Gamma-Ray Bursts Could Wipe Out All Life, But Are Unlikely to Hit Earth

These cosmic explosions are so powerful that they could sterilize all life on Earth — or even vaporize the planet. Luckily, the chances of one happening in our solar system are slim.

By Max Bennett
Mar 18, 2024 1:00 PM
Gamma ray burst - NASA
Artist’s rendering of a gamma-ray burst. (Credit: NASA’S Goddard Spaceflight Center)


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Gamma rays are weightless, high-energy packets of electromagnetic radiation — the same stuff that makes up light. However, while visible light can comfortably light up a room, gamma rays can penetrate concrete, and cause serious damage to the human body as they pass through.

While we may assume we’re safe from the effects of gamma radiation, one particular cosmic phenomenon — gamma-ray bursts — poses a chilling question: What would happen if one of these massive spikes of radiation hit the Earth?

To answer that, we first need to explore what fuels the universe's brightest, most powerful explosion.

How Powerful Is a Gamma-Ray Burst?

These massive releases of energy are rivaled by few in terms of sheer ferocity. In just a few seconds, a gamma-ray burst releases more energy than our sun is capable of generating in the entirety of its lifetime, or 10 billion years.

To produce such a catastrophic energy projectile, an equally powerful explosion is in order, which is where gamma-ray bursts come from. As stars age, they slowly burn through the fuel that keeps them from collapsing in on themselves due to their gravity. In essence, a star is a gravity-bound explosion — when gravity eventually wins, the hot ball of gas is condensed into an even hotter, denser ball of gas, collapsing in on itself.

Some stars become red giants as energy from a hotter core drives expansion. This will be the fate of our sun. Others, however, are far more massive than anything in our solar system and will create violent implosions upon collapse; the result is a titanic blast called a supernova, and a black hole denser than anything else in the known universe. The collisions and violent mergers of superdense bodies called neutron stars can also lead to such black holes.  

Read More: Unraveling the Brightest Gamma Ray Burst of All Time

The Causes of a Gamma Ray Burst

In any such event, the result of the massive input of energy generated by a collapsing star is an equally massive output: a gamma-ray burst. That's because the magnetic fields of the contracting stars collect and concentrate leftover material at the poles (a superheated plasma), and then eject them into space as concentrated beams of energy.

Gamma-ray bursts can vary radically in both their severity and their duration. Some scientists believe our planet could be vaporized if one of these jets of energy were aimed directly at Earth, and occurred within a distance of 200 light years. Even elsewhere in the Milky Way, at greater distances, the radiation could still sterilize half of all life on Earth.

Fortunately, astronomers think that the chances of a gamma ray burst happening in our celestial backyard is slim: Since there are no stars within 200 light years of Earth that are fated to erupt in a gamma-ray burst, it's unlikely that we'll ever be in close enough range to suffer the consequences.

Read More: Researchers Find New High-Energy Gamma-Ray Sources in the Galaxy

Is Gamma Radiation Dangerous?

Still, even less intense exposure to these rays is indeed dangerous. Just as ultraviolet radiation, or UV rays, make sunscreen a necessity lest one risk skin cancer, gamma rays would also require a form of physical protection. Only instead of SPF 30, one would need to apply several inches of lead, the same material used to shield nuclear reactors. The potent gamma radiation would otherwise easily penetrate the skin and start stripping electrons from the atoms in our bodies.  

The infamous Chernobyl disaster of 1968 involved a catastrophic meltdown of the reactor once used to power the city of Pripyat. In addition to neutrons and high-energy alpha and beta particles, which have mass, the initial clean-up crew of the destroyed power plant was also faced with significant amounts of gamma radiation. As such, many suffered from significantly higher rates of leukemia and other cancers, in addition to direct “gamma burns” on the surface of the skin.  

A long-lasting gamma beam would have similar effects, but on the entire surface biosphere, sterilizing everything it touches. Like a cosmic disinfectant, it would destroy DNA and damage tissue much like a UV wand kills off germs on medical equipment. Virtually nothing above ground would survive, and ecosystems as we know them would be devastated. 

Fortunately, this doomsday scenario would only occur if Earth were directly in the relatively narrow path of the beam, and (again) only within the Milky Way. Yet there are precedents for a mass extinction event caused by such a burst — the long history of our planet makes this more statistically probable than you may think. 

Read More: Have Chernobyl Mutations Rewired Evolution?

Gamma-Ray Events Through the Ages  

Around 450 million years ago, during the Ordovician era, a sudden ice age is believed to have wiped out two thirds of animal life. (At the time, that mostly consisted of aquatic invertebrates like trilobites and graptolites.) It's known as the second most devastating extinction in our planet’s history, and some scientists believe, among other factors, that gamma-ray interference might be to blame.  

Earth’s atmosphere is an effective insulator, blocking out much of the high-energy radiation we get from the cosmos, but this doesn’t leave it unscathed. Exposure to gamma radiation can ionize oxygen and nitrogen, creating elevated levels of nitrous oxides. That's the same gas that creates the photochemical smog engulfing cities like Los Angeles, and it may have blocked out enough sun to cool the planet hundreds of millions of years ago.  

Plus, that radiation also depletes the ozone layer, causing carcinogenic UV rays to reach the surface. In the Montreal Protocol of 1992, governments around the world banned the use of chlorofluorocarbons, or CFCs, precisely due to their ozone-depleting effects. Without large-scale regulatory frameworks at their disposal, many of the inhabitants of the Ordovician simply perished. 

Such occurrences aren’t relegated to the distant past. In October of 2022, a wave of radiation washed through the solar system, more intense than anything observed before. Astronomers dubbed it the BOAT, the brightest of all time. Its source was an unusually close brush with a gamma-ray burst, a 1-in-10,000-year event, according to a 2023 study published in Astrophysical Research Letters

Fortunately for life on Earth, the confined nature of the beams means that a direct collision would be very unlikely. Nonetheless, the elusive nature of gamma-ray bursts ensures that they will continually inspire awe — and perhaps a bit of fear — of our cosmic backyard. 

Read More: How Will Life on Earth End?

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