What are Gamma Rays? Everything You Need to Know

x-rays vs gamma rays

What are Gamma Rays? Everything You Need to Know

You’ve probably seen what gamma rays did to Bruce Banner, transforming him into the Incredible Hulk. No worries, this won’t happen to you; while this form of radiation can certainly alter the composition of skin cells, you don’t have to worry about your skin turning green.

As the most powerful form of light energy, gamma rays can pierce through just about any material. While it has the potential to harm, we’re learning more about how to harness its potential. Keep reading for everything you should know about gamma rays.

Gamma Rays: A Complete Explanation

Gamma rays are radiation that makes up a portion of the electromagnetic spectrum, which contains the entire range of energy waves. Gamma rays are the final section of the spectrum, featuring the shortest wavelengths and highest power among the types of radiation. This energy measures just the size of a nucleus at its larger section.

While studying the EM spectrum, scientists primarily use frequency (Hertz), wavelength (meters), or energy (electron volts), depending on which metric is easier to work with. As radiation gets quicker, researchers tend to use electron volts. In this regard, gamma rays are typically anything more than 200keV.

Gamma rays were one of the last portions of the electromagnetic spectrum to be discovered. They occur naturally on Earth as radioactive decay and in space as large bouts of nuclear fusion. Scientists also study them in labs using nuclear fission.

Due to their incredibly high energy level, gamma rays have the unique ability to travel through many objects, including the human body. As a result, they have the potential to cause significant harm to people when exposed in concentrated amounts. To study their characteristics, scientists use dense lead to create shields that can withstand it.

Despite the hazards, the ability for gamma rays to pass through objects makes them ideal in several applications. Some uses for this type of radiation include cancer treatment, nuclear imaging, and observing the universe.

Gamma Rays: Exact Definition

According to the Australian Radiation Protection and Nuclear Safety Agency (ARPaNSA), “a gamma ray is a packet of electromagnetic energy emitted by the nucleus of some radionuclides following radioactive decay. Gamma photons are the most energetic photons in the electromagnetic spectrum.”

The government agency goes on to define the measurement of gamma rays as greater than 100keV, which differs from NASA’s range of 200keV. This is because there is no hard line that defines each portion of the electromagnetic spectrum.

ARPaNSA describes in great detail the common sources of gamma radiation. This type of energy “is released from many of the radioisotopes found in the natural radiation decay series of uranium, thorium, and actinium, as well as being emitted by the naturally occurring radioisotopes potassium-40 and carbon-14.”

Where Do Gamma Rays Come From?

In their more common form, gamma rays occur during radioactive decay. This happens when the nucleus of an atom becomes too energized and releases its excess energy. Radioactive decay can occur with the nucleus releasing part of its composition (alpha decay) or without any change at all (gamma decay). Radioactive decay occurs randomly and can happen in any type of atom.

On a large scale, gamma rays are produced during nuclear fusion. This is the process of forcing four protons to fuse using immense temperature and pressure, creating an entirely new nucleus. The resulting nucleus has a mass that is smaller than the total mass of the four protons, causing an energy imbalance. That excess energy is emitted as gamma rays, which power massive celestial objects such as stars.

How Do You Create Gamma Rays?

Due to their entirely random nature, it’s hard to consistently create gamma rays through radioactive decay or nuclear fusion. However, scientists have discovered that they can artificially produce this type of radiation through nuclear fission. This is the process of splitting the nucleus of an atom into two equal parts. The new smaller nuclei have less total mass than the original nucleus, which allows them to produce gamma energy.

Scientists can synthesize nuclear fission using particle accelerators. These tools concentrate atoms toward each other at an incredible speed, causing them to collide. The resulting collision is enough to smash them into smaller pieces, causing the reaction. The Large Hadron Collider is the largest particle accelerator in the world, which can produce energy waves of 126geV or more.

Who Discovered Gamma Rays?

As early as 1896, scientists were researching the radioactivity of elements as they decayed. While studying the characteristics of radium, which produced varying degrees of alpha and beta rays that featured mass, the French chemist, Paul Villard, described radiation that was more powerful than discovered before. 

The reaction of radium salts escaping an aperture was analyzed through a thin sheet of lead. As two types of rays passed through, one was deflected by a magnetic field, and the other was not. The uncharged ray showed characteristics that made it unique to the other two and was named gamma for its position on the Greek alphabet.

