Universe ID: 10708

A Flickering X-ray Candle

Released on January 12, 2011

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.

NASA's Chandra X-ray Observatory reveals the complex X-ray-emitting central region of the Crab Nebula. This image is 9.8 light-years across. Chandra observations were not compatible with the study of the nebula's hard X-ray variations.

Credit: NASA/CXC/SAO/F. Seward et al.

X-ray data from NASA's Fermi, RXTE, and Swift satellites and the European Space Agency's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) confirm that the Crab Nebula's output has declined about 7 percent in two years at energies from 15,000 to 50,000 electron volts. They also show that the Crab has brightened or faded by as much as 3.5 percent a year since 1999. Fermi's Large Area Telescope (LAT) has detected powerful gamma-ray flares (magenta lines) as well.

Credit: NASA/Goddard Space Flight Center

This view of the Crab Nebula in visible light comes from the Hubble Space Telescope and spans 12 light-years. The supernova remnant, located 6,500 light-years away in the constellation Taurus, is among the best-studied objects in the sky.

Credit: NASA/ESA/ASU/J. Hester

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/10708

Missions:
Fermi Gamma-ray Space Telescope
RXTE
Swift

Data Used:
Fermi
Swift
Fermi/LAT
Note: While we identify the data sets used in these visualizations, we do not store any further details nor the data sets themselves on our site.

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 >> HDTV
SVS >> Neutron Star
SVS >> Satellite
SVS >> X-ray
GCMD >> Earth Science >> Spectral/Engineering >> Gamma Ray
SVS >> Pulsar
SVS >> Swift
SVS >> Fermi
DLESE >> Narrated
SVS >> Supernova
SVS >> Star
SVS >> Nebula
SVS >> RXTE
NASA Science >> Universe

GCMD keywords can be found on the Internet with the following citation: Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0