Related topics: black holes · gamma rays · neutron stars

Fermi mission reveals its highest-energy gamma-ray bursts

For 10 years, NASA's Fermi Gamma-ray Space Telescope has scanned the sky for gamma-ray bursts (GRBs), the universe's most luminous explosions. A new catalog of the highest-energy blasts provides scientists with fresh insights ...

Astronomers discover an unusual nuclear transient

An international group of astronomers has detected an unusual nuclear transient in the nucleus of a weakly active galaxy. The new transient was identified by the OGLE-IV Transient Detection System and received designation ...

High-speed supernova reveals earliest moments of a dying star

An international team of scientists, including astronomers from the Universities of Leicester, Bath and Warwick, have found evidence for the existence of a 'hot cocoon' of material enveloping a relativistic jet escaping a ...

The orderly chaos of black holes

During the formation of a black hole, a bright burst of very energetic light in the form of gamma rays is produced, these events are called gamma ray bursts. The physics behind this phenomenon includes many of the least understood ...

All in the family: Kin of gravitational wave source discovered

On October 16, 2017, an international group of astronomers and physicists excitedly reported the first simultaneous detection of light and gravitational waves from the same source—a merger of two neutron stars. Now, a team ...

VLA sky survey reveals first 'orphan' gamma ray burst

Astronomers comparing data from an ongoing major survey of the sky using the National Science Foundation's Karl G. Jansky Very Large Array (VLA) to data from earlier surveys likely have made the first discovery of the afterglow ...

Astronomers witness birth of new star from stellar explosion

The explosions of stars, known as supernovae, can be so bright they outshine their host galaxies. They take months or years to fade away, and sometimes, the gaseous remains of the explosion slam into hydrogen-rich gas and ...

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Gamma-ray burst

Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions in distant galaxies. They are the most luminous electromagnetic events occurring in the universe. Bursts can last from milliseconds to nearly an hour, although a typical burst lasts a few seconds. The initial burst is usually followed by a longer-lived "afterglow" emitting at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio).

Most observed GRBs are believed to be a narrow beam of intense radiation released during a supernova event, as a rapidly rotating, high-mass star collapses to form a black hole. A subclass of GRBs (the "short" bursts) appear to originate from a different process, possibly the merger of binary neutron stars.

The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime) and extremely rare (a few per galaxy per million years). All observed GRBs have originated from outside the Milky Way galaxy, although a related class of phenomena, soft gamma repeater flares, are associated with magnetars within the Milky Way. It has been hypothesized that a gamma-ray burst in the Milky Way could cause a mass extinction on Earth.

GRBs were first detected in 1967 by the Vela satellites, a series of satellites designed to detect covert nuclear weapons tests. Hundreds of theoretical models were proposed to explain these bursts in the years following their discovery, such as collisions between comets and neutron stars. Little information was available to verify these models until the 1997 detection of the first X-ray and optical afterglows and direct measurement of their redshifts using optical spectroscopy. These discoveries, and subsequent studies of the galaxies and supernovae associated with the bursts, clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies and connecting long GRBs with the deaths of massive stars.

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