Gamma ray

A gamma ray, also known as gamma radiation (symbol γ), is a type of electromagnetic radiation. Gamma rays carry more energy and have a shorter wavelength than any other kind of electromagnetic wave in the electromagnetic spectrum.[1][2]

Gamma rays penetrate (pass through) matter much more easily than other forms of radiation.[3] In fact, gamma rays are even more penetrating than X-rays.[4] This makes them both useful and dangerous. Gamma rays are carefully used to treat certain cancers or other health conditions. They also have a role in food safety and studying outer space.

Many things can produce gamma rays, including the hottest and highest-energy objects in the universe.[1] On Earth, gamma rays can also come from lightning[2], nuclear explosions, and the the radioactive decay of atomic nuclei.[1]

Discovery

Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium.[2]

By 1900, physicist Ernest Rutherford coined the term "gamma rays". "Gamma" is the third letter of the Greek alphabet. Rutherford identified three types of radiation that are produced by radioactive decay. He named the three types alpha, beta, and gamma radiation. He put them in order from least to most penetrating power. Because gamma rays can pass through matter much more easily than the other forms of radiation, he listed it third.

In 1903, Ernest Rutherford named this radiation "gamma rays" because they were the third type of radiation he discovered (after alpha and beta rays). ("Gamma" is the third letter of the Greek alphabet.) He they strongly penetrated matter.

By 1900, Rutherford had already named two less penetrating types of decay radiation (discovered by Henri Becquerel): alpha rays and beta rays (in the order of penetrating power). Gamma rays pass through matter much more easily than alpha or beta rays do.

Origin

According to NASA, these things can produce gamma rays:[1]

Danger

Gamma rays are ionizing radiation and are hazardous to life. They can damage bone marrow and internal organs.

Unlike alpha and beta rays, gamma rays easily pass through the body (and other objects). This makes it difficult to protect people from this type of radiation. Shielding made from lead or concrete is required.

On Earth, the magnetosphere protects life from most types of lethal cosmic radiation - but not gamma rays.

Uses

Food safety

Gamma radiation is often used to kill living things, in a process called irradiation. For example, irradiation is used to remove decay-causing bacteria from many foods, and to prevent fruits and vegetables from sprouting in order to maintain their freshness or flavor.

Treating cancer

Even though gamma rays can cause cancer, they also kill cancer cells. For this reason, gamma rays are used to treat some types of cancer.

A procedure called gamma-knife radiosurgery can be used to kill cancer cells. This is not an actual surgery. The procedure is

Instead, the procedure directs highly focused beams of gamma rays towards a tumor in the brain or upper spine.[5] This concentrates the radiation on the tumor while also minimizing damage to the body tissues around it.

This is especially helpful if a tumor is in a location that doctors can't reach using traditional surgery.[5] Gamma-knife surgery can also be used alongside traditional surgery to prevent a tumor from growing.[5]

Treating other health conditions

Gamma-knife surgery is also used to treat other health conditions. These include arteriovenous malformation (AVM), epilepsy, tremors, and trigeminal neuralgia (a chronic nerve disorder which causes sudden severe pain in the face[6]).[5]

Nuclear medicine uses gamma rays in imaging techniques (like PET scans) in order to diagnose problems.[7] They can also be used to sterilize medical equipment.[8]

Non-medical science

According to NASA, gamma rays can also be used to determine what elements exist on other planets.[1]

NASA also writes:[1]

Gamma-ray bursts [in outer space] are the most energetic and [brightest] electromagnetic events since the Big Bang and can release more energy in 10 seconds than our Sun will emit in its entire 10-billion-year expected lifetime! Gamma-ray astronomy presents unique opportunities to explore these exotic objects. By exploring the universe at these high energies, scientists can search for new physics, testing theories and performing experiments that are not possible in Earth-bound laboratories.

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 "Gamma Rays - NASA Science". 2016-08-10. Retrieved 2025-09-17.
  2. ↑ 2.0 2.1 2.2 "Via NASA Plane, Scientists Find New Gamma-ray Emission in Storm Clouds - NASA Science". 2024-10-02. Retrieved 2025-09-17.
  3. ↑ "Gamma ray | Definition, Uses, Wavelength, Production, Examples, & Facts | Britannica". www.britannica.com. 2025-08-23. Retrieved 2025-09-17.
  4. ↑ "Atom - Radioactivity, Particles, Discovery | Britannica". www.britannica.com. 2025-09-07. Retrieved 2025-09-17.
  5. ↑ 5.0 5.1 5.2 5.3 "What Is Gamma Knife Surgery?". Cleveland Clinic. Retrieved 2025-09-17.
  6. ↑ "Trigeminal neuralgia - Symptoms and causes". Mayo Clinic. Retrieved 2025-09-17.
  7. ↑ "Positron Emission Tomography (PET)". Johns Hopkins Medicine. Retrieved 2025-09-17.
  8. ↑ Harrell, C. Randall; Djonov, Valentin; Fellabaum, Crissy; Volarevic, Vladislav (2018). "Risks of Using Sterilization by Gamma Radiation: The Other Side of the Coin". International Journal of Medical Sciences. 15 (3): 274–279. doi:10.7150/ijms.22644. ISSN 1449-1907. PMC 5820857. PMID 29483819.
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