Asteroids, Meteors & Comets

Asteroids, Meteors & Comets

Asteroids (or Planetoids)

» Asteroids are also known as minor planets.
» They are objects that revolve around the Sun.
» They are mostly found between the orbits of Mars and Jupiter. They are a belt of debris which failed to assemble into planets and keeps on revolving around the Sun. This has come to be called as 'asteroid belt'.
» More than 5000 asteroids have been identified.
» Asteroids may be spherical, elongated or irregular in shape.
» All asteroids rotate on their axis, every 5 to 20 hours. Certain asteroids may have satellites.
» Trojan asteroids are found in two clouds moving in the orbit of Jupiter, one moving ahead of it and the other moving behind it.
» Scientists believe that these asteroids occupy a place where a planet could have existed but was prevented from its formation by the disruptive gravitational force of the nearby giant planet, Jupiter.

Meteors and Meteorites

» Meteors and Meteorites are also called shooting stars.
» Meteors are fragments of rocks coming towards the earth, formed due to the collision of asteroids with one another.
» Meteors are usually small, and due to the heat produced by air resistance, burn up before they reach the Earth's surface.
» When meteors are large and do not burn up completely, they land on the Earth's surface and are known as Meteorites.
» All meteorites are believed to originate in the asteroid belt, where a sudden collision may send them towards the Earth and the Earth's gravity attracts them towards its surface.

Comets

» Visitors of the Solar System.
» Comets (the name derived from the Latin words Stella cometa meaning 'hairy star') are among the most spectacular and unpredictable bodies in the Solar System.
» Comets move around the Sun in regular orbits, but their orbits are elongated ellipses that it takes them hundreds and, sometimes even thousands of years to complete one revolution around the Sun.
» Comets are made up of frozen gases which hold together rocky and metallic materials.
» A comet becomes visible only when it travels close to the Sun.
» Its ice melts and the gas and dust is swept back into a tail.
» The tail always points away from the Sun. So when it is travelling away from the Sun it is led by its tail.

Features of a Comet

» A comet is characterized by a long luminous tail, which emits light.
» But this is visible only when the comet's orbit passes close to the Sun.
» When the comet travels close to the Sun, the ice melts to a head of gas called a Coma.
» The Sun's radiation sweeps this into a gas tail.
» Dust particles are also swept back to form a dust tail.