A hypernova is a very energetic supernova which is believed to result from an extreme core collapse scenario. In this case, a massive star (>30 solar masses) collapses to form a rotating black hole emitting twin astrophysical jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release such intense gamma rays that they often appear similar to a type Ic supernova, but with unusually broad spectral lines indicating an extremely high expansion velocity. Hypernovae are one of the mechanisms for producing long gamma ray bursts (GRBs), which range from 2 seconds to over a minute in duration. They have also been referred to as superluminous supernovae, though that classification also includes other types of extremely luminous stellar explosions that have different origins.
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Hypernova in the context of Gamma-ray astronomy
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 (above 100 keV) at the very shortest wavelengths. X-ray astronomy uses the next lower energy range, X-ray radiation, with energy below 100 keV.
In most cases, gamma rays from solar flares and Earth's atmosphere fall in the MeV range, but it's now known that solar flares can also produce gamma rays in the GeV range, contrary to previous beliefs. Much of the detected gamma radiation stems from collisions between hydrogen gas and cosmic rays within our galaxy. These gamma rays, originating from diverse mechanisms such as electron-positron annihilation, the inverse Compton effect and in some cases gamma decay, occur in regions of extreme temperature, density, and magnetic fields, reflecting violent astrophysical processes like the decay of neutral pions. They provide insights into extreme events like supernovae, hypernovae, and the behavior of matter in environments such as pulsars and blazars. A huge number of gamma ray emitting high-energy systems like black holes, stellar coronas, neutron stars, white dwarf stars, remnants of supernova, clusters of galaxies, including the Crab Nebula and the Vela Pulsar (the most powerful source so far), have been identified, alongside an overall diffuse gamma-ray background along the plane of the Milky Way galaxy. Cosmic radiation with the highest energy triggers electron-photon cascades in the atmosphere, while lower-energy gamma rays are only detectable above it. Gamma-ray bursts, like GRB 190114C, are transient phenomena challenging our understanding of high-energy astrophysical processes, ranging from microseconds to several hundred seconds.
Hypernova in the context of SN 2006gy
SN 2006gy was an extremely energetic supernova, also referred to as a hypernova, that was discovered on September 18, 2006. It was first observed by Robert Quimby and P. Mondol, and then studied by several teams of astronomers using facilities that included the Chandra, Lick, and Keck Observatories. In May 2007, NASA and several of the astronomers announced the first detailed analyses of the supernova, describing it as the "brightest stellar explosion ever recorded". In October 2007, Quimby announced that SN 2005ap had broken SN 2006gy's record as the brightest-ever recorded supernova, and several subsequent discoveries are brighter still. Time magazine listed the discovery of SN 2006gy as third in its Top 10 Scientific Discoveries for 2007.
Hypernova in the context of Stellar explosion
Stellar explosion can refer to:
- Nova
- Kilonova
- Micronova
- Supernova
- Supernova impostor, stellar explosions that appear similar to supernova, but do not destroy their progenitor stars
- Luminous red nova, an explosion thought to be caused by stellar collision
- Solar flares are a minor type of stellar explosion
- Tidal disruption event, the pulling apart of a star by tidal forces