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Asteroids |
Trojan
asteroids |
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Asteroids,
also called minor planets or planetoids, are a class of astronomical objects.
The term asteroid is generally used to indicate a diverse group of small
celestial bodies in the solar system that orbit around the Sun. 'Asteroid'
(Greek for "star-like") is the most commonly used word in the English literature
for minor planets.Several hundred thousand asteroids have been discovered and
given provisional designations so far.They have been found inside Earth's orbit
to beyond Saturn's orbit. Most, however, are contained within a
main belt that exists
between the orbits of Mars and Jupiter.Much of our understanding about asteroids
comes from examining pieces of space debris that fall to the surface of Earth.
Scientists think that this debris may be the remains of an early planet, which
broke up early in the solar system. Several thousand of the largest asteroids in
this belt have been given names. Asteroids range in size from a few meters to
over 900 km across, and vary greatly in composition.
While breaking down larger asteroids into
smaller ones, collisions expose deeper layers of asteroidal material. If
asteroids were compositionally homogeneous, this would have no noticeable
result.
The asteroid designated
(323) Brucia, detected in
1891, was the first to be discovered by means of photography. |
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The
first asteroid to be given a non-mythological name was 20 Massalia, named
after the city of Marseilles. For some time only female (or feminized) names
were used; Alexander von Humboldt was the first man to have an asteroid
named after him, but his name was feminized to 54 Alexandra. This unspoken
tradition lasted until 334 Chicago was named; even then, oddly feminised
names show up in the list for years afterward.Several hundred thousand
asteroids have been discovered and given provisional
designations so far.Asteroids are rocky and metallic
objects that orbit the Sun but are too small to be
considered planets.An almost equally large population is
the Trojan asteroids, which are trapped in the two
Lagrangian points 60 degrees ahead of and behind Jupiter
in its orbit. There are twenty
six asteroids larger than 124 miles in diameter,
with hundreds of thousands of smaller asteroids.
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Stars and gas |
Asteroidbelt |
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More than 7000 asteroids have been discovered. Several
hundred more are discovered each year.The vast majority
of asteroids are grouped in the asteroid belt,
which is more like a loose grouping than a belt, and
lies between 1.8 and 4.5 A.U. Asteroids are small bodies
that are believed to be left over from the beginning of
the solar system 4600 million years ago.
Asteroids and comets have had a fundamental
impact on the development of Earth.
Two hundred years after the first asteroid was
discovered, asteroids can no longer be considered mere
points of light in the sky. Father Giuseppe Piazzi,
Discoverer of First Asteroid.The stunning
amount of forest devastation at Tunguska a century ago
in Siberia may have been caused by an asteroid. |
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