Stellar Explosions & Extreme Stars
Magnetars
Magnetars are neutron stars with the strongest magnetic fields known, powering bursts and giant flares.
A few dozen are known in the Milky Way, and one produced a radio burst in 2020 that links magnetars to fast radio bursts.
- Observe
Repeated X-ray and gamma-ray bursts from a slowly spinning neutron star.
- Measure
Burst energy, rotation period and how the spin slows.
- Model
Stresses in an ultra-strong magnetic field crack the crust and release energy.
- Explain
Magnetic energy, not spin, powers the star.
What is it?
A magnetar is a neutron star whose magnetic field is roughly a thousand trillion times stronger than Earth's. Instead of being powered by rotation, its emission is thought to come from the decay and rearrangement of that field. Astronomers see X-ray and gamma-ray bursts, and, rarely, giant flares.
How magnetars form is not settled. One leading idea is that they are born with unusually strong fields from the collapse of a fast-spinning core. A few dozen have been identified in the Milky Way.
How does it happen?
- Stage 1Neutron star with extreme magnetic field
- Stage 2Field stresses the crustTwisting and cracking
- Stage 3Magnetic energy is released
- Stage 4X-ray/gamma bursts or giant flare
What do we actually observe?
- Bursts
- Short bursts of X-rays and soft gamma rays, sometimes in clusters.
- Giant flares
- Extremely rare events far brighter than ordinary bursts. Three have been recorded in the Milky Way and the Large Magellanic Cloud, including SGR 1806-20 on 27 December 2004.
- Radio burst
- In April 2020, the magnetar SGR 1935+2154 emitted a radio burst detected by CHIME and STARE2 that resembled a fast radio burst.
How do scientists detect it?
- X-ray and gamma-ray satellites. Swift, Fermi, NICER and others catch bursts and track spin.
- Radio telescopes. Look for radio bursts and pulsations.
Why does it matter?
- Magnetars test how magnetic fields behave under extreme conditions.
- They are a leading candidate source for at least some fast radio bursts.
The SpaceWeatherTracker connection
Magnetars show how a magnetic field can dominate the physics of an entire star. The 2004 SGR 1806-20 giant flare briefly disturbed Earth's upper atmosphere, even though it came from tens of thousands of light-years away.
Related phenomena
Primary family: Stellar Explosions & Extreme Stars
Magnetars: common questions
How strong is a magnetar's magnetic field?
On the order of a thousand trillion gauss, compared with about half a gauss at Earth's surface.
Could a magnetar affect Earth?
The 2004 giant flare produced measurable effects on Earth's upper atmosphere from thousands of light-years away. A nearby magnetar would matter more, but none is known close by.