The story of a magnetar
Magnetars are a type of neutron star, which is the core of a massive star that devoured all its fuel, collapsed under its own weight and then exploded as a supernova. Magnetars are also often thought of as the most powerful magnets in the cosmos, with magnetic fields up to approximately 5,000 trillion times that of the Earth's. Astronomers have discovered less than two-dozen magnetars so far. The explosions that give birth to neutron stars, including magnetars, crush them into some of the densest objects known, second only to black holes. A neutron star often packs as much mass as a half-million Earths within a diameter of only 12 miles, and a teaspoonful of neutron star matter would weigh about 1 billion tons on Earth, approximately twice the combined weight of all the cars in the United States. This extraordinary mass gives a neutron star a powerful gravitational field, and a projectile would need to fly at about half the speed of light to escape from a neutron star’s surface. They can also spin as fast as the blades of a kitchen blender, up to 43,000 revolutions per minute. Past studies revealed hundreds of neutron stars can undergo changes in speed, in which the stars suddenly whirled faster. Now for the first time, scientists have discovered that neutron stars can abruptly slow down too.