On the basis of the new definition of planet given by the IAU (International Astronomical Union), the world’s top institution on space science research, leading astronomers participating in IAU’s meet at Prague (Czech Republic) on August 24, 2006, declared that Pluto would no longer remain a planet.
Under the IAU’s new guidelines, the number of planets in the Solar System has thus been reduced from nine to eight. Its merits mentioning here that, prior to this decision, Pluto had been holding the planetary status since its discovery in 1930 by Clyde Tombaugh.
Now, with the omission of Pluto from the Solar System , its membership has been restricted to the eight “classical” planets, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Pluto Gets a Numerical Denomination
Weeks after it was demoted to a sub – Planetary status, Pluto was given a new name to reflect its new status as a dwarf planet in September 2006. The former 9th planet was assigned the asteroid number 134340 by the Minor Planet Centre (MPC), the official organization responsible for collecting data about asteroids and comets in our Solar System.
Pluto’s companion satellites, Charon, Nix and Hydra are considered part of the same system and will not be assigned separate asteroid numbers. Instead, they will now be called 134340 I, II and III respectively.
Before loosing its planetary status on 24th August, 2006 Pluto was the outermost planet of the Solar System.
Asteroids are also known as the 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, ever 5 to 20 hours. Certain asteroids may have satellites.
Trojan asteroids are found in to cloud 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 exist 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 toward the Earth and the Earth’s gravity attracts them towards its surface.
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 aComet
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.