A small, low-luminosity galaxy. Dwarf ellipticals (dE) and dwarf irregulars (dIrr) are probably just fainter examples of this general type of galaxy but dwarf spheroidals are a separate type. Dwarfs in general are the most common galaxies in the Universe. There are no dwarf spirals, since no spirals are known with an absolute blue magnitude below −17 (about 109 solar luminosities).
Subjects: Astronomy and Astrophysics.