An elliptical galaxy surrounded by faint arcs or shells of stars, lying at right angles to its major axis. One to twenty shells may be seen, nearly concentric but incomplete. They are ‘interleaved’ in such a way that successive shells usually occur on opposite sides of the galaxy. About 10% of bright ellipticals show shells, most of them in regions of low density of galaxies. No spirals are known with such shell structure. Shell galaxies may be the result of a giant elliptical digesting a low-mass companion galaxy.
Subjects: Astronomy and Astrophysics.