Description
Gamma-rays are the most energetic form of light and are produced by the hottest regions of the universe. They are also produced by such violent events as supernova explosions or the destruction of atoms, and by less dramatic events, such as the decay of radioactive material in space. Things like supernova explosions (the way massive stars die), neutron stars and pulsars, and black holes are all sources of celestial gamma-rays. A gamma ray is a packet of electromagnetic energy--a photon. Gamma photons are the most energetic photons in the electromagnetic spectrum. Gamma rays (gamma photons) are emitted from the nucleus of some unstable (radioactive) atoms. Gamma rays are an extremely high-energy form of electromagnetic (EM) radiation. Gamma ray radiation has a much, much shorter wavelength than visible light, so gamma ray photons have much, much higher energies than photons of light do. Gamma rays lie at the extreme high-energy end of the electromagnetic spectrum. X-rays, which have slightly lower energies than gamma rays, are the neighbors of gamma rays along the EM spectrum. In fact, the spectral ranges of hard X-rays and gamma rays overlap. Gamma rays have wavelengths of about 100 picometers (100 x 10-12 meters) or shorter, or energies per photon of at least around 10 keV. This type of electromagnetic wave oscillates with a frequency of 3 exahertz (EHz or 1018 hertz) or higher. There is no sharp distinction between the highest energy X-rays and the lowest energy gamma rays. The distinction between X-rays and gamma rays is actually based on the origin of the radiation, not on the frequency or wavelength of the electromagnetic waves. Gamma rays are produced by nuclear transitions, while X-rays are the result of accelerating electrons. Photons with energies between about 10 keV and a few hundred keV can be either hard X-rays or gamma rays. These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells. Gamma-rays travel to us across vast distances of the universe, only to be absorbed by the Earth's atmosphere. Different wavelengths of light penetrate the Earth's atmosphere to different depths. NASA Swift observatory mission Video Swift is a multi-wavelength observatory dedicated to the study of gamma-ray burst science. Its 3 instruments work together to observe GRBs and afterglows in the gamma-ray, ultraviolet and optical wavebands. Gamma-ray bursts A Gamma-ray burst could wipe out all living species on the planet Earth at any time with no warning and destroy the ozone layer in the process. There is no protection for the planet from this fate. Gamma-ray bursts (GRBs) pose one of the greatest mysteries of modern astronomy. About once a day, the sky lights up with a spectacular flash, or burst, of gamma-rays. More often than not, this burst out shines all of the other sources of cosmic gamma-rays added together. The source of the burst then disappears altogether. No one can predict when the next burst will occur or from what direction in the sky it will come.