Lenticular galaxy

A galaxy with a prominent central bulge and disk but little interstellar gas or ongoing star formation. Its smooth appearance lies between that of spiral and elliptical galaxies.

Galaxy morphology: The study and classification of galaxies by their shapes and visible structures. Lenticular galaxies occupy a distinct class in the system that organizes galaxy shapes.
Ram-pressure stripping: The removal of a galaxy’s gas by pressure exerted as it moves through hot surrounding gas. It can deprive a disk galaxy of gas needed to sustain star formation.
Spiral galaxy: A disk galaxy with spiral arms, typically containing gas, dust, and ongoing star formation. It shares a disk with lenticular galaxies but usually retains visible arms and more active star formation.
NGC 1023: A nearby barred lenticular galaxy in the constellation Perseus. Its prominent bar and disk illustrate the structural variety within the lenticular class.
Galactic bulge: A dense, roughly spheroidal concentration of stars at a galaxy’s center. The central bulge is one of the defining structural components of a lenticular galaxy.
Galaxy harassment: Repeated high-speed encounters and tidal forces that alter galaxies in dense environments. These encounters can transform disk structure and help suppress star formation.
Elliptical galaxy: A galaxy with a smooth, ellipsoidal stellar distribution and little cold gas or ongoing star formation. It resembles a lenticular galaxy in smoothness but lacks a prominent disk.
NGC 3115: A nearby edge-on lenticular galaxy in the constellation Sextans. Its edge-on view makes the flattened disk and central bulge especially apparent.
Galactic disk: A flattened, rotating component of stars, gas, and dust in a galaxy. Its disk distinguishes lenticular galaxies structurally from most elliptical galaxies.
Strangulation (astronomy): The loss or cutoff of a galaxy’s supply of fresh gas, causing star formation to fade as existing gas is used up. A slow decline in star formation can leave a disk galaxy with a lenticular appearance.

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