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What is a Galaxy?

Geography | 7-14 yrs | Reading Pod, Interactive

What are Galaxies?

Galaxies are sprawling space systems composed of dust, gas, and countless stars.

Galaxies consists of a large number of star systems, clusters and interstellar clouds.

It is believed that galaxies were formed due to a big cosmic bang billions of years ago. Just few milliseconds after the massive explosion took place the clouds of gases began to collapse and compress under the gravity, forming galaxies.

Nearly all stars belong to a group of galaxies.

Different Shapes of Galaxies

We have galaxies of different shapes. The most common shape is the elliptical galaxy, then we have the disk shaped galaxy called the spiral galaxy and finally the galaxies with an unusual or irregular shape called irregular galaxies. Galaxies which consist of less than a billion stars are considered as small galaxies.

1. Spiral Galaxies

The most beautiful type of galaxies are Spiral Galaxies. Its spiral arms are circling waves which form new stars. This shaped galaxy consists of a flat disk with a bulge in the center and spiral arms. This flat shape disk includes stars, planets, gases and dust particles which revolve around its center. It appears like a cosmic pinwheel.

For example :- Our Milky Way

2. Elliptical Galaxies

As the name suggests this shape is generally round but is stretched longer along one axis than the other. They consist of around one trillion stars but very little dust. These stars are generally older or evolved stars. In elliptical galaxies the stars orbit in random directions along a common center. The largest known galaxies are of this shape.

For example :- Maffei 1

3. Irregular Galaxies

Galaxies which are not spiral or elliptical are known as irregular galaxies. These galaxies seem to have no shape and lack distinct form. This is because they fall under the gravitational influence of close by galaxies.

For example :- Sextans A

What Galaxy is the Earth located in?

We are part of the spiral galaxy called Milky Way. It contains our Solar System. The name Milky Way has been derived from its appearance. It appears like a “milky” glowing band across the night sky. The naked eye cannot distinguish individual stars. It is called the Milky way because they say on a clear night it looks like milk spread across the sky. The Milky way consists of about 200 billion stars including our Sun.

Our galaxy is spiral in shape and has three main components :-

  • A disk in which our solar system exists
  • A central bulges
  • A halo

Galaxies often crash into one another. Even our own galaxy has had others pass right through it.

Don’t worry though, galaxies can pass through each other quite safely. Stars are so far apart that the chances of them colliding is very unlikely.

There are two galaxies close to our galaxy, the Andromeda and the Triangulum, both of which are Spiral galaxies.