Science
Comet 71P/Holmes brightens a million times: See it in your local night sky | Comet 71P/Holmes brightens a million times: See it in your local night sky |
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| Written by William Atkins | |
| Sunday, 28 October 2007 | |
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For a star map of the periodic comet, go to the website of Sky & Telescope magazine: http://www.skyandtelescope.com/. Those sky gazers who have already viewed the comet have described it as a bright yellow-orange colored star. It appears unlike many other comets, such as Halley’s Comet and Hale-Bopp, which periodically appear in the night skies as a bright central core (nucleus) and a trailing tail. Those with binoculars and telescopes should see Comet 71P/Holmes as a definite shaped spherical body, rather than just a point of light, like with distant stars. Comet 71P/Holmes was discovered in November 6, 1892 by British astronomer Edwin Holmes (c. 1842-1919) while he was conducting astronomical research on the Andromeda Galaxy (M31). It did the same thing back then, reaching 5th magnitude while Holmes studied it. Holmes was awarded the Donohoe Comet Medal by the Astronomical Society of the Pacific for his discovery. The comet makes one orbit about the Sun every seven years or so. The solar system-based comet’s nearest approach to the Sun is about 200 million miles (322 million kilometers), whereas the Earth is about 93 million miles (150 million kilometers) away from the Sun. Its last closest approach to the Sun (what is called perihelion) was on May 4, 2007. Its next predicted perihelion is expected to be March 27, 2014. Astronomers have stated that before October 23rd it was a very dim 17th magnitude object (25,000 times too faint to see with the naked eye), but suddenly on October 23-24, 2007, it began to glow as a 7th magnitude object, reaching magnitude 2.8 in only a few hours. Such a change in magnitude (brightness) corresponds to about a one million-fold increase in brightness.
The big question is: Why did it suddenly change its brightness? Astronomers are still pondering that question, although some scientists speculate that such dramatic changes of luminosity is caused by the quick ejection of particles from the comet as it approaches the Sun—what is called “outgassing” by astronomers.
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