A Flickering X-ray Candle

  • Released Wednesday, January 12, 2011
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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.

A short narrated video about the Crab Nebula's variability.

Credit: NASA/Goddard Space Flight Center

Watch this video on the NASAexplorer YouTube channel.

For complete transcript, click here.

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.

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.

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.

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

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. No Labels.Credit: NASA/Goddard Space Flight Center

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. No Labels.

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

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

Graph of Crab Nebula variablity with low-resolution "pixel" view of Crab Nebula.Credit: NASA/Goddard Space Flight Center

Graph of Crab Nebula variablity with low-resolution "pixel" view of Crab Nebula.

Credit: NASA/Goddard Space Flight Center

Artist interpretation of Crab supernova.Credit: NASA/Goddard Space Flight Center

Artist interpretation of Crab supernova.

Credit: NASA/Goddard Space Flight Center

For More Information

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

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NASA/Goddard Space Flight Center. However, each image should be credited as indicated above.

This page was originally published on Wednesday, January 12, 2011.
This page was last updated on Wednesday, May 3, 2023 at 1:53 PM EDT.

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  • Crab Nebula Variability (ID: 2011005)
    Tuesday, January 25, 2011 at 5:00AM
    Produced by - Robert Crippen (NASA)

Related papers

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

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

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