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Dwarf PlanetS

Pluto, Ceres and Eris are called dwarf
planets because their sizes are much
smaller than a normal planet. They also
revolve around the sun in their fixed orbit.
Pluto was earlier considered as a planet,
but its size is so small that now it is Pluto Ceres Eris
considered as a dwarf planet.

3. SaTelliTeS

Satellites are the smaller celestial bodies which revolve around their planets. The word
satellite means an atterdasrt or a companion. Like planets, satellites also have no light or
heat of their own. Our Earth has only one natural satellite—The Moon. Find out the number
of satellites of other planets. Which planet has the largest number of satellites?

Human made satellite : It is an artificial body. It is
designed by scientists to get information about the Atmosphere cannot exist on the moon
Universe or for communication. It is carried by a because escape velocity of moon is 1.86
rocket and placed in the orbit around the Earth. m/s whereas escape velocity of gases is
2.63 m/s. Gases cannot stay there.
Some of the Indian satellites in space are INSAT,

IRS, EDUSAT, etc.

Moon

The moon moves around the earth in about 27 days and 8 hours. It takes exactly the same
time to complete single rotation. As a result, only one side of the moon is visible to us on
the earth. Although this cycle is a continuous process, there are eight distinct, traditionally
recognised stages (phases).

Thus the changes from New Moon to Full Moon and back again are called the phases of the Moon.
1. New Moon : The moon is not visible because the illuminated side of the moon faces
away from the earth. It is a New Moon night or Amavasya.

2. Waxing Crescent : The moon appears to be partly, but less than one-half illuminated
by direct sunlight.
3. First Quarter : One-half of the moon appears to be illuminated by direct sunlight.

4. Waxing Gibbous : The moon appears to be more than one-half, but not fully illuminated
by direct sunlight.

5. Full Moon : The moon appears to be completely illuminated by direct sunlight because
the illuminated side of the moon faces the earth. It is Full Moon night or Poornima.
6. Waning Gibbous : The moon appears to be more than one-half, but not fully illuminated
by direct sunlight.

7. Last Quarter : One-half of the moon appears to be illuminated by direct sunlight.

8 Social Studies-6