What is a lenticular (S0) galaxy? A galaxy with a disk and central bulge like a spiral galaxy, but with no spiral arms A galaxy with a smooth brightness profile, lacking the central bulge and disk of a spiral galaxy A spiral galaxy with fuzzy and poorly formed spiral arms A galaxy with a lot of gas and dust and no particular structure

A galaxy with a disk and central bulge like a spiral galaxy, but with no spiral arms

Explanation:

A Lenticular galaxy is a kind of galaxy intermediate between elliptical galaxy and a spiral galaxy in the Morphological classification system of galaxies. They have a central bulge or disc just like a Spiral galaxy but lacks the arms of spiral galaxy. If looked edge on they appear to be spiral and if looked face on they appear to be elliptical.

The absence of spiral arms can be attributed to the absence of star formation. They mainly consists of ageing stars.