Galaxy

Ever wondered where we live? I know you have come across this question many times. We live in Earth, our Earth and many planets are in the Solar system and the Solar System lies in a galaxy known as Milky Way Galaxy. Now the question arises, what is a GALAXY? Let's know about it...

 What is a Galaxy?

A galaxy is a huge group of dust, gas, billion of stars and solar systems all held by gravitational force. It also comprises of nebula, asteroids, comets, dark matter and black holes. The universe comprises of more than trillions of galaxies. A galaxy is like a particle of sand in a huge beach.

Until 1920 we only knew about our galaxy, The Milky Way. At this time people were confused about a fuzzy spiral shape in the space. Guesses were that it was a nebula or other galaxy, there was a big debate about this. Ultimately, Henrietta Swan Leavitt proved that the large spiral shape in the sky was a galaxy near to our Milky Way Galaxy and named it Andromeda Galaxy.

Henrietta Swan Leavitt

How Galaxies were formed?

After the formation of the universe, hydrogen and helium were roaming all around, it also contained dust and dark matter. As the time passed many changes were occurring in universe, one of this change was the formation of the stars from the gases present. After 100 billion years of the formation of the universe, because of gravity these stars, dust and dark matter started coming near and formed star clusters. As the time passed all these stars merged together to form a disc, which we call Galaxy.

Types of Galaxies

Basically there are three main types of Galaxies. They are-

Spiral Galaxies: A Spiral galaxy has a thin disk of stars rotating around a galactic center. It has two or more spiral arms existing outwards. These spiral arms contain a majority of stars in the galaxy. The best example of Spiral galaxy is our Milky Way Galaxy, another example is our nearest galaxy Andromeda.

Spiral Galaxy

Elliptical Galaxies: This type galaxies are mostly found in the universe. These galaxies are smooth and doesn't have any distinct features as spiral galaxies. Mainly these galaxies are formed when a small galaxy gets submerged with a large galaxy. Example: Cygnus A, M87

Elliptical Galaxy

Irregular Galaxies: As the name suggests these galaxies do not have any perfect shape. Neither these are classified as spiral galaxy nor elliptical. Basically, they are formed when two galaxies collide with each other. Example: Large and small Magellanic clouds.

Irregular galaxy