The cosmic microwave background, or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost uniform and is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the electromagnetic spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s.
In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic events occurring in distant galaxies which represent the brightest and "most powerful class of explosions [sic] in the universe." These extreme electromagnetic events are second only to the Big Bang as the most energetic and luminous phenomenon ever known. Gamma-ray bursts can last from ten milliseconds to several hours. After the initial flash of gamma rays, a longer-lived § Afterglow is emitted, usually in the longer wavelengths of X-ray, ultraviolet, optical, infrared, microwave or radio frequencies.
A blazar is an active galactic nucleus (AGN) with a relativistic jet directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away from Earth. Blazars are powerful sources of emission across the electromagnetic spectrum and are observed to be sources of high-energy gamma ray photons. Blazars are highly variable sources, often undergoing rapid and dramatic fluctuations in brightness on short timescales. Some blazar jets appear to exhibit superluminal motion, another consequence of material in the jet traveling toward the observer at nearly the speed of light.
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray with an energy greater than 1 EeV (1018 electronvolts, approximately 0.16 joules), far beyond both the rest mass and energies typical of other cosmic ray particles. The origin of these highest energy cosmic ray is not known.
David Norman Schramm was an American astrophysicist and educator, and one of the world's foremost experts on the Big Bang theory. Schramm was a pioneer in establishing particle astrophysics as a vibrant research field. He was particularly well known for the study of Big Bang nucleosynthesis and its use as a probe of dark matter and of neutrinos. He also made important contributions to the study of cosmic rays, supernova explosions, heavy-element nucleosynthesis, and nuclear astrophysics generally.
The Extreme Universe Space Observatory onboard Japanese Experiment Module (JEM-EUSO) is the first space mission concept devoted to the investigation of cosmic rays and neutrinos of extreme energy (E > 5×1019 eV). Using the Earth's atmosphere as a giant detector, the detection is performed by looking at the streak of fluorescence produced when such a particle interacts with the Earth's atmosphere.
VERITAS is a major ground-based gamma-ray observatory with an array of four 12 meter optical reflectors for gamma-ray astronomy in the GeV – TeV photon energy range. VERITAS uses the Imaging Atmospheric Cherenkov Telescope technique to observe gamma rays that cause particle showers in Earth's atmosphere that are known as extensive air showers. The VERITAS array is located at the Fred Lawrence Whipple Observatory, in southern Arizona, United States. The VERITAS reflector design is similar to the earlier Whipple 10-meter gamma-ray telescope, located at the same site, but is larger in size and has a longer focal length for better control of optical aberrations. VERITAS consists of an array of imaging telescopes deployed to view atmospheric Cherenkov showers from multiple locations to give the highest sensitivity in the 100 GeV – 10 TeV band. This very high energy observatory, completed in 2007, effectively complements the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope due to its larger collection area as well as coverage in a higher energy band.
Astroparticle physics, also called particle astrophysics, is a branch of particle physics that studies elementary particles of astrophysical origin and their relation to astrophysics and cosmology. It is a relatively new field of research emerging at the intersection of particle physics, astronomy, astrophysics, detector physics, relativity, solid state physics, and cosmology. Partly motivated by the discovery of neutrino oscillation, the field has undergone rapid development, both theoretically and experimentally, since the early 2000s.
Extragalactic cosmic rays are very-high-energy particles that flow into the Solar System from beyond the Milky Way galaxy. While at low energies, the majority of cosmic rays originate within the Galaxy (such as from supernova remnants), at high energies the cosmic ray spectrum is dominated by these extragalactic cosmic rays. The exact energy at which the transition from galactic to extragalactic cosmic rays occurs is not clear, but it is in the range 1017 to 1018 eV.
The Yuan-Tseh Lee Array for Microwave Background Anisotropy, also known as the Array for Microwave Background Anisotropy (AMiBA), is a radio telescope designed to observe the cosmic microwave background and the Sunyaev-Zel'dovich effect in clusters of galaxies.
