Types of Galaxies
A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. A galaxy is held together by gravity. Some scientists think there could be as many as one hundred billion galaxies in the universe. Galaxies have different shapes and are classified according to the Hubble classification.
There are four main classifications of galaxies
Elliptical which is featureless and spiracle.
Spiral galaxies have arms that spiral outward.
Lenticular galaxies are given the symbol S0. These galaxies consist of a bright central bulge, similar in appearance to an elliptical galaxy, surrounded by an extended, disk-like structure.
Irregular galaxies are any other galaxy.
Elliptical galaxies are classified with an E and are further classified as from E0 to E7.
E0 are the most spherical and E7 are the most elongated.
Spiral galaxies are also subdivided into two main types, regular which are classified with a S and barred spirals classified with a SB. A barred spiral galaxy has a bar shape in the center.
Our milky way galaxy is a barred shaped Galaxy.
The regular spiral galaxies are subdivided according to how tight the arms are, SA arms are tightly wrapped and SC have arms that are lose.
Barred galaxies are also subdivided, SBa have tightly woven arms SBc have lose arms.
Irregular galaxies and Lenticular Galaxies are not subdivided.
Irregular are grouped with an Irr and Lenticular Galaxies are classified with a SO.
0 comments:
Post a Comment