Resources: Worksheet

Terminology: Spiral GalaxiesEllipticalsIrregularsBarred SpiralsDwarf GalaxiesLenticular Galaxies

Demonstrations: Rotational VelocityDensity WaveLookback TimeEffects of GravityScale of the Universe

Astronomers classify galaxies by shape, color, star formation rate, mass, luminosity, black hole activity, and more. Today we will focus on classifying galaxies by shape and color.

There are many classification of galaxies. The three primary shapes of galaxies are spiralsellipticals, and irregulars. Spiral galaxies have discernible structure (e.g., spiral arms) and can be more disk like. Elliptical galaxies do not have structure and usually look like balls of stars and dust. Irregular galaxies are galaxies that don't fit within either of these categories.

As you will learn in this lab, there are many subclassifications. For example, there are barred spirals  like the Milky Way, and non barred spiral galaxies. Similarly, the compactness an elliptical galaxy is important to its classification. The size of the galaxy can determine what type it is as well, such as small elliptical galaxies are called dwarf galaxies.

Atlas of the Universe: 100 Million light years from the Sun. Credit: Richard Powell

Learning Goals: Students will learn about morphology of galaxies and classify different types of galaxies.