Brighter colors in the Cygus region indicate greater numbers of gamma rays detected by the Fermi gamma-ray space telescope. Krause et al. Electromagnetic Spectrum Series Series Homepage. Infrared Waves. Reflected Near-Infrared. Visible Light. Ultraviolet Waves. Earth's Radiation Budget. Diagram of the Electromagnetic Spectrum. Recommended Articles. September 24, Solar Eclipse - June 10, June 09, Aurora-Chasing Citizen Scientists Help November 13, Episode 21 - Our Next Solar Cycle.
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. Instruments aboard high-altitude balloons and satellites like the Compton Observatory provide our only view of the gamma-ray sky.
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.
How do we "see" using gamma-ray light? Gamma-ray astronomy did not develop until it was possible to get our detectors above all or most of the atmosphere, using balloons or spacecraft. The first gamma-ray telescope, carried into orbit on the Explorer XI satellite in , picked up fewer than cosmic gamma-ray photons!
Unlike optical light and X-rays, gamma rays cannot be captured and reflected in mirrors. Gamma decay occurs when there is too much energy in the nucleus of an atom, causing it to emit a gamma ray without changing its charge or mass composition. Gamma rays are sometimes used to treat cancerous tumors in the body by damaging the DNA of the tumor cells. However, great care must be taken, because gamma-rays can also damage the DNA of surrounding healthy tissue cells.
One way to maximize the dosage to cancer cells while minimizing the exposure to healthy tissues is to direct multiple gamma-ray beams from a linear accelerator, or linac, onto the target region from many different directions.
This is the operating principle of CyberKnife and Gamma Knife therapies. Gamma Knife radiosurgery uses specialized equipment to focus close to tiny beams of radiation on a tumor or other target in the brain. Each individual beam has very little effect on the brain tissue it passes through, but a strong dose of radiation is delivered at the point where the beams meet, according to Mayo Clinic. One of the more interesting sources of gamma rays are gamma-ray bursts GRBs.
These are extremely high-energy events that last from a few milliseconds to several minutes. They were first observed in the s, and they are now observed somewhere in the sky about once a day. Gamma-ray bursts are "the most energetic form of light," according to NASA. They shine hundreds of times brighter than a typical supernova and about a million-trillion times as bright as the sun.
According to Robert Patterson, a professor of astronomy at Missouri State University, GRBs were once thought to come from the last stages of evaporating mini black holes. They are now believed to originate in collisions of compact objects such as neutron stars. Other theories attribute these events to the collapse of supermassive stars to form black holes.
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