How do galaxies form?

Looking at Galaxies

When you look up at the night sky especially in summer you'll see a faint line of stars. This is our galaxy.

A galaxy is a really big operation of stars, made of gas (mostly), hydrogen, dust, and dark matter that circles around a common center that is bound by gravity. People have called galaxies "island universes."

Big Bang

When astronomers look at some of the farthest parts of the universe with a powerful telescope they see a bunch of galaxies. Galaxies got there first start from the Big Bang close to 14 billion years back.

Following the Big Bang, the primordial universe (the first formed universe) was consisted of radiation and super duper small particles.

We do not know exactly how galaxies got here but we have some ideas and theories about how they formed and took the many shapes and sizes we see today.

We know they are very old and were formed at the beginning of the universe. Astronomers realized the two main types of galaxies are elliptical and spiral.

The different types of galaxies were originally described by Edwin Hubble in the 1960's.

Elliptical Galaxies

An elliptic galaxy is a galaxy having a shape like an oval and a bright profile. Elliptical galaxies have a faint rounded shape with no visible bright star or spiral pattern.

Most elliptical galaxies are made of older, small mass stars. They can tend to be surrounded by large numbers of globular clusters.

Elliptic galaxies are believed to make up 10-15% of the galaxies in the Virgo Super cluster, but are not the main type of galaxy in the universe overall.

Spiral Galaxies

When two galaxies float too close to one another they may form a spiral galaxy. Spiral galaxies look like balls with arms.

A spiral galaxy has a center part and then one or more arms that swirl out from the center part. The center part of a spiral galaxy is made up of old stars and black holes.

Most spiral galaxies have more than two arms. Our galaxy is called the Milky Way and it is a spiral galaxy.

There is lots of hot gas and dust in the arms of a spiral. This is where new stars are formed. The gas and hot dust in the arms is used to make new stars.