Stellar Explosions & Extreme Stars
Fast Radio Bursts
Fast radio bursts are millisecond flashes of radio waves from far outside our galaxy, and their sources are still being pinned down.
First reported in 2007, they are among the most active puzzles in radio astronomy.
- Observe
A very short pulse of radio waves, arriving at different times across the radio band.
- Measure
Arrival time, duration, brightness and how the pulse is spread out across frequencies.
- Model
Magnetar-based models are leading, with other proposals still being tested.
- Explain
Something compact and highly magnetic can emit a burst of radio waves in a millisecond.
What is it?
A fast radio burst (FRB) is an intense pulse of radio waves lasting a few milliseconds. Most come from other galaxies, so the pulse must be extraordinarily energetic to be detected here.
Some FRBs repeat and others have been seen only once. In April 2020, a burst of radio waves from a magnetar in our own galaxy, called SGR 1935+2154, gave strong evidence that at least some FRBs come from magnetars. Whether all of them do, and by what exact mechanism the bursts are made, is not settled.
How does it happen?
- Stage 1Compact source emits a radio pulseOrigin still debated
- Stage 2Pulse crosses ionized gasLow frequencies arrive later
- Stage 3Radio telescope records it
- Stage 4Analysis estimates distance and location
What do we actually observe?
- Radio pulse
- A burst lasting roughly a millisecond, brighter than the background across the observing band.
- Dispersion
- Free electrons along the path delay lower frequencies more than higher ones. The size of the delay, the dispersion measure, gives a rough guide to how much matter the pulse crossed and so its distance.
- Repetition
- Some sources send repeated bursts, which lets astronomers study them for years and locate the host galaxy precisely.
- Location
- Radio arrays such as ASKAP and CHIME with outriggers can localize bursts to individual galaxies.
How do scientists detect it?
- CHIME. A Canadian radio telescope with a huge field of view that detects a few bursts per day.
- ASKAP and MeerKAT. Arrays that pinpoint burst positions well enough to identify host galaxies.
- Parkes and FAST. Large single-dish telescopes; the first FRB reported in 2007 was found in archival Parkes data.
Why does it matter?
- They test models of magnetars and other extreme compact objects.
- Because the pulses cross intergalactic space, they can be used to weigh the ionized gas that lies between galaxies, which is otherwise hard to measure.
The SpaceWeatherTracker connection
The delay of radio pulses by ionized gas is the same plasma physics that affects radio signals crossing Earth's ionosphere and the solar wind. Radio astronomers must separate cosmic bursts from local interference and from the Sun's own radio bursts.
Related phenomena
Primary family: Stellar Explosions & Extreme Stars
Fast Radio Bursts: common questions
What is a fast radio burst?
A fast radio burst is a very brief, very bright flash of radio waves from a source far outside our galaxy.
How long does an FRB last?
Typically about a millisecond to a few milliseconds. Some repeating sources produce bursts that last longer.
Where do FRBs come from?
The evidence points to compact objects, and a burst in 2020 from a magnetar in our own galaxy supports magnetars as one source. The full picture is still being worked out.
Can FRBs be predicted?
Some repeating sources show periodic activity windows, but individual bursts generally cannot yet be predicted.