A galaxy is a giant group of stars and space objects rotating in the universe. A galaxy can contain up to billions of stars like our Sun.
They can be so large it can take billions of years to travel across them with a spaceship. Even if we were traveling at the speed of light, it would take thousands of years for us to go from one end to another.
Galaxies contain every space object you can think of. Planets, comets, moons, dust, and even dark matter.
Galaxy Image, Hubble Telescope
Nearly every large galaxy has a black hole at the center. That is because gravity is very powerful there.
A Black Hole, Illustration
How many galaxies are there?
Scientists think there are more than 100 billion galaxies in the universe. If you think this is a lot, you are right! If you started counting right now, you would reach 1 billion after 60 years!
What kind of galaxies are there?
There are three main types of galaxies. Elliptical, spiral and irregular.
Our Home, The Milky Way Galaxy
Our galaxy is only one of those 100 billion galaxies. It is called the Milky Way because it looks like a milky road in the sky. If you travel to somewhere really dark at night you can see it with your own eyes.
Milky Way at Night
In fact, the word “galaxy” comes from the Greek word for milk, “gala”.
So let’s come back to our galaxy The Milky Way. Scientists think it looks like this from the outside.
The Milky Way Galaxy
We can’t really take a picture of it. It would take millions of years to exit the Milky Way and take a real picture. Instead, we use computer simulations to guess how it looks. But don’t worry, the real one looks very similar to this.
Can you guess how many stars there are in The Milky Way? Scientists think there are more than 150 billion stars in our galaxy. Can you imagine! Our Sun is only one of those stars!
Where is our planet in the Galaxy?
We are a little far from the center thankfully. We wouldn’t want to be close to the supermassive black hole in the middle of our galaxy.
Our Place in the Galaxy
Our Solar System floats around close to the inner parts of the Orion Arm. We spin around the galaxy at about 220 kilometers per second.
How old is our galaxy?
The Milky Way is very, very old. It formed 13.51 billion years ago, just after the beginning of the Universe. Our planet the Earth is only 4.5 billion years old. So our galaxy is three times older than our planet.
A Galactic Year
As we can see in the picture, The Milky Way is a spiral type galaxy. It constantly spins around at 550 kilometers per second. We can’t feel this on Earth because we are spinning along.
In 250 million years, we will have rotated our galaxy. This is called a galactic year. 1 galactic year ago, Earth was ruled by dinosaurs.
Our planet one galactic year ago
Our Neighbour The Andromeda Galaxy
The infamous Andromeda Galaxy is 2.5 million light-years away from our Solar System. It is a galaxy very similar to ours. It is around the same size and is also a spiral galaxy.
The Andromeda Galaxy
The amazing fact is that The Andromeda Galaxy and The Milk Way Galaxy are on a collision course. They will merge in 4.5 billion years. That will be a sight to behold.
Largest Galaxy in the Universe
The largest galaxy scientists ever found is called IC 1011. Our galaxy looks really tiny if you compare them. It is 6 million light-years wide, compared to Milky Way’s tiny 100,000 light-years.
IC 1011 Galaxy
Can we travel to other galaxies?
Not yet. And unfortunately, we probably won’t be able to for a very long time. The nearest galaxy to our Solar System is 25,000 light-years away. So maybe we should consider other, more modest travel destinations, like Mars, which only takes 6 months to get to.