[M1 in UV, Astro-1 mission] [PNG]

This is an early-release image of a young supernova remnant. This image was taken by UIT during Astro-1 and is shown here in false-color.

[M1 in Near UV, Astro-1] [PNG]

The Crab in the near UV light

[M1 in Far UV, Astro-1] [PNG]

The Crab in the far UV light

In 1054 AD, Chinese astronomers and Anasazi Indian artists (in present-day Arizona and New Mexico) recorded the appearance of a bright ``guest'' star in the heavens. Looking in the same part of the sky (in the constellation of Taurus the Bull), contemporary astronomers find a much fainter and more nebulous object. Number one in Charles Messier's catalog of fuzzy looking objects, the Crab Nebula is recognized today as the brightest supernova remnant in the sky. Approximately 940 years before the Crab attained its current appearance, a massive star exploded with the power of 400 billion Suns. It left behind a rapidly rotating neutron star and a cloud of ejected gases flying outwards at speeds of 1000 kilometers per second (or 2.2 million miles per hour). By observing at a variety of wavelengths, we can see these remnants of the explosion. At the highly energetic x-ray wavelengths, the embedded neutron star beams at us in the form of an x-ray pulsar. The surrounding nebulosity --- evident at x-ray, ultraviolet, and visible wavelengths --- traces electrons whirling in the presence of strong magnetic fields at speeds approaching the speed of light. The magnetically deflected electrons radiate photons in the form of synchrotron emission, similar to the radiation produced in synchrotron particle accelerators. Both the high-speed electrons and strong magnetic fields draw energy from the rapidly spinning pulsar. Currently rotating 30 times each second, the pulsar is gradually but inexorably spinning down --- its rotational energy being transferred to the high-speed electrons which radiate it away. By comparing the near and far-UV images of the Crab's synchrotron emission, researchers have found spatial variations in the ``ages'' of the electrons --- the ``younger'' and more energetic electrons being found closer to the pulsar.

Obtained on the Astro-1 Space Shuttle Mission (STS-35) with the Ultraviolet Imaging Telescope (UIT)


Hartmut Frommert
Christine Kronberg

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Last Modification: June 18, 1999