Gamma-ray astronomy is a subfield of astronomy where scientists observe and study celestial objects and phenomena in outer space which emit cosmic electromagnetic radiation in the form of gamma rays, i.e. photons with the highest energies at the very shortest wavelengths. Radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy.
Uroš Seljak is a Slovenian cosmologist and a professor of astronomy and physics at University of California, Berkeley. He is particularly well-known for his research in cosmology and approximate Bayesian statistical methods.
Wendy Laurel Freedman is a Canadian-American astronomer, best known for her measurement of the Hubble constant, and as director of the Carnegie Observatories in Pasadena, California, and Las Campanas, Chile. She is now the John & Marion Sullivan University Professor of Astronomy and Astrophysics at the University of Chicago. Her principal research interests are in observational cosmology, focusing on measuring both the current and past expansion rates of the universe, and on characterizing the nature of dark energy.
Hakkı Boran Ögelman was a Turkish physicist and astrophysicist. He was an expert on gamma ray astronomy, the physics of neutron stars, and solar energy and worked on several key topics in modern astrophysics. He made many contributions to high energy astrophysics. In his early professional career he engaged in the SAS-II Small Gamma Ray Astronomy Satellite experiment development, data analysis, and first detection and imaging of our universe in gamma rays with his NASA colleagues, as well as in other fields of physics. His main interests in the field of astrophysics were the study of gamma ray astronomy and compact objects such as neutron stars and pulsars. Ögelman worked at NASA Goddard Space Flight Center, Middle East Technical University (METU) in Ankara, Turkey, Çukurova University in Adana, Turkey, Max Planck Institute (MPI) at Garching, Germany and the University of Wisconsin.
Multi-messenger astronomy is the coordinated observation and interpretation of multiple signals received from the same astronomical event. Many types of cosmological events involve complex interactions between a variety of astrophysical processes, each of which may independently emit signals of a characteristic "messenger" type: electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays. When received on Earth, identifying that disparate observations were generated by the same source can allow for improved reconstruction or a better understanding of the event, and reveals more information about the source.
Peter M. Garnavich is a faculty member of the Department of Physics and Astronomy at the University of Notre Dame. His primary research area is the study of supernovae and their diversity. He has also studied gamma ray bursts and cataclysmic variable stars. Garnavich is a member of a supernova search team that contributed to the discovery of dark energy in 1998. At Notre Dame, Garnavich has developed and participated in collaborations using the Spitzer Space Telescope, the Large Binocular Telescope, the Hubble Space Telescope, and the Kepler Space Telescope. He was named a fellow of the American Astronomical Society (AAS) in 2024.
Erika Tobiason Hamden is an American astrophysicist and associate professor at the University of Arizona and Steward Observatory. Her research focuses on developing ultraviolet (UV) detector technology, ultraviolet–visible spectroscopy (UV/VIS) instrumentation and spectroscopy, and galaxy evolution. She served as the project scientist and project manager of a UV multi-object spectrograph, FIREBall-2, that is designed to observe the circumgalactic medium (CGM). She is a 2019 TED fellow.
Alexey Vikhlinin is a Russian-American astrophysicist notable for achievements in the astrophysics of high energy phenomenon, namely galaxy cluster cosmology and the design of space-based X-ray observatories. He is currently a senior astrophysicist at the Smithsonian Astrophysical Observatory, part of the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts. He was recently the Science and Technology Definition Team (STDT) Community Co-chair for the Lynx X-ray Observatory, a NASA-funded Large Mission Concept Study under consideration by the 2020 Decadal Survey on Astronomy and Astrophysics.
Abigail Goodhue Vieregg is a professor of physics at the Enrico Fermi Institute and Kavli Institute of Cosmology, University of Chicago, specializing in neutrino astrophysics and cosmology. Her work focuses on cosmic high-energy neutrinos and mapping the cosmic microwave background.
Elisa Resconi is an Italian astroparticle physicist and the Chair of Experimental Physics with Cosmic Particles at the Technical University of Munich, Germany. Her research concentrates on high-energy neutrino astronomy and developing advanced detection technologies for cosmic particles.
