Gamma rays are high-energy photons produced by some of the most violent events in the universe.
Photons of light are massless particles that are essentially packets of energy. a quantum-mechanical phenomenon known as wave-particle dualityParticles can behave like waves, and photons are no different. Photons have wavelengths, and the amplitude of their wavelength determines where they sit on electromagnetic spectrum, Radio and microwave photons sit at the low-energy, long-wavelength end of the spectrum, while in the short-wavelength, high-energy regime are the photons of the ultraviolet, X-rays, and the most energetic of those with the shortest wavelength: gamma rays. Rays.
Gamma rays have a wavelength less than 10^11 meters and a frequency greater than 30 x 10^18 Hz. European Space Agency explains how gamma-ray photons are Energy over 100,000 electron volts (opens in new tab) (EV). We can compare this to X-rays, which NASA describes as energy between 100 eV and 100,000 eV (opens in new tab)and optical photons that we can see with our eyes, which are around 1 eV.
related: What is Cosmic Microwave Background?
On Earth, gamma rays are produced by radioactive decay, nuclear weapons, and lightning, whereas in space They come from violent, high-energy sources such as solar flares, Kaiser, black holes breaking starsblack-hole accretion disk, exploding stars and the strong gravitational environment of neutron stars,
How were gamma rays discovered?
At the turn of the 20th century, two forms of radiation emitted by decaying atoms ie were known alpha particle (which are helium nuclei) and beta particles (which are electrons and positron).
However, when the French chemist Paul Willard began experimenting with the radioactive element radium, which had been discovered two years before Marie and Pierre CurieHe observed that the ionizing radiation resulting from the decay of radium packs a harder punch than alpha or beta particles.
This radiation got its name – gamma-rays – only because gamma is the third letter in the Greek alphabet after alpha and beta. Willard and his colleagues in the early 1900s did not know that the main difference between gamma rays and alpha/beta particles is that gamma rays are a form of light, while alpha and beta particles are made of matter.
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how to block gamma rays
Blocking gamma rays requires a denser material, and the thickness of that material depends on the material. According to Radiation Protection Solutions, to reduce the power of incoming gamma rays by one billion, you need 13.8 feet (4.2 m) of water, 6.6 feet (2 m) of concrete or 1.3 feet (0.39 m) of lead. Website Stemrad,
This is a problem for gamma-ray telescopes like NASA’s fermi space telescope, simple binoculars Hubble Space Telescope Use mirrors and lenses to collect and focus light, but gamma rays will pass straight through ordinary telescopes. Instead, gamma-ray telescopes have to employ other means.
On the Fermi Space Telescope, a gamma-ray photon will pass through a device called an anti-coercion detector, which blocks cosmic rays This can give false signals, according to nasa , The gamma-rays are then absorbed by one of 16 sheets of tungsten, a material dense enough to block gamma rays.
By interacting with tungsten, the gamma-ray is converted into an electron and a positron (the antimatter or antiparticle equivalent of the electron), the paths of which are read by a tracker, which is a module of silicon strips held by tungsten foil. Which can determine the direction of gamma-rays in space based on the trajectories of electrons and positrons.
Finally, the energy of the electron and then the positron is measured by a calorimeter—a device that measures the energy of a particle by absorbing it—made of cesium iodide, and so the energy of the gamma-ray can be determined. .
Are gamma rays dangerous?
Because of their high energy, gamma rays are ionizing, meaning they can strip electrons. atoms, eventually harm living cells and pose a health hazard. However, like all radiation, it depends on the dose you receive.
In small doses, very carefully targeted to limit exposure, they can be used safely as medical diagnostic tools, or even to kill cancer cells ( Ironically, exposure to radiation, including gamma rays, can cause cancer). In particular, is a device used by doctors’gamma knife‘, which is an ultra-precise form of surgery in which a beam of gamma rays cuts away diseased cells of the brain and can even penetrate deep into the brain without damaging the outer lobe.
gamma-ray astronomy
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Given their ionizing power, it is fortunate Earth’s atmosphere Capable of intercepting gamma rays from space. However, for astronomers, this is unfortunate, as it means conducting gamma-ray astronomy Observatories should either be built on mountain tops where the atmosphere is thin or sent into space.
The first Gamma-ray Space Telescope was launched on NASA in 1961 explorer 11 satellites, but things didn’t really start with a major discovery until the late 1960s and early 1970s, and it wasn’t even an astronomical telescope that made the discovery.
