The tail of the comet is always directed away from the Sun. The tail will be longest in the position B because the tail is visible only when the comet passes through the inner solar system and B is nearest.

Difference between a natural and an artificial satellite.

Applications of artificial satellites are
(i) These kinds of satellites are used for weather for casting such as rainfall, snowfall, etc.
(ii) For communication purpose such as long distance transmission of telephone calls, TV programmes, internet the artificial satellites are used.
(iii) The natural sources of earth are usually surveyed by the artificial satellites.

Since, the planets are celestial bodies which revolve around the Sun. They do not have their own light due to which they reflect Sun's light. Out of eight planets of solar system, only five are clearly visible to the naked eye. Planets keep changing slightly during the day or after the night with respect to the stars. Difference between stars and planets are

(a) Constellation
(b) Great Bear or Ursa Major
(c) Pole star

(a) We will see the full moon on the left side (according to figure) in the evening.
(b) On the right side lower part, we will see the crescent moon which is on the next day of the new moon day.

We know that (time period)2  ∝ (radius of orbit)3
\({ T }_{ 1 }^{ 2 }={ Kr }_{ 1 }^{ 3 }\)                     . . . (i)
\({ T }_{ 1 }^{ 2 }={ Kr }_{ 2 }^{ 3 }\Rightarrow { T }_{ 2 }^{ 2 }=\left( \frac { { r }_{ 1 } }{ 2 } \right) ^{ 3 }\)          .... (ii) \(\left[ \because { r }_{ 2 }=\frac { { r }_{ 1 } }{ { r }_{ 2 } } \right] \)
\(\frac { { T }_{ 1 }^{ 2 } }{ { T }_{ 2 }^{ 2 } } =\frac { { r }_{ 1 }^{ 3 } }{ { r }_{ 1 }^{ 3 } } \times 8\)
⇒ \({ T }_{ 2 }^{ 2 }=\frac { { T }_{ 1 }^{ 2 } }{ 8 } \)
⇒ \({ T }_{ 2 }=\frac { 1 }{ 2\sqrt { 2 } } \)
It means that time period reduces by \(\left( \frac { 1 }{ 2\sqrt { 2 } } \right) \) factor.
So, the days in a year will be approx. 129 instead of 365 days.

(i) Constellations
(ii) Ursa Major
(iii) Remote sensing
(iv) Akash Ganga

There are eight planets in our solar system:
(i) Mercury (Budh) : It is nearest to the Sun. It is the smallest planet of our solar system. It is very difficult to visualize because it is near to the Sun. It has no satellite.
(ii) Venus (Shukra) : It is nearest to the Earth. It is the brightest planet. It is also called as morning and evening star due to its appearance. It also has no moon or satellite. It rotates from East to West.
(iii) Earth (Prithvi) : The earth is the only planet where life exists. It has special environmental conditions, right distance from the Sun, so has right temperature, presence of water and blanket of ozone that makes life possible here.
(iv) Mars (Mangal) : It is the first planet outside the orbit of the Earth. It appears reddish, so is called red planet. It has two small natural satellites.
(v) Jupiter (Brihaspati) : It is the largest planet. It rotates very rapidly on its axis. It has large number of satellites. It also has faint rings and large moons.
(vi) Saturn (Shani) : Saturn is yellowish in colour. It has beautiful rings. It has large number of satellites. It is least dense, density is less than water.
(vii) Uranus and Neptune: They are outermost planets of our solar system. Uranus rotates East to West, and has high rotation speed

Stars are present both during day time as well as during night time. Because of the bright light of the Sun, the stars are not visible during day time.

(i) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
(ii) Earth is the planet on which the life is known to exist.
(ill) Students of Ramesh seem to be very sharp minded and intelligent. They learn all the facts immediately which Ramesh teaches them.