1. A star is light years away from the earth. what does it mean ?

2. Why do stars look ery small although these are huge heaenly bodies ?

3. The moon is not a star but still shines . give reason

4. The planet mercury does not have an atmosphere. How does this affect the temperature on its surface ?

5. Write two uses of remote sensing satellites ?

6. Why does planets not collide with each other during their journey around the sun ?

7. Why does the tail of a comet always point away from the sun ?

8. Why does the pole star appears stationary in the sky, where as all other stars appears to move from East to West.

1) A star is some light away from earth is the distance from earth to that particular star.

One light year is the distance travelled by light through vacuum, in one year. It is used to measure the distance between stars or galaxies.

4)  Mercury has very extreme temperature changes. During the Day mercury gets up to 10 ten times more solar energy than Earth. So temperatures can go as high 430 degrees Celsius. That is 806 degrees Fahrenheit. Because the planet has no atmosphere to retain that heat, night time temperatures on the surface can drop to -280 degrees Fahrenheit (-170 degrees Celsius).

6) As they move in well defined orbits and because the gravitational pull from the sun and other planets keep the planets going in a circular motion and not bumping into each other.
The planets each have defined Elliptical, not circular, orbits that remain constant because of gravitational pull of the sun and from each other.

7) Comets tails always point away from the sun because the gas and dust melted off of the comet is pushed back by the solar wind, a stream of particles that flows away from the sun. Since the solar wind always flows away from the sun, it always pushes the stuff melted from the comet away from the sun, forming the tail.

rest all the parts are well answered by your friends and for more refernce you can refer to the study material provided.