galaxies beyond the milky way. types of galaxies there are three main types of galaxies: 1.spiral...
Post on 03-Jan-2016
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Galaxies
Beyond the Milky Way
Types of GalaxiesThere are Three main types
of Galaxies:
1. Spiral (like the Milky Way)
2. Elliptical (Round without internal Structure)
3. Irregular (No structure at all, usually small)
Spiral Galaxies have a structure similar to the Milky Way.
There are two subtypesTypical (S type)Have multiple arms
Barred Spirals (SB type)With only two arms that are
often partially straight
Spiral Galaxies vary from:
Tight arms and a big bulge(Like the Sa type below)
ToLoose arms and a small bulge
(like the Sd type above)
Ellipticals
Ellliptical vary in shape from more spherical (E0) to very flattened (E7) , to disk-like (S0)
Other differences between galaxy types
Spiral Galaxies tend to be
• Of about the same size• Full of interstellar dust
and gas• Composed of both
younger (population 1) and Older (popualtion 2) stars
Elliptical Galaxies • Vary significantly in size• have less interstellar
gas and dust.• Have only older (pop 2)
starsPerhaps because they lack
the gas and dust needed to form new stars
Hubble’s “Tuning Fork”
Hubble thought that galaxies started as elliptical (E0) and changed into S types evolving into Spiral S types and then into an Irregular (Irr) type…
we no longer believe that is so.
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