In the Hubble Sequence, what classification is given to a galaxy that is labelled S0?

In the Hubble Sequence, a galaxy classified as S0 is known as a lenticular galaxy. This classification is significant because lenticular galaxies exhibit characteristics of both spiral and elliptical galaxies. They have a prominent disk structure similar to spiral galaxies but lack the well-defined spiral arms. Instead, they often have a smooth, rounded appearance like elliptical galaxies, and they can contain a bulge at their center.

Lenticular galaxies are typically thought to represent an intermediate stage of galaxy evolution. They suggest a transition, where a galaxy has depleted its gas reservoir, leading to reduced star formation, thus resulting in a more uniform structure. This classification plays an important role in understanding the diversity of galaxy morphologies and their evolutionary paths within the broader context of galactic formation and behavior.