Artist's illustration showing the life of a as converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a. Theoretically, energy may be released during the collapse along the axis of rotation to form a gamma-ray burst. In, gamma-ray bursts ( GRBs) are extremely energetic explosions that have been observed in distant. They are the brightest events known to occur in the.
Bursts can last from ten milliseconds to several hours. After an initial flash of, a longer-lived 'afterglow' is usually emitted at longer wavelengths (,,,, and ). The intense radiation of most observed GRBs is thought to be released during a or as a high-mass implodes to form a or a. A subclass of GRBs (the 'short' bursts) appear to originate from a (the merger of ). The cause of the precursor burst observed in some of these short events may be 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. The sources of most GRBs are billions of away from, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the 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, although a related class of phenomena, flares, are associated with within the Milky Way.
It has been hypothesized that a gamma-ray burst in the Milky Way, pointing directly towards the Earth, could cause a event. GRBs were first detected in 1967 by the, which had been designed to detect; this was declassified and published in 1973. Following their discovery, hundreds of theoretical models were proposed to explain these bursts, such as collisions between. 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 using optical, and thus their distances and energy outputs.
Dubrovački trombunjeri. 906 likes 156 talking about this. Dubrovački trombunjeri su povijesna vojna postrojba, po predaji utemeljena 1417. No gamma-ray burst from within our own galaxy, the Milky Way, has been observed, and the question of whether one has ever occurred remains unresolved. In light of evolving understanding of gamma-ray bursts and their progenitors, the scientific literature records a growing number of local, past, and future GRB candidates. Bondarenko zhelezobetonnie i kamennie konstrukcii.
These discoveries, and subsequent studies of the galaxies and associated with the bursts, clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies. Positions on the sky of all gamma-ray bursts detected during the BATSE mission. The distribution is, with no concentration towards the plane of the Milky Way, which runs horizontally through the center of the image. Gamma-ray bursts were first observed in the late 1960s by the U.S. Satellites, which were built to detect gamma radiation pulses emitted by nuclear weapons tested in space.
The suspected that the might attempt to conduct secret nuclear tests after signing the in 1963. On July 2, 1967, at 14:19, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons signature. Uncertain what had happened but not considering the matter particularly urgent, the team at the, led by, filed the data away for investigation.
As additional Vela satellites were launched with better instruments, the Los Alamos team continued to find inexplicable gamma-ray bursts in their data. By analyzing the different arrival times of the bursts as detected by different satellites, the team was able to determine rough estimates for the of sixteen bursts and definitively rule out a terrestrial or solar origin. The discovery was declassified and published in 1973. Most early theories of gamma-ray bursts posited nearby sources within the. From 1991, the (CGRO) and its Burst and Transient Source Explorer () instrument, an extremely sensitive gamma-ray detector, provided data that showed the distribution of GRBs is —not biased towards any particular direction in space. If the sources were from within our own galaxy they would be strongly concentrated in or near the galactic plane.