Strange Rumblings of a Neutron Star

The Crab Nebula courtesy of NASA. Created by a supernova seen nearly a thousand years ago, it s one of the sky s most famous "star wrecks." For decades, most astronomers have regarded it as the steadiest beacon at X-ray energies, but data from orbiting observatories show unexpected variations, showing astronomers their hard X-ray "standard candle" isn t as steady as they once thought. From 1999 to 2008, the Crab brightened and faded by as much as 3.5 percent a year, and since 2008, it has faded by 7 percent. The Gamma-ray Burst Monitor on NASA s Fermi satellite first detected the decline, and Fermi s Large Area Telescope also spotted two gamma-ray flares at even higher energies. Scientists think the X-rays reveal processes deep within the nebula, in a region powered by a rapidly spinning neutron star -- the core of the star that blew up. But figuring out exactly where the Crab s X-rays are changing over the long term will require a new generation of X-ray telescopes. From NASA Goddard Space Flight Center