Types of galaxies
Galaxies are massive collections of stars, and astronomers classify them into distinct types based on their appearance and shape. The most famous classification system is the Hubble sequence, devised by Edwin Hubble in 1926, which divides galaxies into three main categories. Elliptical galaxies have smooth, featureless appearances ranging from nearly circular to highly elongated shapes. Spiral galaxies feature a flat disk with stars arranged in spiral arms and a bright central bulge. Lenticular galaxies are intermediate between the other two types, with a bulge and disk but without visible spiral structure. A smaller category, irregular galaxies, lack any regular structure. Understanding galaxy types matters because it helps astronomers study how galaxies form, evolve, and interact with one another across cosmic time.
Sources
- en.wikipedia.org: “Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance, shape, structure, and distribution of light.”
- en.wikipedia.org: “Elliptical galaxies have smooth, featureless light distributions and appear as ellipses in images.”
- en.wikipedia.org: “Spiral galaxies consist of a flattened disk, with stars forming a (usually two-armed) spiral structure, and a central concentration of stars known as the bulge, which is similar in appearance to an elliptical galaxy.”
- en.wikipedia.org: “These broad classes can be extended to enable finer distinctions of appearance and to encompass other types of galaxies, such as irregular galaxies, which have no obvious regular structure (either disk-like or ellipsoidal).”