artist rendition of an explosion in space

Everything About Gamma-Ray Bursts

September 7, 2022 - Emily Newton

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Thought to happen when stars collapse into black holes, gamma-ray bursts are massively energetic explosions — which scientists believe are likely the strongest and brightest explosions to occur since the Big Bang.

Even the shortest gamma-ray bursts can emit more energy than the sun will produce in its entire 10 billion-year existence.

So far, scientists have only observed these gamma-ray bursts in distant galaxies, far from the Milky Way. Scientists believe that because gamma-ray bursts are so energetic and so infrequent — and because they are only detected in far-away galaxies — they’re likely to be extremely rare cosmic events.

These gamma-ray bursts and their origins are one of the biggest mysteries in high-energy astronomy. 

What Are Gamma-Rays and Gamma-Ray Bursts?

Gamma rays are a type of electromagnetic radiation and the most energetic form of light. These rays consist of the shortest wavelength electromagnetic waves, shorter than those of other types of electromagnetic radiation — like X-rays, UV light and microwaves.

A gamma-ray burst (or GRB) is a powerful explosion of these rays.

Individual bursts can vary significantly in duration — lasting just a few milliseconds or as long as several hours. Most bursts are “long bursts,” which last longer than two seconds. A smaller portion of bursts are short bursts that last less than two seconds. 

Some bursts are ultra-long bursts, and last longer than 10,000 seconds (166 minutes or 2.7 hours). Scientists have only identified a small number of these ultra-long bursts to date.

When a GRB occurs, it briefly provides the brightest source of gamma-ray photos in the universe. 

After the initial burst of gamma rays usually comes the emission of longer-wavelength electromagnetic radiation, like X-rays.

What Causes Gamma-Ray Bursts?

Scientists believe that the bulk of GRBs originate from the collapse of stars — specifically large, fast-spinning stars that contain low amounts of metal — into black holes during the final stages of their evolution. 

This collapse, called a hypernova or collapsar, would cause matter near the star’s core to plummet towards the star’s center and form an accretion disk — a highly energetic, extremely bright disk of diffuse matter. 

This matter falls into the newly formed black hole, creating a pair of relativistic jets — beams of matter accelerated to near-light speeds — along the black hole’s rotational axis. These jets blast through the surface of the collapsing star, releasing energy that radiates as a gamma-ray burst. 

In some models, the black hole is instead a magnetar, a type of neutron star that has an extremely powerful magnetic field. Otherwise, however, the model remains mostly the same.

The collapsar model may not be able to explain all types of gamma-ray bursts. There’s evidence that short gamma-ray bursts, with a duration of less than two seconds, occur in systems with no star formation and no massive stars. Gamma-ray bursts that emerge from these systems may instead come from the merger of two neutron stars and the formation of a black hole. 

Scientists have also proposed numerous alternative theories for the origin of gamma-ray bursts. Possible origins include the merger of neutron stars and black holes, the collapse of neutron stars and the evaporation of primordial black holes — a hypothetical form of ancient black hole that formed soon after the Big Bang.

The History of Gamma-Ray Bursts

Gamma-ray bursts have only been to known to astronomers since the late 1960s. The first gamma-ray burst was observed unintentionally by Vela satellites — a group of U.S.-designed satellites built to detect nuclear testing at the height of the Cold War.

It wouldn’t be for another 20 years before astronomers began actively looking for gamma-ray bursts. In 1991, scientists launched the Compton Gamma Ray Observatory by way of the Burst and Transient Source Experiment (BATSE), a monitoring program that aimed to detect and locate gamma-ray bursts from anywhere in the sky. 

The BATSE program detected roughly one gamma-ray burst per day and found that these bursts were evenly distributed across the sky — suggesting that they were happening everywhere in the universe, in many different types of galaxies, rather than concentrated in specific parts of the cosmos. 

The program also allowed scientists to begin classifying different types of gamma-ray bursts. Initially, astronomers identified two categories of gamma-ray bursts: those that lasted 2 to 30 seconds, and those that lasted less than two seconds. 

