Stellar Explosions & Extreme Stars
Gamma-Ray Bursts
Gamma-ray bursts are brief, intense flashes of high-energy light from the most energetic explosions known.
They come from distant galaxies and appear from random directions, lasting from a fraction of a second to several minutes.
- Observe
A sudden gamma-ray flash from a random direction, followed by a fading afterglow.
- Measure
Satellites time and locate the flash; telescopes track the afterglow.
- Model
A narrow jet of matter moving close to the speed of light is launched by a newborn compact object.
- Explain
A star died or two compact objects merged, and a jet happened to point at us.
What is it?
A gamma-ray burst (GRB) is a sudden flash of gamma rays, the highest-energy form of light. Bursts are followed by a fading afterglow in X-ray, optical and radio light. Nearly all are from other galaxies, often billions of light-years away.
Astronomers usually sort bursts by duration. Bursts lasting longer than about two seconds, called long bursts, are linked to the deaths of some massive stars. Shorter bursts are linked at least in part to mergers of compact objects such as neutron stars, a link strengthened by the 2017 event that also produced gravitational waves. The line between the groups is not perfectly clean.
How does it happen?
- Stage 1Massive star collapses or compact objects merge
- Stage 2A central engine launches a jetNear the speed of light
- Stage 3Jet emits gamma raysThe prompt burst
- Stage 4Jet meets surrounding gasAfterglow fades over days
What do we actually observe?
- Gamma radiation
- A burst of gamma rays lasting from milliseconds to minutes, often with a spiky light curve.
- Duration
- The split at about two seconds is used to tell long and short bursts apart.
- Afterglow
- X-ray, optical and radio light that fades over hours to weeks and lets astronomers pin down the host galaxy and distance.
How do scientists detect it?
- Fermi Gamma-ray Space Telescope. Its Gamma-ray Burst Monitor watches much of the sky at once.
- Neil Gehrels Swift Observatory. Swift finds bursts and rapidly points its X-ray and ultraviolet telescopes at them.
- Ground-based telescopes. Optical and radio telescopes follow the afterglow and measure distances.
Why does it matter?
- They probe the deaths of massive stars and the merging of neutron stars.
- Their brightness lets astronomers see events from the early universe.
- The gamma-ray burst GRB 221009A, detected in October 2022, was one of the brightest ever recorded, and it produced measurable disturbances in Earth's upper atmosphere.
The SpaceWeatherTracker connection
SpaceWeatherTracker tracks X-ray output from the Sun's flares because it changes Earth's upper atmosphere. Very intense gamma-ray events from beyond the Solar System can also disturb the ionosphere, although such events are rare.
Related phenomena
Primary family: Stellar Explosions & Extreme Stars
Gamma-Ray Bursts: common questions
What is a gamma-ray burst?
A gamma-ray burst is an extremely brief and intense flash of gamma rays from a distant galaxy, thought to come from the death of some massive stars or the merger of compact objects.
Could a gamma-ray burst harm Earth?
A burst in our own galaxy that pointed directly at Earth could affect the atmosphere, but no such nearby burst has been observed, and such an alignment is thought to be very rare.
How long does a gamma-ray burst last?
The main flash lasts from a fraction of a second to a few minutes. The afterglow can be detected for days to weeks.