- “Blue dwarfs” refers to the young stars and “Red giants” to the old stars.
- When the hydrogen of a star is depleted its outer regions swell and redden. This stage of star is called “Red Giant”.
- The orbits of planets around the sun or of satellites around the earth can be ‘Circular’ and ‘Elliptic’.
- A terrestrial planet is planet of ‘A dense, rockery body’.
- The term “Syzygy” is referred to when the moon, sun and earth lie along a straight line.
- When the earth is at the maximum distance from the sun, it is called ‘Aphelion’.
- Due to elliptical path, distance of the earth from sun keeps changing. It is nearest to sun on 3rd January known as ‘Perhelion’.
- Sometimes the moon passes between the sun and the earth, this phenomenon is known as ‘Solar eclipse’.
- Sometimes the earth passes exactly between the moon and the sun, this condition is known as ‘Lunar eclipse’.
- ‘Lunar eclipse’ is caused when the earth comes between the sun and the moon.