Magnetar Formation Mystery Solved?
Magnetars are the bizarre super-dense remnants of supernova explosions. They are the strongest magnets known in the Universe — millions of times more powerful than the strongest magnets on Earth.
When a massive star collapses under its own gravity during a supernova explosion it forms either a neutron star or black hole. Magnetars are an unusual and very exotic form of neutron star. Like all of these strange objects they are tiny and extraordinarily dense — a teaspoon of neutron star material would have a mass of about a billion tonnes — but they also have extremely powerful magnetic fields. Magnetar surfaces release vast quantities of gamma rays when they undergo a sudden adjustment known as a starquake as a result of the huge stresses in their crusts.
The Westerlund 1 star cluster, located 16 000 light-years away in the southern constellation of Ara (the Altar), hosts one of the two dozen magnetars known in the Milky Way.
“In our earlier work (eso1034) we showed that the magnetar in the cluster Westerlund 1 (eso0510) must have been born in the explosive death of a star about 40 times as massive as the Sun. But this presents its own problem, since stars this massive are expected to collapse to form black holes after their deaths, not neutron stars. We did not understand how it could have become a magnetar,” says Simon Clark, lead author of the paper reporting these results.