Q.6: What is Oort Cloud?
Ans: It is a reservoir of comets outside the solar system.

Q.7: What is the difference between a star and a planet?
Ans: Star is self-luminous heavenly body while planet is rocky-luminous body. Planets, however reflect ligth.

Q.8: What are auroras?
Ans: These are Northern Polar lights which are caused by electrified particles send out by the Sun. These charged particles from the sun cascade down into the Earth's upper air. Being charged, they are attracted to the magnetic poles, which is why auroras are best seen from higher latitudes. They are particularly common around the peak of the sunspot cycle. This phenomenon occurs in the atmosphere about 65 miles above sea level.

Q.9: Why does a total Solar Eclipse can happen only at the time of the new Moon?
Ans: A total Solar Eclipse a situation when the bright surface of the Sun is fully covered by the Moon can happen only at the new Moon, when the Earth, Moon and Sun are lined up with the Moon between the other two, its night-side turned towards us.

Q.10: Why do we see but only one face of the Moon always?
Ans: Because, the period of rotation of the Moon is equal to its period of revolution around the Earth. It is also called the synchronous rotation of the Moon which keeps the same face towards the Earth.