In astronomy,  we study about the composition, behaviour of universe and its celestial bodies like stars, planets, moon, asteroids, etc.

It consists of mostly hydrogen at very high temperature. At this temperature, the hydrogen atoms fuse slowly and get converted into helium by releasing the large amount of energy and heat.

'Phobos' is a natural satellite of the planet 'Mars'. Actually Mars has two natural satellites or the moons known as Phobos and Deibos.

Alpha Centauri is the nearest star to our solar system. It is about 4.3 light years away from us.

Alpha Centauri is the nearest star to our solar system. It is 4.3 light years away from us. As we know that there exists a huge temperature on the star and this breaks the atoms into electron and ions. This combination of ions and electrons is known as plasma, the fourth state of matter. It is plasma which gives the stars, the glowing effect.  

Sirius is the brightest star in the sky. It is located very close to the hunter shaped constellation Orion.

Mercury is an inferior planet. Inferior planet is one whose orbit is smaller than that of the Earth. Mercury is the closest planet to the Sun and the smallest of our solar system. As its orbit of translation is less than that of the Earth, it is an inferior planet of this solar system.

The Venus is considered as the God of love and beauty. It is the second closest planet to the Sun and the sixth largest of the solar system. Here, life is not possible because it is very hot.

Mercury is the nearest planet to the Sun. It is the smallest planet of the solar system. It has no satellite. Its average temperature is about 350⁰C. 

It is consisted of five dominating stars which resembles like a Letter W of English Alphabet. It is seen in the month of October in the nothern part of the sky.

Light Year is defined as the distance travelled by light in a year. 1 light year = 365 X 24 X 60 X 60 X 3 X 10⁸                        = 9.46 x 10¹⁵ m

The Earth is at an optimum distance from the Sun. Therefore, it is neither too hot nor too cold. The average temperature of this planet is nearly 15⁰C,  which is suitable for the existence of life. 

Mercury is very near to the Sun and its period of revolution around the Sun is 88 days,  which is minimum among all the existing planets of our solar system. 

Jupiter mainly consists of hydrogen and helium. Its outer cloudy region contains methane in gaseous form and ammonia in crystalline form. The presence of carbon dioxide is negligible.

When the size of a meteors is very large, then they do not get burnt completely in the air of the atmosphere  and reach the surface of the earth. Such heavenly bodies are called as meteorites. The largest meteorites ever found on the Earth is in Namibia. It weighs nearly 60 metric tones. The polar region of Antarctica is the place where we find the meteorites in abundance. 

Jupiter is the largest of all the planets of our solar system. Its mass is nearly twice as compared to the combined mass of all other planets. It is so large that about 1300 Earth can be accomodated in this giant planet. It is composed of 90% hydrogen,10% helium with small traces of methane, water and ammonia. It is just too small to be called as a star. It rotates very quickly around its axis. Its period of rotation is 9.55 hours. 

Asteroids are the groups of small bodies which are made up of rock and metal. They revolve around the Sun in a belt between the Mars and the Jupiter. They are also known as minor planets.

Venus is composed mostly of carbon dioxide. There are thick layers of clouds of sulphuric acid, which produce green house effect to raise its surface temperature to 460⁰C. Actually, it is hotter than Mercury despite being nearly twice as far from the Sun. 

The planet,  which lies outside the orbit of Mars is called Jovian planet because of their similarity of structure with that of Jupiter. This planet consists of gases like hydrogen and helium. Actually, it is a gaseous planet having low density, have a large number of satellites and have rings around them. 

Neptune is the eighth planet from the sun. It is known as the God of the sea. It is 4500 x 10⁶ km away from the Sun.

Moon is a satellite of Earth. It does not have light of its own. It just reflects a part of light of the Sun falling on it. Next to Sun, it is the brightest of all other celestial objects. 

It is known as the sister of the Earth. It is mostly composed of carbon dioxide. On Venus, the Sun rises in the west and sets in the east. It has no satellite.  

It has the most number of satellites. It has nearly 60 natural satellites, discovered so far. 

Venus is a female planet because it is called as Goddess of love and beauty.  

 Mars is red in colour this is why it is known as Red Planet.