Astronomy Notes: Information On Galaxies

An explanation of the Milky Way as well as a guide to different galaxy types that have been observed in the universe.

We live in a galaxy called the Milky Way. But what is this galaxy made of? How did it form? Read this article to learn about the types and nature of galaxies.

Galaxies are huge groups of stars, gas, dust and space materials. These groups form when gas, dust and stars are pulled together by a magnetic core. Galaxies actually rotate, which is why sometimes one can see the outline of the Milky Way in the sky.

Our galaxy, the Milky way, is a spiral galaxy. Not all galaxies are like ours, however, There are four major types of galaxies: spiral, barred spiral, elliptical and irregular.



Elliptical Galaxies

Elliptical galaxies have a spherical or elliptic shape, and maintain this shape as they move through space. They contain groups of old stars, and little bits of gas and dust. Some elliptical galaxies resemble nebula, or large clouds of gas, because they are so old. These galaxies are especially valuable, because their stars may have been created around the time of the Big Bang.

Irregular Galaxies

Irregular galaxies are stuck in a galactic tug-of-war between other galaxies. They are often composed of very young stars, and contain a lot of gas and dust. Their irregular shape can take any forms, and some irregular galaxies even resemble spiral and elliptical! It is possible for these galaxies, out of contact with other galaxies, to become spiral or elliptical galaxies, although this is rare. Sometimes irregular galaxies are called "starburst galaxies" because their dust and gas is a huge breeding ground for new stars to form. Certain galaxies are formed when two galaxies collide. These collisions are called "radio galaxies" because of the intense radio signals that they send into space.

Spiral Galaxies

These galaxies have a bulge in their center, surrounded by a spiraling of galaxy. The spiral part of these galaxies is referred to as "arms." These galaxies contain much gas and dust, usually spread out along their arms. Inside this dust and gas, new stars form. Spiral galaxies, like all other galaxies, rotate. Their rotation can be measured by careful scientific mapping.

Barred Spiral Galaxies

These galaxies are spiral galaxies, but with a bar-like bulge in the center. Certain elliptical galaxies contain hints of a bar and spiral, leading researchers to believe that they were once barred spiral galaxies.

When galaxies become "dead," or they contain dead stars, known as "brown dwarfs," and lots of dust and gas, they are sometimes called "dwarf galaxies." Our sightings in the far universe show that these galaxies tend to be on the moving edge of the Big Bang. Dead galaxies may sometimes turn into a nebula when all stars die.

It is possible to galaxies to clump together and form "clusters." Our galaxy is part of another group of about twelve galaxies. Some clusters contain thousands of galaxies, and these clusters are sometimes visible in the night sky.

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