A Magnetic Surprise in the Stars

Astronomers have detected a strong magnetic field emanating from a star that computer models say shouldn't be able to produce one. The field is coming from a star called AB Aurigae--located about 460 light-years away--and its existence lends further credence to one of the more bizarre astronomical discoveries in recent years.

Powerful magnetic fields aren't easy for stars to generate. Until now, astronomers assumed that they only arose inside the fierce internal furnaces of hot, young stars much larger than the sun, or from the violent interaction between two closely orbiting stars in a binary system. Neither situation is true for AB Aurigae. The star is only about 2.7 times the mass of our sun, which should make it too small and cool to produce a strong magnetic field. But when a team led by Manuel Guedel of the Paul Scherrer Institute in Villigen, Switzerland, used the European Space Agency's orbiting XMM-Newton x-ray observatory to scan the young star, they picked up an x-ray signal, evidence of strong magnetism. What's more, AB Aurigae's x-ray, optical, and ultraviolet radiation all vary in intensity during the same 42-hour cycle, meaning the star itself is the only possible x-ray source.