nuclear reaction environments cannot be realized, but at best partially approximated by experiments. In general terms, nuclear astrophysics aims to understand the origin of the chemical elements and isotopes, and the role of nuclear energy generation, in cosmic sources such as stars, supernovae, novae, and violent binary-star interactions.
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least eight times, but no more than 40 to 50 times, the mass of the Sun (M☉) to undergo this type of explosion. Type II supernovae are distinguished from other types of supernovae by the presence of hydrogen in their spectra. They are usually observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies; those are generally composed of older, low-mass stars, with few of the young, very massive stars necessary to cause a supernova.
Gerald Edward Brown was an American theoretical physicist who worked on nuclear physics and astrophysics. Since 1968 he had been a professor at the Stony Brook University. He was a distinguished professor emeritus of the C. N. Yang Institute for Theoretical Physics at Stony Brook University.
Friedrich-Karl "Friedel“ Thielemann is a German-Swiss theoretical astrophysicist.
p-nuclei (p stands for proton-rich) are certain proton-rich, naturally occurring isotopes of some elements between selenium and mercury inclusive which cannot be produced in either the s- or the r-process.
William David Arnett is a Regents Professor of Astrophysics at Steward Observatory, University of Arizona, known for his research on supernova explosions, the formation of neutron stars or black holes by gravitational collapse, and the synthesis of elements in stars; he is author of the monograph Supernovae and Nucleosynthesis which deals with these topics. Arnett pioneered the application of supercomputers to astrophysical problems, including neutrino radiation hydrodynamics, nuclear reaction networks, instabilities and explosions, supernova light curves, and turbulent convective flow in two and three dimensions.
James Michael Lattimer is a nuclear astrophysicist who works on the dense nuclear matter equation of state and neutron stars.
Vassiliki Kalogera is a Greek astrophysicist. She is a professor at Northwestern University and the Director of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She is a leading member of the LIGO Collaboration that observed gravitational waves in 2015.
Supernova neutrinos are weakly interactive elementary particles produced during a core-collapse supernova explosion. A massive star collapses at the end of its life, emitting on the order of 1058 neutrinos and antineutrinos in all lepton flavors. The luminosity of different neutrino and antineutrino species are roughly the same. They carry away about 99% of the gravitational energy of the dying star as a burst lasting tens of seconds. The typical supernova neutrino energies are 10–20 MeV. Supernovae are considered the strongest and most frequent source of cosmic neutrinos in the MeV energy range.
Christopher John Pethick is a British theoretical physicist, specializing in many-body theory, ultra-cold atomic gases, and the physics of neutron stars and stellar collapse.
Ken'ichi Nomoto is a Japanese astrophysicist and astronomer, known for his research on stellar evolution, supernovae, and the origin of heavy elements.
Madappa Prakash is an Indian-American nuclear physicist and astrophysicist, known for his research on the physics of neutron stars and heavy-ion collisions.
George Michael Fuller is an American theoretical physicist, known for his research on nuclear astrophysics involving weak interactions, neutrino flavor-mixing, and quark matter, as well as the hypothetical nuclear matter.
