Huge Nebula

Jupiter

Andromeda

Venus

Jupiter

Mercury and Venus

Venus

Comets

The group of galaxies of which our Milky Way is a part is called 'Local Group'.

Comets are made of frozen matter and dust particles.

The planet Uranus appears as if it is rolling along its orbit.

Jupiter is a stormy planet.

The Pole Star is the best example of a variable type of star.

Wrong-,. Mercury is the planet closest to the Sun.

Wrong-. Jupiter is called a stormy planet.

Right- Jupiter is the biggest planet.

• Mars is the fourth planet in our solar system.
• Planet Mars is that it is red in colour. This is due to the presence of iron in its soil. Hence it is also known as the red planet.
• The highest and largest mountain in our solar system called Olympus Mons is present on the planet Mars.
• Mars has two satellites. Its rotation is in about 24 hours and it takes about 1.88 years to revolve around the sun.

Various types of galaxies which are identified according to their shapes are:

• Spiral galaxy: These are the spiral structures that extend from the centre into the disc.
• Elliptical galaxy: These galaxies have nearly ellipsoidal shape which consists of stars, gas and dust.
• Irregular galaxies: These galaxies don’t have a distinct regular shape.
• Barred spiral galaxies: These are spiral galaxies with a central bar-shaped structure composed of stars.

• A galaxy includes innumerable stars and their planetary systems.
• It has many celestial bodies such as clusters of stars, nebulae, clouds of gases, clouds of dust, dead stars, newly born stars, etc.
• The Milky Way is our galaxy in which our solar system is included. It has planets, satellites, asteroids, dwarf planets and meteors.

There is a great variety in stars. Some are very bright, some are faint. There are many colours among the stars. e.g. Blue, white, yellow and reddish. Some stars have varying brightness. Their luminance changes constantly.

The different types of stars in the universe are stated below:
Sun-like Stars: These are particularly similar to the Sun in size but there is a lot of variation in terms of temperature.
Red Giants: The temperature of these stars ranges between 3000°C and 4000°C. But their luminance can be 100 times that of the sun.

Super Nova: They are larger and even brighter as compared to the red giant stars and even the Sun.

Binary or Twin Stars: A pair of two stars in which one revolves around the other or they both revolve around a common centre is known as binary or twin stars. 
Variable Stars: These stars have a variable shape and brightness i.e it keeps on changing whenever they expand or contract. Example is Pole Star.

Comets arc of two types :(1) Long period comets (2) Short period comets

This classification is based on the time taken by them to make an complete revolution around the sun.

• Long Period Comets: These comets complete one revolution around the Sun in 200 and more years. Great Comet of 1843 is one of the examples of this type.
• Short Period Comets: These comets complete one revolution around the Sun in years less than 200. One of the examples is Halley's comet that takes 76 years to complete the revolution. It last appeared in 1985

Meteors: These are rocky pieces originating from the asteroid belt and enter the Earth’s atmosphere as a result of its gravitational pull. On entering the Earth’s atmosphere, they acquire very high speeds. These high speeds of meteors cause friction with the Earth’s atmosphere and thus the meteors heat up and evaporate completely. Meteors are also known as shooting stars.

Meteorites: These are the unburnt part of meteors which fall to the surface of Earth on occasions when the meteors do not burn completely in the atmosphere itself.

• Neptune is the eighth planet of our solar system.
• One season on the Neptune planet lasts for about 41 years.
• The winds blow at a very high speed on Neptune.
• Neptune has 13 satellites. It takes approximately 16 hours and 11 minutes to rotate around itself and 164 years for one revolution around the sun.