Stars and the Solar System
1-Sundial -A Clock based on shadows of an object due to Sunlight .
2-Celestial Bodies -The heavenly bodies are known as celestial bodies.
3-Local noon -The time when the shortest shadow occurs is called the local noon time at that place.
4-Dakshinayanam – When the Sun looks like travelling towards south of the sky, it is called Dakshinayanam.
5-Uttarayanam -When the Sun looks like travelling towards north of the sky , it is called Uttarayanam
6-Artificial satellites -The man made satellites which revolving around the planets are called Artificial satellites
7-Asteroids -There is large gap in between the orbits of Mars and Jupiters.This gap is occupied by large number of small objects that revolve around the Sun.These are called Asteroids.
8-Comets-Comets are also members of our Solar system.They revolve around the Sun in elliptical orbit.
9-Meteors- Meteors are known as shooting stars.A meteor is usually a small object that occasionally enters the earth surface.
10-Meteorite -The body that reaches the earth is called a meteorite.Meteorites help scientists in investigating the nature of material from which solar system was formed.
11-Planets – The Planets look like stars but they do not have light of their own.
12-Satellites-Any celestial body revolving around another celestial body is called its satellite.
13-Pole Star -Stars do not remain in the same spot in the sky but revolve around the pole star.The Pole star however remains fixed at one place.
14-Galaxy-A galaxy is an extremely large group of stars and planets that extends over many billions of light years.
15-Constellation -A constellation is a group of stars which form a pattern and have a name.
16-Phases of the moon-The sunrays fall on the moon illuminate half of its surface in all the position.However, we can not see the entire illuminated surface from the earth in all the position.So we can see phases of moon.
17-On the new moon day,sun and moon are on the same side of the earth.
18-On the full moon day,sun and moon are on either sides of the earth.
19-The length of the tail of the comet grows in size as it approaches the Sun.
20-Artificial satellites are revolving at a height of 38,000 km from the surface of the earth and 44,300 km from the centre of the earth.
21-The time period of the artificial satellite in stationary orbit is 24 hours.
22-Aryabhatta was the first Indian artificial satellite.
23-Every planet revolve round the sun in an elliptical orbits.
24-The astronomical distances are measured by using a unit light year.
25-The distance travelled by the light in one year is called light year.
25-The highest unit for astronomical distances measured is par-sec.( par-sec = 3.26 light years)