GAMMA-RAYS
Gamma rays have the smallest wavelengths and the most energy of any wave in the electromagnetic spectrum, with photon energies greater than 100,000 eV.
They are produced by the hottest and
most energetic objects in the universe, such as neutron stars and pulsars, supernova explosions, and regions around black holes. On Earth, gamma waves are generated by nuclear explosions, lightning, and radioactive decay.
The most spectacular discovery in gamma-ray astronomy came in the late 1960's. Detectors on board military satellites began to record bursts of gamma-rays from deep space. Gamma-ray bursts are the brightest and most energetic electromagnetic events known to occur in the universe since the “Big Bang”. Bursts can last from ten milliseconds to several hours and can release more energy in 10 seconds than our Sun will emit in its entire expected 10-billion-year lifetime! In fact, they shine approximately a million trillion times brighter than the Sun. After an initial flash of gamma rays, a longer-lived "afterglow" is usually emitted at longer wavelengths (x-rays, ultraviolet, visible, infrared, microwave and radio waves).
Gamma-rays are ionizing radiation and are thus, like x-rays and some UV waves, biologically hazardous. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancer cells.