NGC 253 (Sculptor Galaxy) is an intermediate spiral galaxy in the constellation, Sculptor.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.
Spiral galaxies are named by their spiral structures that extend from the center into the galactic disc. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disc because of the young, hot OB stars that inhabit them.
Spiral Galaxies originate from Edwin Hubble's work on a system classify galaxies, the Hubble sequence. The Hubble sequence is the most commonly used system for classifying galaxies, both in professional astronomical research and in amateur astronomy. It has been around since 1926. Edwin Hubble's work in general was revolutionary in understand our understanding of the universe and our place within it.
Barred Spiral Galaxy[]
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about half of all spiral galaxies. Bars generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. Our own galaxy is an example of a spiral galaxy
Edwin Hubble classified spiral galaxies of this type as "SB" (spiral, barred) in his Hubble sequence and arranged them into sub-categories based on how open the arms of the spiral are. SBa types feature tightly bound arms, while SBc types are at the other extreme and have loosely bound arms. SBb-type galaxies lie in between the two. SB0 is a barred lenticular galaxy. A new type, SBm, was subsequently created to describe somewhat irregular barred spirals, such as the Magellanic Clouds, which were once classified as irregular galaxies, but have since been found to contain barred spiral structures. Among other types in Hubble's classifications for the galaxies are the elliptical galaxy and irregular galaxy
Some examples of Spiral Galaxies are:
- Milky Way
- Andromeda Galaxy
- Triangulum Galaxy
- M63 (Sunflower Galaxy)
- M81 (Bode's Galaxy)