![]() Sometimes the faint remnants of spiral arms can be seen. Im class galaxies are the most common and show just a hint of structure. Irregular galaxies are divided into two classes, Im and IO. These galaxies have no discernible shape or structure. Irregular Galaxy - A fourth type of galaxy is known as the irregular galaxy. E0 galaxies nearly circular in shape while E7 galaxies are extremely elongated or stretched out. Elliptical galaxies are represented by the letter E and are divided into seven subgroups according to their shape. Unlike spiral galaxies, they have no bright nucleus at their center. Our own Milky Way galaxy is now believed to be a barred spiral galaxy.Įlliptical Galaxy - Elliptical galaxies vary in shape from completely round to extremely elongated ovals. SBa galaxies have a short bar of stars extending from the center while SBc galaxies have a long, well-defined bar. These subgroups are labeled SBa, SBb, and SBc. Barred spiral galaxies are represented by the letters SB and are arranges into three subgroups according to the openness of the arms. About one third of all spiral galaxies are barred spiral in shape. The arms spiral out from a straight bar of stars instead of from the center. Sa galaxies have spiral arms that are wound tightly around the nucleus while the arms of Sc galaxies are wound much more loosely.īarred Spiral Galaxy - A barred spiral galaxy is very similar to a spiral with one important difference. S0 galaxies have a bright nucleus but have no spiral arms. Spiral galaxies are represented by the letter S and are divided into four subgroups. Spiral Galaxy - Spiral galaxies are characterized by a distinct flattened spiral disk with a bright center called the nucleus. Today, galaxies are divided into four main groups: spiral, barred spiral, elliptical, and irregular. It divides galaxies into three main classes with a few variations. This classification system is known as the Hubble Sequence. ![]() After studying galaxies for many years, astronomer Edwin Hubble decided to classify galaxies according to their shape. In fact, all of the galaxies in the universe seem to be moving away from each other at tremendous speeds. The stars within the Milky Way revolve around the central core. And just like our solar system, our galaxy is in motion. All of the stars we see in the night sky are part of the Milky Way. Our solar system is located about 3/4 of the way out from the center in one of the galaxy's spiral arms. The Milky Way is a gigantic spiral disk with a bright, central bulge. Our Sun is only one of over 100 billion stars in a galaxy called the Milky Way. ![]() Our own solar system is located within a galaxy. Since most of the space between galaxies is thought to be empty, a galaxy is essentially an oasis in space. Many probably even contain large amounts of unseen dark matter. They contain stars, planets, moons, comets, asteroids, nebulae, dust, neutron stars, and black holes. Most of the objects we know of in space are contained within galaxies. Galaxies are defined as large groupings of stars, dust, and gas held together by gravity.
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