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Fermi Traces a Celestial Spirograph

NASA's Fermi Gamma-ray Space Telescope orbits our planet every 95 minutes, building up increasingly deeper views of the universe with every circuit. Its wide-eyed Large Area Telescope (LAT) sweeps across the entire sky every three hours, capturing the highest-energy form of light -- gamma rays -- from sources across the universe. These range from supermassive black holes billions of light-years away to intriguing objects in our own galaxy, such as X-ray binaries, supernova remnants and pulsars.

Now a Fermi scientist has transformed LAT data of a famous pulsar into a mesmerizing movie that visually encapsulates the spacecraft's complex motion.

Pulsars are neutron stars, the crushed cores of massive suns that destroyed themselves when they ran out of fuel, collapsed and exploded. The blast simultaneously shattered the star and compressed its core into a body as small as a city yet more massive than the sun. One pulsar, called Vela, shines especially bright for Fermi. It spins 11 times a second and is the brightest persistent source of gamma rays the LAT sees.

The movie renders Vela's position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT's field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT's vision. The movie tracks both Vela's position relative to the center of the LAT's field of view and the instrument's exposure of the pulsar during the first 51 months of Fermi's mission, from Aug. 4, 2008, to Nov. 15, 2012.

The pattern Vela traces reflects numerous motions of the spacecraft. The first is Fermi's 95-minute orbit around Earth, but there's another, subtler motion related to it. The orbit itself also rotates, a phenomenon called precession. Similar to the wobble of an unsteady top, Fermi's orbital plane makes a slow circuit around Earth every 54 days.

In order to capture the entire sky every two orbits, scientists deliberately nod the LAT in a repeating pattern from one orbit to the next. It first looks north on one orbit, south on the next, and then north again. Every few weeks, the LAT deviates from this pattern to concentrate on particularly interesting targets, such as eruptions on the sun, brief but brilliant gamma-ray bursts associated with the birth of stellar-mass black holes, and outbursts from supermassive black holes in distant galaxies.

The Vela movie captures one other Fermi motion. The spacecraft rolls to keep the sun from shining on and warming up the LAT's radiators, which regulate its temperature by bleeding excess heat into space.

Watch this video on YouTube.

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Another multimedia item related to this story:
     Fermi's LAT Instrument (id 20122)
More information on this topic available at:
http://www.nasa.gov/mission_pages/GLAST/news/spirograph.html

The Vela pulsar outlines a fascinating pattern in this movie showing 51 months of position and exposure data from Fermi's Large Area Telescope (LAT). The pattern reflects numerous motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, the manner in which the LAT nods north and south on alternate orbits, and more. The movie renders Vela's position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT's field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT's vision. Better knowledge of how the LAT's sensitivity changes across its field of view helps Fermi scientists better understand both the instrument and the data it returns. Credit: NASA/DOE/Fermi LAT Collaboration    The Vela pulsar outlines a fascinating pattern in this movie showing 51 months of position and exposure data from Fermi's Large Area Telescope (LAT). The pattern reflects numerous motions of the spacecraft, including its orbit around Earth, the precession of its orbital plane, the manner in which the LAT nods north and south on alternate orbits, and more. The movie renders Vela's position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT's field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT's vision. Better knowledge of how the LAT's sensitivity changes across its field of view helps Fermi scientists better understand both the instrument and the data it returns.

Credit: NASA/DOE/Fermi LAT Collaboration

For complete transcript, click here.
Duration: 1.1 minutes
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This image compresses the Vela movie sequence into a single snapshot by merging pie-slice sections from eight individual frames. Credit: NASA/DOE/Fermi LAT Collaboration    This image compresses the Vela movie sequence into a single snapshot by merging pie-slice sections from eight individual frames.

Credit: NASA/DOE/Fermi LAT Collaboration

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The LAT's sensitivity to gamma rays is greatest in the center of its wide field of view and decreases toward the edge. LAT scientists regard the effective limit of the instrument's field of view to be 78.5 degrees (red circle) from its center. Credit: NASA/DOE/Fermi LAT Collaboration    The LAT's sensitivity to gamma rays is greatest in the center of its wide field of view and decreases toward the edge. LAT scientists regard the effective limit of the instrument's field of view to be 78.5 degrees (red circle) from its center.

Credit: NASA/DOE/Fermi LAT Collaboration

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Final still from video. Credit: NASA/DOE/Fermi LAT Collaboration    Final still from video.

Credit: NASA/DOE/Fermi LAT Collaboration



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Original frame sequence. Credit: NASA/DOE/Fermi LAT Collaboration    Original frame sequence.

Credit: NASA/DOE/Fermi LAT Collaboration


Duration: 33.4 seconds
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Short URL to This Page:http://svs.gsfc.nasa.gov/goto?11205
Animation Number:11205
Completed:2013-02-07
Animator:Eric Charles (SLAC National Accelerator Laboratory) (Lead)
Video Editor:Scott Wiessinger (USRA)
Producer:Scott Wiessinger (USRA)
Scientist:Eric Charles (SLAC National Accelerator Laboratory)
Writer:Francis Reddy (Syneren Technologies)
Platforms/Sensors/Data Sets:Fermi/LAT
 Fermi
Series:Narrated Movies
 Astrophysics Visualizations
 Astrophysics Stills
 Astrophysics Features
Goddard TV Tape:G2013-022 -- Fermi Vela Cosmic Spirograph
Please give credit for this item to:
NASA's Goddard Space Flight Center. However, individual items should be credited as indicated above.
 
Keywords:
SVS >> Gamma Ray
SVS >> HDTV
SVS >> Music
SVS >> Neutron Star
SVS >> Astrophysics
SVS >> Pulsar
SVS >> Edited Feature
SVS >> Space
SVS >> Fermi
SVS >> Star
 
 


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Many of our multimedia items use the GCMD keywords. These 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

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