F3- SOLAR SYSTEM-ASTEROIDS, COMETS, METEORS,METEORITES

ASTEROIDS

Asteroids are rocky bodies, which revolve round the Sun in the big gap of about 550 million kms between orbits of Mars & Jupiter.
There have been countless references to them as "space debris" or "vermin of the skies". Otherwise they are overlooked as they are small, dull, inert and lack an atmosphere. However, for the last three or four thousand million years asteroids have been the most important agent of surface modification on a great many bodies including Mercury and our very own Moon.
There are over 8000 large asteroids, and many more which are too small to detect easily. Only 26 asteroids are known to have a diameter greater than 200 kilometers, and it is likely that all asteroids above 100 kilometers in size have been detected. However, not many of the smaller asteroids have been discovered - there may be over a million asteroids with a size of 1 kilometer.
The largest asteroid is 1 Ceres with a diameter of 974 kilometers. This one asteroid contains about a quarter of the mass of all the asteroids. In terms of size, Ceres is followed by 2 Pallas, 4 Vesta and 10 Hygiea. These asteroids are between 400 and 538 kilometers in diameter. All other known asteroids are less than 350 kilometers across.
Found in all shapes & sizes – rotate on their axis every 5 to 20 hrs depending on their sizes.
2 main groups – Trojan asteroids in the orbit of Jupiter &
Chiron asteroids between Saturn and Uranus .

What are asteroids?
Asteroids are rocky bodies, which revolve round the Sun in the big gap of about 550 million kms between orbits of Mars & Jupiter.
________ largest asteroid.
Ceres

50,000 asteroids between jupiter and mars. They also revolve around sun and sometimes they crash in to others and fall into other planets. Doesn’t fallin earth due to atmosphere which burns the asteroids before it lands into the earth.


COMETS

Among the most brilliant, and most rare objects in the night sky. These soaring beacons with their beautiful tails come from the outer realms of the Solar System.

What are comets?

Comets are very small bodies consisting of frozen gases and grains of dust and rock. It is when comets approach the inner Solar System and become subjected to the Sun's heat, that they develop a tail millions of kilometers long and thus become very large objects.
Comets have head called coma and a long tail.Their size range from a few hundred meters to a few hundred kilometers in diameter.

It takes them hudreds and sometimes even thousand of years to complete one revolution around the sun.
When their path passes ear Sun, we are able to see them.
Their tails are turned away from the sun.
Many comets do not have tails.
Appear as small luminary objects moving across sky.

TWO KINDS OF COMETS:-

1.PERIODICAL COMETS: have regular orbits round the sun and occur at fixed intervals.
Halley’s comet – due next in 2062
Seen at interval of 76 years.

2. NON PERIOICAL COMETS:
Seen very rarely and not sighted at regular intervals
Comets are visible only when they travel close to the sun.
Ice melts and gas and dust are swept back to form the tail.
Tail always points away from the sun.

SATELLITES

They are small bodies which rotate on their axes & revolve round the planets.
Satellite = a follower and they follow the planets in their paths round the Sun.
They are opaque bodies like the planets and shine by reflecting the sunlight falling on them. All planets do not have satellites .

METEORS

They are small planetary particles, which are attracted by Earth’s gravitational force when they pass near the Earth.
They are seen as rapidly moving bright objects in the sky lasting for a few seconds.
They are known as shooting stars.
Millions of such meteor-like particles are found scattered in space.
When they enter the Earth’s atmosphere, they get burnt due to friction and appear as bright objects.

image showing meteor of Leonid Meteor shower taken from space

METEORITES

Some meteors are of large size.
Only a part of their mass gets burnt. The remaining mass falls on the Earth as a large boulder.These are called meteorites .

Some of these meteorites are quite large and weigh more than 50 tonnes.
Their impact on earth’s surface has resulted in the formation of craters

TERMS TO REMEMBER:

Star : A self-luminous ball of gas

Planet : A rocky or gaseous mass that revolves round a star.

Satellite : A body that revolves round a planet.

Galaxy : Large cluster of stars.

Asteroids :Small rocky bodies

Meteorite : a large rocky body entering the earth's atmosphere.

Terrestrial : Earth-like.