How Big Is The Galaxy?

All the stars in the universe are not scattered around randomly but instead are grouped together in clusters called Galaxies.

Galaxies come in many shapes and sizes and contain billions of stars. It is said that there are more stars in the universe than there are grains of sand on every beach in the world.

Our Solar system of the Sun and planets live in a galaxy very similar to this one. We are placed about three quarters of the way out from the center of our Galaxy.

We call our galaxy the Milky Way. On a very dark night the Milky Way can be seen stretching across the sky.

So, how big is it?

It is so big that we cannot measure it in miles or kilometers, the numbers would be mind boggling. Instead we must use another measurement called a light year.

What is a light year?

If you switch a light on, the light leaves its source and arrives at your eyes instantaneously.

Now if you stood 186 thousand miles away or about 2 thirds the distance to the Moon and the light was switched on it would take 1 second for the light to reach you.

Are you good at Mathematics?

Right, well multiply 186 thousand by 60 seconds. That comes to 11 million miles. If you stood this far away it would now take 1 minute for the light to reach you.

Multiply this by 60 minutes and it would now take 1 hour for the light to reach you. Multiply this by 24 hours and it now takes 1 whole day to reach you. Over 160 Billion miles.

Now the hard bit, multiply this number by 365, the number of days in a year and this massive number is, 1 light year.

Our Galaxy is 100 thousand light years across. A ridiculous number to try to understand.

Let's put it another way if you travelled at 186 thousand miles per second it would take you 100 thousand years to get from one edge to the other.

Okay, still too big a number. Let's try and make it more understandable.

If the Sun was a ball 1 meter across then the Earth would be a garden pea over 100 meters away. And Pluto would be a grain of rice 4 km or one light day from the Sun.

On this scale, the nearest star Alpha Centuri which is 4 light years away or 26 Trillion miles would be on the Moon.

There are only seven stars less than 10 light years from Earth.

The nearest Galaxy to ours is called the Andromeda galaxy it is an incredible 2.2 million light years away. That means we are seeing it as it was 2.2 million years ago.

So without Captain Kirk and his star ship's warp speed it looks like we'll be staying close to home for a long time to come.