Comet 17P/Holmes (November 2007)

A Celestial Surprise Produces a Strange Sight Comets are small bodies in the solar system composed of rock, ice, and dust.  They are like chunks of dirty ice the size of a small town traveling around the Sun in a wobbly, eccentric orbit.  When comets get close to the Sun, some of their surface ice and dust is vaporized and blown into space by the solar wind. This material becomes visible as a comet's characteristic glowing head and tail.    Comet 17P/Holmes (Fig. 1) is an obscure comet that orbits the Sun inside Jupiter's orbit (Fig. 2). It is normally 25,000 times fainter than the faintest star visible to the unaided eye.  For unknown reasons, on 2007 October 24, Comet 17P/Homes suddenly brightened almost 400,000 times within a few hours and became visible to the unaided eye.  Given the solar system's immense time scale, this event is analogous to an explosion.  The result was one of strangest objects to appear in the night sky (Fig. 1).		Technical Notes for Fig. 1. Camera: Canon Digital Rebel digital SLR camera with Sigma 70-200 mm telephoto zoom lens (zoomed out to maximum) and Sigma 2X teleconverter. Telescope mount: camera mounted directly on Losmandy GM-8 equatorial mount with digital clock drive, tracking unguided. Exposure: sequence of 16 exposures of 75 seconds each at f/5.6 with ISO 800 setting. Processing: aligned and stacked with Registax program; color correction, contrast adjustment, and cropping with Photoshop. ( back to home page)
Fig. 1.  Comet 17P/Holmes in the night sky over our house in Cockeysville, Maryland on the night of 2007 November 7 at approximately 10:45 pm EST (Nov 8 at 03:45 UTC).  The comet appeared to be approximately half of the Moon's apparent size.  Unlike other comets, there was no readily visible tail.
Fig. 2.  Diagram of the relative orbital positions of Comet 17P/Holmes and the inner planets of the solar system.  (Source: NASA Jet Propulsion Laboratory)

 back to home page