Ellipticals- Elliptical galaxies' names are pretty self-explanatory. They are named as such because they are in elliptical shapes much like a football. The stars in elliptical galaxies are evenly spread out in every which way unlike spiral galaxies. Elliptical galaxies are often a shade of red due to the old and cool stars that these galaxies contain. Elliptical galaxies are the largest galaxies of all and can sometimes contain trillions of stars.
Spiral- You will know if a galaxy is a spiral galaxy if you see a flat disk of stars around it and a bright nuclei in the center. Spiral arms form as a result of density waves. As the density waves compress the interstellar gas new stars are born. These new born stars are what makes the spiral arms bright. To get a better idea of what spiral galaxies are you are living in one right now, the Milky Way.
Irregulars- Galaxies classify under "irregular" if they are neither elliptical or spiral. These are the smallest galaxies of all and sometimes have as little as one million stars. There are some smaller irregular galaxies that orbit the Milky Way, too. Lastly, some scientists believe that irregular galaxies acted as a sort of building blocks at one point in time to create the larger galaxies.
Spiral- You will know if a galaxy is a spiral galaxy if you see a flat disk of stars around it and a bright nuclei in the center. Spiral arms form as a result of density waves. As the density waves compress the interstellar gas new stars are born. These new born stars are what makes the spiral arms bright. To get a better idea of what spiral galaxies are you are living in one right now, the Milky Way.
Irregulars- Galaxies classify under "irregular" if they are neither elliptical or spiral. These are the smallest galaxies of all and sometimes have as little as one million stars. There are some smaller irregular galaxies that orbit the Milky Way, too. Lastly, some scientists believe that irregular galaxies acted as a sort of building blocks at one point in time to create the larger galaxies.
"Galaxies." SDSS SkyServer DR7. N.p., n.d. Web. 14 Feb. 2011.
<http://cas.sdss.org/dr4/en/astro/galaxies/galaxies.asp>.
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