What defines a dwarf galaxy?

A dwarf galaxy is characterized primarily by its small size and relatively low luminosity, typically containing a few billion stars or fewer. These galaxies are significantly smaller than regular galaxies, such as spiral or elliptical galaxies, which can contain hundreds of billions to trillions of stars.

Dwarf galaxies often exhibit various features that set them apart, such as being irregular in shape and having a lower gravitational influence, which means they often reside within the gravitational pull of larger galaxies. Their relatively low star count contributes to their classification, with many dwarf galaxies being home to star formation and exhibiting a mix of old and young stars.

In contrast to the other descriptions, a large galaxy with multiple superclusters refers to large-scale structures that encompass many galaxies, while a galaxy composed of billions of stars would typically be classified as a normal galaxy rather than a dwarf. Additionally, a galaxy with no stars at all would not fit the definition of a galaxy, as they are fundamentally collections of stars, gas, dust, and possibly dark matter. Thus, the defining feature of a dwarf galaxy is indeed its status as a small galaxy, often with just a few billion stars.