- Eclipse: In our Solar system every celestial body receives light from the Sun. On the Earth two types of eclipses are observed, solar eclipse and Lunar eclipse.
- Solar Eclipse:
- When the moon comes in between the sun and the earth, it obstructs light from the sun and cast shadow on the earth. This is called solar eclipse.
- It may be total or partial solar eclipse. Solar eclipse occurs during new moon position.
- Size of moon compared with sun is very small solar eclipse doesn’t last for longer period. It lasts for an average time of 2 ½ minutes.
- Lunar Eclipse:
- It occurs when the earth comes in between sun and moon.
- Earth obstructs the light of sun and cast shadow on moon and hence lunar eclipse occurs.
- It occurs during full moon position. Lunar eclipse may be partial or total, it depends upon the position of the moon during eclipse.
- Since the size of the earth is bigger than moon, so a lunar eclipse may occur up to two hours.
- In a year there is a possibility of maximum seven eclipses in a calendar year which includes both lunar and solar eclipse. And there would be minimum four eclipses – two lunar and two solar in a year.
- This is because the orbital plane of moon around the earth is inclined to 5 degree from the earth’s orbital plane around the sun.
- When new moon and full moon position occurs due to inclination of moon orbit it always moves ahead little bit and misses eclipse. That’s why every new moon or full moon doesn’t have eclipses.
- Due to the small size of the moon a ring solar eclipse is possible however a ring lunar eclipse is never possible.
- Solar eclipse can be seen only at a certain place of the earth. However lunar eclipse can be seen at any place of night side of the earth. This is because in solar eclipse the path of totality is maximum 275 km.
- Pole Star: It is also called as North Star and it indicates the north direction. It always remains in the same position in the sky. It lies in the north close to the axis of rotation of the earth. In ancient times people uses pole star in determining direction during night. One can locate pole star in the sky with the help of constellation Saptarishi.
- Constellations: In a clear night sky we can observe that various group of stars forms a recognisable pattern or shape. This recognisable pattern or shape formed by group of stars is called constellations. Since the position of stars in the constellations is fixed, ancient people conceived these constellations to recognise stars in the night sky. Let’s discuss some constellations.
- Ursa Major: It is found in the Northern Hemisphere. It is named after bear. Ursa Major is also known by the name of Great Bear and Big Dipper. Ursa Major is not visible from southern hemisphere of the earth except few points. It can be seen in summer times. Ursa Minor is a part of the Ursa Major which can be clearly seen in the photo.
- Ursa Minor: It is the part of the Ursa Major. It contains seven stars and is also known by the name of Small Bear, Saptarishi and Little Dipper. It also a northern hemisphere constellations and in the southern hemisphere it is visible only from few points. Saptarishi is useful in locating the Pole Star and hence North Direction. It can be seen during summer times. See in the figure.
- Orion: It can be seen in the winter nights. It represents a hunter. It can be seen in both the hemisphere in a clear night. With the help of Orion we can locate the brightest star of the sky known as Sirius or called as Dog Star. See the figure.
- Cassiopeia: it is the constellation which looks like a distorted shape of letter W or M.
- Leo Major: It can be seen in northern hemisphere in spring season. It represents lion and is a Zodiac constellation. It can be located in the night sky with the help of its two brightest star i.e., Regulus and Alpha Leones.