gegenschein

Dictionary: ge·gen·schein

(gā'gən-shīn') pronunciation

n.
A faint glowing spot in the sky, exactly opposite the position of the sun. Also called counterglow.

[German : gegen, against (from Middle High German , from Old High German gegin) + Schein, light (from Middle High German schīn , from Old High German scīn , from scīnan, to shine).]

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Wordsmith Words: gegenschein

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(GAY-guhn-shyn)

noun
A faint oval patch of light directly opposite the sun in the night sky, caused by reflection of sunlight by dust particles. Also known as counterglow.

Etymology
From German Gegenschein, from gegen (against) + Schein (glow)

Pictures of gegenschein: swisseduc.ch/stromboli/volcano/photoastro/gegenschein-en.html.

Usage
"Orbiting Gemini astronauts carried out photographic experiments designed by Dr. Ney in 1965 to explain enigmatic phenomena like gegenschein and zodiacal light, faint glows found even in the darkest night sky." — Wolfgang Saxon; Edward P. Ney, 75; Searched the Skies for Cosmic Particles; The New York Times; Aug 12, 1996.

Britannica Concise Encyclopedia: gegenschein

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Oval patch of faint light exactly opposite the Sun in the night sky, so faint it can be seen only in the absence of moonlight, away from city lights, with the eyes adapted to darkness. It is lost in the light of the Milky Way except in February, March, April, August, September, and October. The gegenschein and the zodiacal light form the most notable parts of a band of very faint light along the ecliptic. Both phenomena are thought to be the result of the reflection of sunlight from interplanetary dust grains.

For more information on gegenschein, visit Britannica.com.

Columbia Encyclopedia: gegenschein

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gegenschein (gā'gənshīn') or counterglow, a slight brightening of the night sky in the region of the zodiac directly opposite the sun, i.e., 180° from the sun. Discovered by the Danish astronomer Theodor Brersen in 1854, its nature and cause are still unknown. It may be caused by reflection of sunlight by small dust particles that lie in the plane of the solar system. It is possible that these particles are part of a tail of the earth, extending away from the sun like the tail of a comet. The gegenschein is one of several sky glows, as is the zodiacal light.

Wikipedia: Gegenschein

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Gegenschein (German pronunciation: [ˈɡeːɡənʃaɪn] German for "counter shine"), is a faint brightening of the night sky in the region of the antisolar point.

1 Observation
2 Explanation
3 History
4 See also
5 References
6 External links

Observation

The gegenschein is so faint that it cannot be seen if there is any moonlight or light pollution, or if it falls in the vicinity of the Milky Way. The gegenschein appears as a softly glowing oval region a few degrees wide and 10–15° in length, oriented along the plane of the ecliptic.

Explanation

Like the zodiacal light the gegenschein is sunlight reflected by interplanetary dust. Most of this dust is orbiting the sun in about the ecliptic plane, with a possible concentration of particles at the L₂ Earth-Sun Lagrangian point.

It is distinguished from zodiacal light by its high angle of reflection of the incident sunlight on the dust particles. It forms a slightly more luminous, oval glow directly opposite the Sun within the band of luminous zodiacal light. The intensity of gegenschein is (relatively) enhanced because each dust particle is seen in full phase.^[1]

History

The gegenschein was first described by the French Jesuit astronomer and professor Esprit Pézenas (1692–1776) in 1730. Further observations were made by the German explorer Alexander von Humboldt during his South American journey from 1799 to 1803. It was also Humboldt who gave the phenomenon its German name Gegenschein.

The Danish astronomer Theodor Brorsen published the first thorough investigations of the gegenschein in 1854. He was also the first to observe that the Zodiacal light can embrace the complete sky, because under near-perfect conditions a feeble light bridge connecting the Zodiacal light and the gegenschein can be observed. Besides, Brorsen had already proposed the correct explanation for the gegenschein (interplanetary dust reflections).

References

^ Levasseur-Regourd, Anny-Chantal; Hiroichi Hasegawa (1991). Origin and Evolution of Interplanetary Dust. International Astronomical Union Colloquium. p. 159. ISBN 0-7923-1365-8.

External links

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	zodiacal light (in astronomy)
	Antisolar point
	Afterglow

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		Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more
		Wordsmith Words. © 2009 Wordsmith.org. All rights reserved. Read more
		Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more
		Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more
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