In the years since the launch of BATSE, scientists around the world have launched a number of other programs. 

These programs have identified a wider variety of gamma-ray bursts, including ultra-long bursts that last much longer than 30 seconds. Scientists are also developing new monitoring programs all the time that will allow them to more effectively track gamma-ray bursts, no matter where in the sky they occur.

Do Gamma Rays Threaten Life on Earth? 

The high levels of energy produced by GRBs is very likely to have destructive effects on life as we know it. In addition to the energy from the burst causing damage to organic material, gamma rays can also damage DNA, potentially leaving a long-lasting impact on life.

While scientists believe that GRBs occur all throughout the known universe, scientists haven’t yet detected a gamma-ray burst in or nearby the Milky Way. The closest observed gamma-ray burst was 130,000,000 light-years away.

If a GRB were to occur close enough to Earth — within a range of 5,000 to 8,000 light-years — and it was pointed directly at the planet, it could have devastating effects on ecosystems around the world. Astronomers agree that this event is pretty unlikely. At the very least, it would be unprecedented.

Potential Sources for GRBs in the Milky Way

There are a few star systems in the Milky Way, that are close to going supernova and could potentially produce a gamma-ray burst when they collapse — like Apep, a triple-star system that’s 8,000 light-years from Earth and contains a star on the verge of explosion. 

However, knowledge of gamma-ray bursts comes primarily from metal-poor galaxies that emerged during earlier phases of the universe’s evolution. It’s hard to know for certain if supernovae in more evolved galaxies with a greater abundance of metals, like the Milky Way, would also lead to gamma-ray bursts. 

All known candidates for gamma-ray burst generation in the Milky Way are also far enough away from the Earth that a resulting burst wouldn’t likely impact the planet. Even if a gamma-ray burst originated close enough to Earth to harm life, it would need to be at the correct orientation to actually impact the planet. 

While gamma-ray bursts likely cause serious damage to organic matter, we probably won’t have to worry about a burst impacting life on Earth any time soon.

Related High-Energy Phenomena

While gamma-ray bursts are intensely bright and energetic, they aren’t the only source of extremely energetic electromagnetic radiation that scientists have detected.

Gamma-ray hot spots, for example, are mysterious areas of space where electromagnetic fields accelerate charged particles, either protons or electrons, to immense speeds.

Some of these hot spots exist within the Milky Way galaxy. In 2021, a new detector on the Tibetan Plateau discovered a dozen sources of ultra-high-energy gamma rays inside the Milky Way. 

One ray had observed an observed energy level of 1.4 petaelectronvolts — a thousand times more energetic than the most energetic gamma-ray burst, which had an energy of one teraelectronvolt.

Like gamma-ray bursts, scientists don’t fully understand how or why these gamma-ray hot spots emerge. The new hot spots, however, suggest that they may have an origin in collapsed stars, somewhat similarly to the theories behind the generation of gamma-ray bursts.

The Mysteries Behind Gamma-Ray Bursts

While scientists have known about gamma-ray bursts since the late 1960s, they still don’t fully understand where these bursts come from. 

Programs around the world continue to regularly detect gamma-ray bursts, however, from almost everywhere in the cosmos — providing scientists with more information on these bursts, their characteristics and their potential origins.

Related phenomena, like gamma-ray hot spots, may provide scientists with additional help in determining how GRBs originate.

While gamma rays can cause serious damage to life, the Earth isn’t likely to experience a gamma-ray burst.

Revolutionized is reader-supported. When you buy through links on our site, we may earn an affiliate commision. Learn more here.


Emily Newton

Emily Newton is a technology and industrial journalist and the Editor in Chief of Revolutionized. She manages the sites publishing schedule, SEO optimization and content strategy. Emily enjoys writing and researching articles about how technology is changing every industry. When she isn't working, Emily enjoys playing video games or curling up with a good book.

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