comets, asteroids, meteoroids - astronomy - heath
When a comet gets close enough to the sun, the energy in the sunlight turns the ice into gas, releasing gas and dust. Clouds of gas and dust form a fuzzy outer layer called a coma.
A comet's coma has a solid inner core called a nucleus. The nucleus has a diameter of 1 km-100 km The nucleus and coma (the comet's head) is the brightest part of a comet due to it being a reflection of the Sun's light.
Asteroids
A small, rocky object that orbits the sun Most are located in a band between the orbits of Mars and Jupiter (Asteroid Belt) Asteroids are strongly influenced by the gravity of Jupiter.
Hundreds of thousands of asteroids have been discovered within the Solar System. 136,000 have orbits known well enough to be given official numbers. Of these, some 13,500 have official names.
About 90% of asteroids lie in the asteroid belt between Mars and Jupiter. The asteroid belt contains about 100,000 asteroids more than one kilometer across.Distance between asteroids is much larger than the size of an asteroid. This distance is not evenly distributed. Some asteroids can have their own moons.
Near Earth Asteroids These objects have orbits that are pass close by that of Earth. Asteroids that actually cross Earth's orbital path are known as Earth-crossers.
As of June 19, 2013, 10,003 near-Earth asteroids are known and the number over 1 kilometer in diameter is thought to be 861, with 1,409 classified as potentially hazardous asteroids - those that could pose a threat to Earth.
The comet's tail...As a comet approaches the sun and heats up, some of the gas and dust stream outward, forming a tail. The name "comet" means "long haired star" in Greek.
Most comets have two tails, a gas tail and a dust tail. Both tails usually point away from the sun due to the force of solar wind from the sun. A comet's tail can be more than 100 million kilometers long.
Meteors... When a meteoroid enters Earth's Atmosphere, friction with the air creates heat and produces a streak of light in the sky- a meteor.
Small meteors burn up in Earth's Thermosphere but most burn up in Earth's Mesosphere. Another name for Meteors are Shooting Stars. Meteor Shower occurs when a large number of meteors enter Earth's atmosphere in a short amount of time.
Astronomers think that there is not a 5th terrestrial planet due to the gravitational effect that Jupiter has on the asteroid belt.
Some astronomers believe a planet did form in this area (Artemis) but Jupiter ejected it. This can explain why Mars has a low mass.
Meteoroids... A meteoroid is a chunk of rock or dust in space. Meteoroids come from Comets or Asteroids.
Some form when asteroids collide in space; others form when a comet breaks up and creates a cloud of dust that continues to move across the solar system. Most meteoroids are tiny, between the size of a grain of sand and a pebble. Any natural space debris smaller than 100m is considered a meteoroid.
The origin of comets... Most comets are found in one of two distant regions of the solar system- the Kuiper belt and the Oort cloud.
The Kuiper Belt is a doughnut shaped region that extends from beyond Neptune's orbit to about 100 times Earth's distance from the sun. The Oort Cloud is a spherical region of comets that surrounds the solar system out to more than 1000 times the distance between Pluto and the sun.
Meteorites... If the meteoroid is large enough, it may not burn up completely. Meteoroids that pass through the atmosphere and hit Earth's surface are called meteorites.
Three Types Stony: similar to Earth rocks; carbon. 95% Iron: distinctive metallic appearance. 4% Stony-Iron: rare; contains iron and stone. 1%
Trojan Asteroids Two groups of asteroids precede and follow Jupiter on its orbit. They are called the Trojan asteroids (named after Homeric heroes)
Trojan Asteroids are kept from straying by the combined gravity of Sun and Jupiter. Jupiter has some 1800 known Trojan asteroids (1100 Greeks and 700 Trojans).
Comets
are loose collections of ice,dust, and/or rock particles whose orbits are usually very long, narrow ellipses. You can think of a comet as a "dirty snowball."
CARBON asteroids - dark in color SILICATES asteroids - look like Earth rocks IRON & NICKEL asteroids - rarest, shiny, metallic
classified by their composition