It took several years to confirm gamma rays as a form of light energy, however. In 1914, the New Zealander physicist, Ernest Rutherford, continued to work with this type of radiation alongside beta rays, which were a form of particle. While directing the energy through crystal surfaces, Rutherford discovered that they reflected in the same way light does. This experiment definitively put gamma rays on the electromagnetic spectrum.

What are the Applications of Gamma Rays?

Vector diagram with the visible light spectrum
Gamma rays are a part of the electromagnetic spectrum, and they have tons of applications, from medicine to security.


Users in several markets can use gamma densitometers to measure the density and thickness of resources. Common sectors that use non-contact industrial sensors include mining, food, soap, and pulp and paper. Security sectors also use nuclear imaging to monitor the contents of shipping containers.


Despite its hazardous tendencies, practitioners in the medical industry use gamma rays for a variety of applications. Certain nuclear isotopes are ideal for eliminating bacteria which makes them reliable sterilizers. Oncologists also use this type of radiation to treat cancer and tumors in the brain.


Many of the universe’s largest sources of gamma rays are found in highly energetic celestial bodies. Gamma-ray bursts (GRB), the most powerful electromagnetic events ever recorded, can shine hundreds of times brighter than a supernova. While they typically last only a few seconds, GRBs can produce more energy than the sun will produce in its entire lifetime.

The origin of these phenomena is still under study. Currently, astronomers believe gamma-ray bursts result from the collision of massive space objects, but this is still unconfirmed. Because this energy dissipates in the Earth’s atmosphere, scientists use weather balloons and orbital satellites to observe it.  

Examples of Gamma Rays in the Real World

Container Security Initiative

In 2002, the Department of Homeland Security launched the Container Security Initiative (CSI), a practice to protect the U.S. shipping industry from terrorist organizations. The CSI uses gamma ray radiography to pre-screen containers that are susceptible to terrorism. This allows homeland security to monitor cargo non-intrusively, increasing the efficiency and effectiveness of defense protocols.

Leksell Gamma Knife Surgery

Oncologists use a machine that directs several gamma rays to cancer cells within the brain. During a gamma knife surgery, the patient wears a surgically fixed helmet that keeps the target cell from moving. They enter the machine, which relies on over 200 radioactive cobalt sources to beam radioactive energy at the location. The gamma rays come from all these different sources so they don’t affect the surrounding cells as they meet at the target cell.

Fermi Gamma-ray Space Telescope

Astronomers at NASA use the Fermi Gamma-ray Space Telescope to observe related phenomena. The events that Fermi help researchers capture include galactic nuclei, pulsars, and dark matter. This massive observatory, launched into lower Earth orbit in 2008, also uses a special instrument to specifically monitor gamma-ray bursts and solar flares.

In September of its first active year, the telescope witnessed a GRB with the largest energy release ever recorded, having the power of nearly 9,000 supernovae.

Gamma Rays: Further Reading

As the most powerful source of light energy in the universe, gamma rays have the potential to harm us. However, with careful concentration, we can use this type of radiation to improve our lives. For more on how we use the energy of the electromagnetic spectrum, check out the articles below.

Frequently Asked Questions

How do gamma rays compare to infrared light?

Gamma rays have a significantly higher energy level than infrared; their electron voltage can measure 100 million times more powerful than infrared. Gamma rays also have a significantly quicker frequency, which allows them to penetrate most materials.

What are gamma rays used for?

Gamma rays are used in a variety of applications, including radiography, cancer treatment, and space observation.

Are gamma rays harmful?

Due to their ability to pierce through the human body, gamma rays can potentially cause us harm when exposed to them in large quantities.

Where are gamma rays found?

Common sources of gamma rays include the radioactive decay of atomic compositions and nuclear reactions in large celestial objects, including galactic nuclei, pulsars, quasars, and gamma-ray bursts.

What can stop gamma rays?

In laboratory settings, researchers use thick sheets of lead as a shield to slow or stop gamma rays.

What happens if gamma rays hit us?

If gamma rays hit us in a significant quantity, it would alter the composition of our cells. This could result in tissue damage, DNA alteration, and even death.

To top