The two Magellanic Clouds are examples of irregular ones, while Andromeda is a spiral one.
One type of these entities has structures that should break down upon rotation, a dilemma known as the "winding problem," which can be resolved using density wave theory. Blazars and quasars are two examples of the "active nuclei" of these structures, another example of which is found in their "Seyfert" variant. Their types are shown on the Hubble Tuning Fork diagram. The two Magellanic Clouds are examples of irregular ones, while Andromeda is a spiral one. For 10 points, name these systems of astronomical objects, a spiral one of which is the Milky Way.
One type of these entities has structures that should break down upon rotation, a dilemma known as the "winding problem," which can be resolved using density wave theory.
galaxies [accept word forms; accept spiral galaxies until “Magellanic”]