Galaxies

Spiral Galaxies These are made up of parts including the disk, bulge, and arms. Spiral arms contain gas, dust, and stars. The arms rotate around the center of the galaxy.

Spiral Galaxy The bulge is the center of the galaxy. Arms rotate around the bulge. Most of the stars and dust are located here. The disk is the entire galaxy, including all of its arms.

The Disk

Barred Spiral Galaxies Same shape and composition as a spiral galaxy. Have its arms connected or linked by a bar.

Elliptical Galaxies Shaped like spheres or eggs. Have minimal dust and gas between the stars. Stars are mostly old. Smaller than spiral.

Irregular Galaxies Faint galaxies. Have no definite shape. Smallest galaxies. Have few stars. Not common.

The Center of the Galaxy Most galaxies, we predict, have a supermassive black hole at their center. These holes are millions or billions times greater than the sun. These are invisible; we have to infer that they are there. Black holes pull in gas from nearby stars and give off very bright light. This bright light is called a quasar, which means seeming like a star.

Our Home – The Milky Way The sun and all of our planets are part of this galaxy. We are on the edge of our galaxy. Why is it named this? Our galaxy appears hazy or milky in appearance because of its many stars. Astronomers measure the distance between planets in astronomical units of AU It is a spiral galaxy. It is more than 100,000 light years in diameter. The bulge, or the area with most of the stars, is 26,000 light years from the sun.

The Milky Way