Comets in Space

What Is a Comet?

Comets in space are small, fragile, irregularly shaped bodies. Composed of a mixture of nonvolatile grains and frozen gases, they often resemble dirty snowballs. Moving in highly elongated paths around the sun, comets are very small in size relative to planets. Their diameters usually range from 2,460 feet or less to about 12 miles.(1) These celestial travelers consists of a solid nucleus (core) surrounded by a cloudy atmosphere called the coma and one or two tails. Some comets cannot be seen without a telescope because they are too small or too faint. When comets in space pass close to the sun, we are often able to see them because the gas and dust in their comas and tails reflect sunlight. Also, comets glow because their gases release energy absorbed from the sun.(2)

Perhaps the most famous comet to date is Comet Halley. This comet is visible to the naked eye every 75 to 76 years. Its earliest sightings were thought to be in 240 BC, but may have been as early as 466 BC.(3)

Famous Comets

Other recent well-known comets include Comet Shoemaker-Levy 9 and Comet Hale-Bopp. Between July 16 and July 22, 1994, more than 20 fragments from Comet Shoemaker-Levy collided with Jupiter. This was the first collision of two bodies in the Solar System to be recorded by the Hubble Space Telescope.(4) Holding the record for the longest period of naked-eye visibility is Comet Hale-Bopp. For 19 months (May 1996-November 1997), the intense brightness of this comet in space could be seen – probably because of its large size, which was estimated to be 25-50 miles across.(5)

Comets in Space – Where Else Would They Be?

Space Comets have served as namesake for earthly ventures like the 1950’s rock group, Bill Haley and the Comets; the Mercury Comet automobile of the 1960s and 1970s; and the Comet Cleanser, which was introduced in 1956. Lesser-known entities sporting the name “Comet” include a wooden roller coaster at Hersheypark in Hershey, Pennsylvania; a 1940s superhero from the comics; and the family dog on the television series, “Full House.” Then, of course, there is Santa’s reindeer, “Comet.” Just like the other comets in space, he blazes a trail across the night sky and transports us from the “ordinary” to the “extraordinary.”

Jason Hammond, Dynetics

Sources

1. http://www.solarviews.com/eng/comet/whatis.htm
2. http://www.nasa.gov/worldbook/comet_worldbook.html
3. D. W. Graham and E. Hintz (July 2010). "An Ancient Greek Sighting of Halley's Comet?". Journal of Cosmology. http://journalofcosmology.com/AncientAstronomy106.html. Retrieved 18 September 2008.
4. http://lifestyle.iloveindia.com/lounge/famous-comets-3558.html
5. http://amazing-space.stsci.edu/resources/fastfacts/comet-halebopp.php

 

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