Over the years a number of observatories, both on the ground and in space, have been designed to observe cosmic gamma-ray radiations. In 1990, NASA launched Compton Gamma-Ray Observatory As a gamma-ray counterpart to the Hubble Space Telescope. The Compton Gamma-ray Observatory explored the universe from 1991 to 2000. Above beposax was a joint Italian-Dutch mission that operated between 1996 and 2003, while NASA launched HETE-2 (High-Energy Transient Explorer; HETE-1 had previously failed in orbit) which tracked several GRBs between 2000 and 2008.
Currently, by the end of 2022, many satellitesGamma-ray astronomy continues to be conducted at both observatories and telescopes. Earth And in space. NASA’s Swift SatelliteLaunched in 2004, combines both X-ray and gamma-ray observations, as does Italy’s agile The satellite was launched in 2007. In 2002, the European Space Agency launched integralinternational gamma-ray astrophysics The laboratory.. Currently the most sophisticated gamma-ray space telescope is Fermi, which was launched by NASA in 2008.
Meanwhile, there are several gamma-ray observatories on the ground including Veritas at the Fred Lawrence Whipple Observatory in Arizona (Very Energetic Radiation Imaging Telescope Array System) and Hayes (High Energy Stereoscopic System) in Namibia.
gamma ray bursts
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In 1963, the Soviet Union, the United Kingdom and the United States signed a Nuclear Test Ban Treaty, which prohibited the world’s superpowers from testing any nuclear devices in the atmosphere or in space. However, the US suspected that the Soviet Union would not abide by the treaty, so they launched the Vela series of satellites to look for any pulses of gamma-ray radiation coming from clandestine nuclear explosions. As it happened, gamma rays were detected, but from space: random bursts of powerful gamma-ray energy that seemed to be coming from all around Earth. but how far were they gamma-ray bursts,
related: Most powerful gamma-ray burst ever observed may shed light on how black holes are born
If these gamma-ray bursts, which are abbreviated as GRBs, were coming from our galaxy, astronomers would have found them mostly in the plane of the planet. Galaxy, Instead, they were spread across the sky, which can only mean one of two things. either they were very close, within us The Solar System, or they were far away, beyond our galaxy. A special debate was also convened in 1995, echoing something similar.great debate‘ between Harlow Shapley and Heber D. Curtis in 1920, which discussed the size of our galaxy based on the distribution round flakes,
in 1995 debateHeaded by Martin Reiss, astronomer Bohdan Paczynski of Princeton University argued that GRBs came from very far away, while Donald Lamb of the University of Chicago argued that GRBs must be from nearby because the energy required for them must be billions of light-years. Distant would violate the laws of physics.
Just two years later astronomers had their answer when the BeppoSAX satellite detected a gamma-ray burst that William Herschel Telescope The process was able to quickly follow-up the slow light detection of any GRBs forming in the Canary Islands. is measuring red shift subsequent flashes showed that it came from six billion light years far. Bohdan Paczynski was right!
There are two main types of GRBs. One type is called a short GRB which lasts only fractions of a second, while the other type is known as a long GRB, and can last for several seconds up to an hour. short GRBS are emitted during the merger of two neutron starsWhile long GRBs are the death knell of the rare, massive stars,
Physicists Andrew McFadden and Stan Woosley of the University of California, Santa Cruz, developed a model To explain how stars can explode and generate long GRBs without breaking the laws of physics. When a massive star with 50-100 times the mass sun reaches the end of his life, Star begins to collapse at its center, and if the star is spinning fast enough, the energy within the collapsing layers is ejected from the core and dissipated in two jets that move approximately speed of light And separate the star. Charged particles within these jets spiral around the powerful magnetic field and produce something called synchrotron radiation, which we see in the form of gamma rays. Because the gamma rays are released only in the direction of the jets, and not in all directions at once, the total energy released does not violate the laws of physics.
additional resources
Learn more about ionizing radiation with United States Environmental Protection Agency (EPA), And this American Cancer Society, Explore gamma rays in greater detail across the electromagnetic spectrum NASA Science.
Follow Keith Cooper on Twitter @21stCenturySETI. follow us on twitter @Spacedotcom and on Facebook,
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Flash! The Hunt for the Biggest Explosion in the Universe by Government Shilling (Cambridge University Press, 2002)
The Biggest Bangs: The Mystery of Gamma-Ray Bursts, the Most Violent Explosions in the Universe by Jonathan Katz (Oxford University Press, 2002)