What is a galaxy?
The scientific definition of a galaxy is a “gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.” In simple terms, this means a large clump of things that you might find in space.
The differece between a galaxy and the universe
One of the most common misunderstandings about galaxies is the difference between a galaxy and the universe.
Here is how you can tell them apart:
First, the universe is everything. Every atom, every star, every black hole, every galaxy is in the universe. Galaxies are groups of matter within the universe.
Second, there is only one universe we know of. When someone says “our” universe, they mean the one and only universe that we know of. However, there are many galaxies that we know of. So when someone says “our” galaxy, they mean the Milky Way and not another galaxy like the Andromeda galaxy.
Classification of galaxies
There are three ways: shape color, and activity.
Shape refers to how it looks: elliptical, spiral, barred spiral, or irregular
Color is what color the Galaxy is — this tells us generally what type of star is in that galaxy.
Activity tells us how many new stars are forming: high means that many stars are forming, medium means that the galaxy just stopped producing stars, and dead means that the galaxy stopped producing stars a long time ago. To learn more about stars, click here: https://theastroenthusiast.com/all-about-stars/.
How you can get involved
Classifying galaxies is very hard for computers to do, but very easy for humans. Luckily, there is a site where you can help: Galaxy Zoo. If you have some free time, head over to this website, as classifying galaxies is a great help to researchers.
Do you have any cool facts about galaxies? Let me know in the comment below!
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