The Jupiter Trojans are a large group of objects that share the orbit
of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan
librates around one of the planet's two Lagrangian points of stability,
L4 and L5, that respectively lie 60° ahead of and behind the planet in
its orbit. Trojan asteroids are distributed in two elongated, curved
regions around these Lagrangian points with an average semi-major axis
of about 5.2 AU. The first Trojan, 588 Achilles, was discovered in 1906
by the German astronomer Max Wolf. A total of 2,909 Jupiter Trojans
have been found as of January 2009. The name "Trojans" derives from the
fact that, by convention, they each are named after a mythological
figure from the Trojan War. The total number of Jupiter Trojans larger
than 1 km is believed to be about 1 million, approximately equal to the
number of asteroids larger than 1 km in the main asteroid belt Like
main belt asteroids, Trojans form families. Jupiter Trojans are dark
bodies with reddish, featureless spectra. No firm evidence of the
presence of water, organic matter or other chemical compounds has been
obtained. The Trojans' densities (as measured by studying binaries or
rotational lightcurves) vary from 0.8 to 2.5 g·cm−3. Trojans are
thought to have been captured into their orbits during the early stages
of the Solar System's formation or slightly later, during the migration
of giant planets.
Read the rest of this article:
<http://en.wikipedia.org/wiki/Jupiter_Trojan>
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Today's selected anniversaries:
1153:
Malcolm IV became King of Scotland at the age of twelve.
<http://en.wikipedia.org/wiki/Malcolm_IV_of_Scotland>
1703:
Russian Tsar Peter I founded Saint Petersburg after reconquering the
Ingrian land from Sweden during the Great Northern War.
<http://en.wikipedia.org/wiki/History_of_Saint_Petersburg>
1937:
The Golden Gate Bridge , at the time the world's longest suspension
bridge span, connecting the San Francisco to Marin County, California,
opened.
<http://en.wikipedia.org/wiki/Golden_Gate_Bridge>
1942:
Czech resistance fighters in Nazi-occupied Prague ambushed and mortally
wounded Reinhard Heydrich, the chief of Reich Security Main Office and
the Protector of Bohemia and Moravia.
<http://en.wikipedia.org/wiki/Operation_Anthropoid>
1995:
Actor Christopher Reeve suffered a cervical spinal injury after being
thrown from his horse during the cross country portion of an eventing
competition held in Culpeper, Virginia, paralyzing him from the neck
down.
<http://en.wikipedia.org/wiki/Christopher_Reeve>
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Wiktionary's word of the day:
incubus (n):
1. An evil spirit supposed to oppress people while asleep, especially
to have sex with women as they sleep.
2. A feeling of oppression during sleep; night terrors, a
nightmare.
3. Any oppressive thing or person; a burden
<http://en.wiktionary.org/wiki/incubus>
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Wikiquote quote of the day:
The more clearly we can focus our attention on the wonders and
realities of the universe about us the less taste we shall have for the
destruction of our race. Wonder and humility are wholesome emotions,
and they do not exist side by side with a lust for destruction.
--Rachel Carson
<http://en.wikiquote.org/wiki/Rachel_Carson>