Galaxies are classed according to what?

Galaxies are classed according to their shape, which can be spiral, elliptical, or irregular.

Galaxies are classed according to their shape, size, and other structural features. The most common classification system for galaxies is the Hubble sequence, also known as the Hubble tuning fork diagram, which categorizes galaxies into three main types: elliptical galaxies, spiral galaxies, and irregular galaxies. These classifications are based primarily on the visual appearance of galaxies as observed from Earth. Elliptical galaxies are shaped like ellipsoids and lack distinct spiral arms, while spiral galaxies have a central bulge and spiral arms extending from the center. Irregular galaxies do not have a regular shape and often exhibit chaotic features. Additionally, galaxies can be further classified based on their size, luminosity, color, and other properties observed through telescopic observations and scientific analysis.