There are an estimated 170 billion galaxies in the universe. Galaxies consist of stars, gas, dust, and dark matter that are gravitationally bound together. There are three main types of galaxies: spiral galaxies which have a bulge, disk, and halo structure; elliptical galaxies which are elongated spheres; and irregular galaxies which have no defined shape. Galaxies are further classified based on their structure.

1. H. Taylor

2. What is a galaxy?
A galaxy is a massive, gravitationally bound system consisting
of stars, stellar remnants, an interstellar medium of gas and dust, and dark
matter

3. How many are there?
Estimated that there are 170 billion different galaxies
Space in between galaxies is known as “intergalactic space”

4. Type and Classification
There are 3 main types of galaxies, though subtypes are not uncommon
1.
Spiral galaxies
2.
Elliptical galaxies
3.
Irregular galaxies

5. Spiral galaxies
3 main components
1.
Bulge
2.
Disk
3.
Halo

7. Elliptical galaxies
Shaped like an elongated sphere
Sometimes look almost football shaped
Classified based on elongation from a perfect circle
• Scale from E0 to E7

9. Irregular galaxies
Have no set structure
Divided into two groups:
1.
Irr I
2.
Irr II

11. Works Cited
http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/galaxytypes.htm
http://ircamera.as.arizona.edu/NatSci102/NatSci102/text/spiraltypes.htm
http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm
http://www.dailymail.co.uk/sciencetech/article-2016050/Incredible-images-taken-amateur-astronomer-Georgiy-Suturin-usingcamera-home-telescope.html
http://en.wikipedia.org/wiki/Galaxy
http://www.bobthealien.co.uk/galdiff.htm
http://www.spacetelescope.org/images/opo9941a/
http://www.microcosmologist.com/blog/wp-content/uploads/2012/07/Mass-Effect-3-Galaxy-mass-relays-exploding.jpg
http://www.dailygalaxy.com/my_weblog/2011/03/new-discovery-evolution-of-the-most-massive-galaxies-in-the-universe.html
http://galaxiez.weebly.com/types-of-galaxies.html
http://abyss.uoregon.edu/~js/ast123/lectures/lec11.html
http://annesastronomynews.com/photo-gallery-ii/galaxies-clusters/the-bird-eso-593-ig-008-is-a-triple-merger-of-galaxiescomposed-of-one-barred-spiral-one-more-irregular-and-a-third-the-head-irregular-galaxy-that-seems-to-be-forming-stars-at-afrantic-rate-65/
http://kids.britannica.com/comptons/art-90852/The-Cigar-galaxy-is-classified-as-an-irregular-galaxy
http://pmhsscience9110.wikispaces.com/Galaxies
http://spore.wikia.com/wiki/File:Spiral-galaxy-wallpaper.jpg