Hubble sequence

The Hubble sequence is a way of organizing different types of galaxies based on their shapes and features.

Imagine you have a bunch of toys that are all different shapes and sizes. You could sort them into groups based on their shapes - all the round ones in one group, all the long ones in another group, and so on. That's kind of what the Hubble sequence does with galaxies!

There are three main types of galaxies in the Hubble sequence: elliptical, spiral, and irregular.

Elliptical galaxies are round or oval-shaped, like a circle or an egg. They don't have the arms and disks that spiral galaxies do, and they don't have a lot of new stars being born. They tend to be made up of older stars.

Spiral galaxies, on the other hand, have a distinctive spiral shape. They have a big disk of stars and gas in the middle, with spiral arms that curve outward. Spiral galaxies are where most of the new stars in the universe are formed.

Irregular galaxies are a bit harder to describe, because they don't have a specific shape or pattern. They can be a mix of spiral and elliptical features, or they can be chaotic and messy-looking.

Galaxies are also classified by smaller details, like the number of spiral arms they have or the size of their nucleus (the center of the galaxy). Scientists use these details to subdivide the three main types of galaxies even further.

So, the Hubble sequence is basically a way for scientists to sort different types of galaxies into groups based on their shapes and features, like sorting toys into groups by their shapes.