The Hubble tuning fork is a very generic tool used by astronomers to try and identify a category for galaxies. Although often considered too simple to properly categorize most galaxies, the tuning fork does allow astronomers to get off to a start when discovering new galaxies.
Ellipticals
Ellipticals are some of the oldest and brightest galaxies. They are categorized by how much shape they have. On a scale from 0 to 7, the higher the number, the more elliptical the galaxy is. An E0 galaxy is essentially circular.
Lenticulars
Lenticulars are a less specific than spirals and ellipticals and act as a transition phase. Most lenticulars look like a hazy central bulge surrounded by an elliptical cloud.
Spirals
Spiral galaxies are the most common galaxies in the universe. There are two types of Spiral galaxies, normal spirals and barred spirals. Each category is defined by level a, b, and c where the later the letter, the less tightly wrapped the spiral is. A level spirals are also brighter than b and c spirals. Barred spirals, as expected, have a bar structure that goes through the center and the galaxies are usually a bit more elongated than standard spirals.
Work used:
http://www.astro.cornell.edu/academics/courses/astro201/galaxies/images/m87_ell.gif
http://freestarcharts.com/images/Articles/Messier/M86_NASA_AURA_STScI.jpg
http://cas.sdss.org/dr6/en/proj/basic/galaxies/images/ellipt3.jpg
http://bama.ua.edu/~rbuta/nearirs0/plate014c.jpg
http://www.noao.edu/image_gallery/images/d4/m81y.jpg
http://www2.lowell.edu/rsch/LMI/gallery/n6946_2.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Hubble2005-01-barred-spiral-galaxy-NGC1300.jpg/350px-Hubble2005-01-barred-spiral-galaxy-NGC1300.jpg
http://wind.caspercollege.edu/~marquard/astronomy/images/ngc1365_vlt.jpg
https://www.noao.edu/image_gallery/images/d4/m109a.jpg
http://scienceblogs.com/startswithabang/files/2010/09/File-Ngc253-2mass-barred-spiral.jpeg
http://jtgnew.sjrdesign.net/images/galaxies_elliptical_ngc1132_hst.jpg
Good job Simon! 5/5
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