Types Of Galaxies

By Alessandro R.

What is a Galaxy?

Galaxies are large collections of dust, gas, and stars that can contain several million to trillions of stars. They can also range in size from a couple of thousand to several hundred thousand light-years.

3 Main types of Galaxies

Elliptical Galaxies

Elliptical galaxies look like elliptical, or oval, shaped disks. They often are sized like a sphere or elongated sphere. They have a smooth light that emits from their center that grows fainter the farther you go from the center. They are classified by how elliptical they are, the bigger the number, the more elliptical it is. This range varies from 0 to 7 aka E0 to E7, E is put in front to show that they are elliptical galaxies.

Spiral Galaxies

Spiral galaxies contain three main aspects about them, they all have a bulge, disk, and halo. The bulge can be found in the middle of the galaxy, it contains mainly older stars. The disk is made mainly of dust, gas, and young stars. The disks are what make up the spirals of the galaxy. The halo is a globular structure located around the bulge and parts of the disk. They are classified based on how tight their arms are.

Irregular Galaxies

Irregular galaxies have no true structure and are mainly just clusters of stars. They are only divided into 2 groups Irr I and Irr II. Irr II stars mainly contain humongous quantities of dust which blocks a lot of the light from the stars. Irr I are composed of elemental hydrogen gas and young hot stars.

Works Cited

Gordon, K. SPACE PHOTOS THIS WEEK: Spiral Galaxies, Wildfire, More. Digital image. Http://news.nationalgeographic.com/news/2009/02/photogalleries/week-in-space-pictures-29/images/primary/090210-01-spiral-galaxy-hubble_big.jpg. 10 Feb. 2009. Web.

NASA. Irregular Galaxy. Digital image. Http://phillips.seti.org/kids/galaxies.html. Web.


"Ask an Astronomer." Cool Cosmos. Caltech, n.d. Web. 02 June 2015.


Milky Way Galaxy. Digital image. Http://upload.wikimedia.org/wikipedia/commons/thumb/4/43/ESO-VLT-Laser-phot-33a-07.jpg/300px-ESO-VLT-Laser-phot-33a-07.jpg. Web.


Elliptical Galaxy. Digital image. Http://frigg.physastro.mnsu.edu/~eskridge/astr101/m87outer.gif. Web.


"Types and Classification of Galaxies." CLASSIFICATION. Cornell, 18 Apr. 2000. Web. 2 June 2015 <http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm>