What are galaxies?

What is a galaxy?

A galaxy is a massive group of hundreds and millions of stars and other objects, all held together with gravity and orbiting around a common center.

milky way is he galaxy in which our solar system exists .

All stars are visible to the naked eye from earth also belongs to the Milky way . Our sun is just a star in millions of the other.

There are billions of galaxies in the universe .Some of  galaxies are smalls having a millions of stars and some are Huge having as many as 500 Billion of stars or even more.

Why is the Milky way special to us?

Milky way is the galaxy in which our sun earth and other planets exists.

Milky way is a huge whirl pool like galaxy that rtates once every 200 million years.It is made up of at least 100 billion of years as wall as dust and gas.It is so big that light at the speed of 3000000000 km per hour takes about 100000 years to cross from one side to other.

Scientists think that the center of the galaxy contains a super massive black hole which is named as Sagittarius A* That swallows up anything that passes too close.The sun and its planets,including our earth lies in a quiet part of the Milky way which is about half of the way from the center.

Are all galaxies of same type?

No not all galaxies look alike . There are three different types of galaxies That are 

1. Spiral galaxies.

2.Elliptical galaxies.

3.Irregular galaxies.

Our neighbours(courious fact)

Through there are billions of galaxies in the univers , only three of them can be seen from earth by a telescope.Andromeda is one of the closest or the closest galaxy, which is about 2.2 million light years away.

How are galaxies born?

Scientists believe that clumps of gas joined together to form young galaxies called Protogalaxies.

These protogalaxies are formed in different ways.Some have huge clumps of gas at the center which formed many massive explosions . Massive explosion forced out the gas out of the galaxy.So , only the star formed of gas remained. Protogalaxies formed in this sway become elliptical galaxies.

Some times , a protogalaxy contain only small clumps of gas.Since its center, since its center is smaller so there will be less  big explosions.Most os the gas is retained along with the star that have formed,and the galaxy becomes a spiral galaxy.

Irregular galaxies are probably protogalaxies in which explosion are still going on.

This is all about galaxies .