Photons of light are massless particles that are essentially packets of energy., Due to a quantum mechanical phenomenon known as wave–particle duality, particles can behave like waves and photons are no different.
photons have wavelength, and the amplitude of their wavelength determines where they lie on the electromagnetic spectrum. Radio and microwave photons are found at the low-energy, long-wavelength end of the spectrum, while ultraviolet, X-ray, and more photons are found in the high-energy, short-wavelength regime. The energy source of them all is the shortest wavelength: gamma rays.
Gamma rays have a wavelength less than 10^-11 meters and a frequency greater than 30 x 10^18 Hz., The European Space Agency describes how gamma-ray photons have energies greater than 100,000 electron volts (eV). We can compare this to X-rays, which NASA describes as having energies between 100 eV and 100,000 eV, and optical photons that we can see with our eyes, which are about 1 eV.
At the beginning of the 20th century, two forms of radiation emitted by decaying atoms were known, namely alpha particles (which are helium nuclei) and beta particles (which are electrons and positrons).
Blocking gamma rays requires a denser material, and the thickness of that material depends on the material. It takes 4.2 cubic meters of water, 2 meters of concrete or 0.39 meters of lead to reduce the power of incoming gamma rays by one billionth.
This is a problem for gamma-ray telescopes such as NASA’s Fermi Space Telescope., Ordinary telescopes, such as the Hubble Space Telescope, use mirrors and lenses to collect and focus light, but gamma rays pass straight through ordinary telescopes. Instead, gamma-ray telescopes have to employ other means.
In it fermi space telescope, a gamma-ray photon will pass through a device called an anti-coincidence detector, which blocks out errant cosmic rays. The gamma ray is then absorbed by one of 16 sheets of tungsten, a material dense enough to block gamma rays.
Interacting with tungsten, the gamma ray is converted into an electron and a positron (the antimatter or antimatter counterpart of an electron), whose paths are read by a tracker, which is a series of silicon strips woven together by tungsten foil. is module. Which, based on the path of electrons and positrons, can determine the direction of gamma rays that are coming from space.
Finally, the energy of the electron and then the positron is measured with a calorimeter, a device that measures the energy of a particle when it is absorbed, made of cesium iodide and so the energy of the gamma rays can be determined.
Because of their high energy, gamma rays are ionizing, meaning they can knock electrons out of atoms, eventually damaging living cells and posing a health hazard. However, as with all radiation, it depends on the dose you receive.
Given their ionizing power, it is fortunate that Earth’s atmosphere can block gamma rays from space. For astronomers, however, this is unfortunate, as it means that in order to accomplish gamma-ray astronomy, observatories must be built on mountains where the atmosphere is thinnest or sent into space.
reference:
- Cambridge University 2022. Flash! Biggest Explosion in the Universe Discovered by Sarkar Schilling (press release)
