magnetar

Of all the neutron stars in the cosmos, a rare few are wrapped in magnetic fields so violent they almost defy description. A magnetar is a young neutron star with a magnetic field a thousand trillion times stronger than Earth's — the strongest magnets known to exist anywhere in the universe. Bring one within halfway to the Moon and its field would wipe every credit card and hard drive on Earth; get truly close and it would tear apart the atoms in your body.

How strong is that, really? Earth's magnetic field is about half a gauss; a fridge magnet, around 50 gauss; the strongest steady magnets humans have built, a few hundred thousand gauss. A magnetar's field reaches roughly a thousand trillion gauss — so intense it warps the shape of atoms and the rules of the vacuum itself. That energy does not sit quietly. Stresses in the field crack the neutron star's rigid crust in 'starquakes', unleashing flashes of X-rays and gamma rays. In 2004 a single giant flare from a magnetar 50,000 light-years away briefly outshone every other source in the sky in gamma rays and disturbed Earth's upper atmosphere.

Magnetars are short-lived show-offs: the colossal field decays over only thousands of years, so they make up a small fraction of neutron stars at any time. They are leading suspects behind some of the universe's most enigmatic signals, including fast radio bursts — millisecond blasts of radio energy from across the cosmos, at least some of which now seem to come from magnetars. They are a vivid reminder that a neutron star's magnetism, not just its gravity, can be a force of staggering power.