Gamma-ray burst

Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe. Bursts can last from ten milliseconds to several hours. The initial burst is usually followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio).

Most observed GRBs are believed to consist of a narrow beam of intense radiation released during a supernova or hypernova as a rapidly rotating, high-mass star collapses to form a neutron star, quark star, or black hole. A subclass of GRBs (the "short" bursts) appear to originate from a different process: the merger of binary neutron stars. The cause of the precursor burst observed in some of these short events may be due to the development of a resonance between the crust and core of such stars as a result of the massive tidal forces experienced in the seconds leading up to their collision, causing the entire crust of the star to shatter.

GRB 970508

GRB 970508 was a gamma-ray burst (GRB) detected on May 8, 1997, at 21:42 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived "afterglow" emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, and radio).

GRB 970508 was detected by the Gamma Ray Burst Monitor on the Italian–Dutch X-ray astronomy satellite BeppoSAX. Astronomer Mark Metzger determined that GRB 970508 occurred at least 6 billion light years from Earth; this was the first measurement of the distance to a gamma-ray burst.

Until this burst, astronomers had not reached a consensus regarding how far away GRBs occur from Earth. Some supported the idea that GRBs occur within the Milky Way, but are visibly faint because they are not highly energetic. Others concluded that GRBs occur in other galaxies at cosmological distances and are extremely energetic. Although the possibility of multiple types of GRBs meant that the two theories were not mutually exclusive, the distance measurement unequivocally placed the source of the GRB outside the Milky Way, effectively ending the debate.

Gamma ray

Gamma radiation (sometimes called gamma ray), denoted by the lower-case Greek letter gamma (γ), is extremely high-frequency electromagnetic radiation and therefore consists of high-energy photons. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays. Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays.

Gamma rays are ionizing radiation, and are thus biologically hazardous. Decay of an atomic nucleus from a high energy state to a lower energy state, a process called gamma decay, produces gamma radiation. This is what Villard had observed.

Natural sources of gamma rays on Earth include gamma decay of radionuclides and secondary radiation from atmospheric interactions with cosmic ray particles. Rare terrestrial natural sources produce gamma rays that are not of a nuclear origin, such as lightning strikes and terrestrial gamma-ray flashes. Additionally, gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced, that in turn cause secondary gamma rays via bremsstrahlung, inverse Compton scattering, and synchrotron radiation. However, a large fraction of such astronomical gamma rays are screened by Earth's atmosphere and can only be detected by spacecraft. Gamma rays are produced by nuclear fusion in stars including the Sun (such as the CNO cycle), but are absorbed or inelastically scattered by the stellar material before escaping and are not observable from Earth.

Gamma ray (disambiguation)

Gamma rays are a form of electromagnetic radiation.

Gamma Ray may also refer to:

Gamma Ray (band)

Gamma Ray is a power metal band from Hamburg, northern Germany, founded and fronted by Kai Hansen after his departure from the German power metal band Helloween. Hansen is the current lead vocalist, guitarist as well as the chief songwriter of Gamma Ray. The band is known as one of the most prominent bands of the German heavy metal scene.

Biography

Formation

In 1988, after four years with the German power metal band Helloween, guitarist and songwriter Kai Hansen decided, for reasons that are still the subject of much debate, to leave the group. Hansen claimed that Helloween had become too big for him to handle, although the group's troubles with financial issues and their record company, Noise Records, most likely played a part as well. He proceeded to do some studio work with German power metal band Blind Guardian and in 1989 decided to form his own project with long-time friend Ralf Scheepers, former vocalist of the band Tyran Pace. This two-man project grew into a four-man band with the addition of Uwe Wessel on bass and Mathias Burchardt on drums. This was the first line-up of Gamma Ray, bearing a sound understandably close to that of Helloween of that period.