GAL - Types of Galaxies LESSON
Types of Galaxies
A galaxy is a system of stars, gas, and dust held together by gravitational attraction. Our solar system is located in the Milky Way Galaxy. It is thought that this is a spiral galaxy that has relatively loose wound arms. However, astronomers have begun to suspect that it actually is a barred spiral galaxy starting back in the 1990's. Our Sun is located on one of the outer "arms" of the Milky Way, closer to the outer portion of the galaxy than the center of it.
| Galaxy Name | Example | Picture | Description |
|---|---|---|---|
| Spiral Galaxies | Messier 81 Galaxy |
These galaxies are shaped like large flattened disks that spin around a central super-massive nucleus. Many of them are divided loosely into spiral arms, but a small percentage have no such structures and just appear to be featureless disks. |
|
| Barred Spiral Galaxies | Messier 83 Galaxy |
These are similar to standard spiral galaxies, except that the spiral arms emanate from a large central column, or bar, that straddles the galactic core. |
|
| Elliptical Galaxies | M82 Galaxy (Starburst Galaxy) |
They have no discernible central core, and they appear to be ellipsoid, or spherical, in overall shape. |
|
| Irregular Galaxies | NGC 1427A Galaxy |
These appear in many chaotic shapes and have little to no overall internal structure. |
While the chart above gives you a generic classification of galaxies, the Hubble Space Telescope has enabled astronomers to further group or classify galaxies. Below is the Hubble Classification of Galaxies. It is also referred to as the "Tuning Fork" Diagram because of its shape. It organizes galaxies into Elliptical, Spiral, and Barred Spiral.
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