magnet + star

The term magnetar was coined by Robert Duncan and Christopher Thompson in 1992 to describe a type of neutron star with an extraordinarily powerful magnetic field. A neutron star is the collapsed core of a massive star that has exploded as a supernova — a sphere roughly 20 kilometers across but containing more mass than the sun. A magnetar is a neutron star whose magnetic field reaches 10^15 gauss, a quadrillion times stronger than Earth's field.

Duncan and Thompson proposed magnetars to explain soft gamma repeaters (SGRs) — objects that emit intense, repeated bursts of gamma rays. The 1979 event known as the March 5 burst, from SGR 0526-66 in the Large Magellanic Cloud, was the most intense burst of gamma rays ever recorded from outside the solar system at that time. It briefly overwhelmed the detectors on multiple spacecraft. The source had to be phenomenally powerful and phenomenally small.

On December 27, 2004, SGR 1806-20 produced a gamma-ray flare so powerful that it measurably compressed Earth's magnetosphere from 50,000 light-years away. The energy released in 0.2 seconds was more than the sun produces in 250,000 years. If this magnetar had been within 10 light-years of Earth, the flare would have stripped the ozone layer.

The word itself is simple — magnet plus star, a compound any English speaker can parse. But the simplicity of the name disguises the extremity of the object. A teaspoon of magnetar material weighs a billion tons. The magnetic field would erase your credit cards from halfway across the solar system. The magnetar is named like a household object but behaves like a weapon of cosmic scale.