Universe 

A Flickering X-ray Candle

The Crab Nebula, created by a supernova seen nearly a thousand years ago, is 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.


For More Information

http://www.nasa.gov/mission_pages/GLAST/news/crab-nebula-surprise.html


Credits

Scott Wiessinger (UMBC): Animator
Scott Wiessinger (UMBC): Narrator
Scott Wiessinger (UMBC): Producer
Colleen Wilson-Hodge (NASA/MSFC): Scientist
Francis Reddy (SPSYS): Writer
Please give credit for this item to:
NASA/Goddard Space Flight Center. However, each image should be credited as indicated above.

Science Paper:
http://iopscience.iop.org/2041-8205/727/2/L40/pdf/apjl_727_2_40.pdf

Short URL to share this page:
http://svs.gsfc.nasa.gov/goto?10708

Missions:
Fermi Gamma-ray Space Telescope
Swift

Data Used:
Swift
Fermi/LAT
Fermi

This item is part of these series:
Narrated Movies
Fermi
Goddard Shorts
Astrophysics Stills
Astrophysics Features

Goddard TV Tape:
G2011-005 -- Crab Nebula Variability

Keywords:
SVS >> Gamma Ray
SVS >> HDTV
SVS >> Neutron Star
SVS >> Satellite
SVS >> X-ray
SVS >> Pulsar
SVS >> Swift
SVS >> Fermi
DLESE >> Narrated
SVS >> Supernova
SVS >> Star
SVS >> Nebula
NASA Science >> Universe