Difference between revisions of "Comet"
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(Copying images used in the Halley's Comet article) |
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[[Image:Halley1910a.jpg|right|thumb|300px|Halley's Comet on its 1910 appearance. This Yerkes Observatory photograph is highly enlarged; the comet would not have appeared this large or bright to the naked eye.]] | [[Image:Halley1910a.jpg|right|thumb|300px|Halley's Comet on its 1910 appearance. This Yerkes Observatory photograph is highly enlarged; the comet would not have appeared this large or bright to the naked eye.]] | ||
| − | [[Image:Yerkeshalley2.jpg|right|thumb|300px|Illustration of how Halley's Comet might have looked to a naked-eye observer standing on the ground of Yerkes observatory. Moon at left, Halley's at right. Relative sizes are correct and this is the way an extremely bright comet actually looks. Although its appearance suggests motion, comets do not swoop through the sky; their position changes slowly over many hours.]] | + | [[Image:Yerkeshalley2.jpg|right|thumb|300px|Illustration of how Halley's Comet might have looked to a naked-eye observer standing on the ground of Yerkes observatory in 1910. Moon at left, Halley's at right. Relative sizes are correct and this is the way an extremely bright comet actually looks. Although its appearance suggests motion, comets do not swoop through the sky; their position changes slowly over many hours.]] |
==See also== | ==See also== | ||
Revision as of 01:53, April 24, 2007
A comet is a ball of frozen gases, ice, and dust, typically having a diameter of less than five kilometers. A comet develops a tail composed of its constituent materials, in gaseous or liquid form, when it is close enough to the sun for some of the frozen material to melt. Comet tails can be millions of kilometers in length and always "point" away from the sun due to the pressure of the solar wind.
Comet orbits around the sun may be highly elliptical, rather than nearly circular (such as planets), which takes them out past the orbit of Pluto. Some of the mass of the comet will sublimate with each pass by the sun and after many passes the comet may no longer be active and be simply an asteroid.
Illustration of how Halley's Comet might have looked to a naked-eye observer standing on the ground of Yerkes observatory in 1910. Moon at left, Halley's at right. Relative sizes are correct and this is the way an extremely bright comet actually looks. Although its appearance suggests motion, comets do not swoop through the sky; their position changes slowly over many hours.