The Formation of Galaxies

1. The Formation of Galaxies By: Zakeyia Cherelle Bacon

3. Origin of Galaxies How do galaxies form in the first place? To answer this question, astronomers must travel back in time, exploring the early universe by observing objects that are extremely far away in space. Because it takes time for light to travel through space, looking through a telescope is like looking back through to time. The farther one looks, the further back one travels. It helps us better understand about how our galaxy became to be.

4. The Big Bang The Big Bang is one of the theories why we have galaxies today. The Big Bang theory states that the universe began with a tremendous explosion. According to the theory, about 12-15 years ago, all the contents of the universe were gathered together under extreme pressure, temperature, and density in a very tiny spot. For some reason unknown to mankind, it rapidly expanded. Some of the expanding energy turned into matter that eventually became as the galaxies we know of today.

5. Galaxies Galaxies are large groupings of stars in space. Galaxies come in a variety of sizes and shapes. The largest galaxies contain more than a trillion stars. Some of the smaller ones have only a few million. Astronomers don’t count the stars because of the immensity of them, they only estimate from the size and brightness of the galaxy how many sun-sized stars the galaxy might have.

6. Spiral Galaxies Spiral Galaxies- a galaxy with a bulge in the center and very distinctive spiral arms. Some characteristics about this galaxy are: • The disk is a region of star formation and has a great deal of gas and dust. • Huge collections of billions of stars, most of which are flattened into a disk shape, with a bright, spherical bulge of stars at its center.

7. Elliptical Galaxies Elliptical galaxies- have very bright centers and very little dust and gas. Because there is so little gas, there are no new stars forming, and therefore elliptical galaxies contain only old stars. There are two categories of elliptical galaxies: • Giant elliptical galaxies- huge elliptical galaxies • Dwarf elliptical galaxies-smaller elliptical galaxies

8. Irregular Galaxies Irregular galaxies are galaxies that don't fit into any other class. As their name suggest, their shape is irregular. They are also close companions of large spiral galaxies, whose gravity may be distorting the shape of their smaller neighbors. Some facts about the irregular galaxy are: • Their shape is uncommon • Collectively they are thought to make up about a quarter of all galaxies

9. Contents of the Galaxies Galaxies are composed of more than just stars. There are larger features within the galaxies that are made up of stars or the material of stars. Among these are: • Gas clouds • Globular Clusters • Open Clusters

10. Nebula The Latin word for “cloud” is nebula. Nebulas are giant clouds of gas and dust. Some types of nebulas glow by themselves, while others absorb light and hide stars. Some nebulas are regions where new stars form. Spiral galaxies generally contain nebulas, but elliptical don’t. They are also known to produce breathtaking images.

11. Globular Clouds Globular Cluster are groups of older stars. A globular looks like a ball of stars. They have up to 20,000 to 100,000 stars in an average globular cluster. They are located in a spherical halo that surrounds a spiral galaxies such as the Milky Way. Globular clusters are also common around giant elliptical galaxies.

12. Open Clusters Open clusters are groups of stars that are usually located along the spiral disk of a galaxy. Newly found open clusters have many bright blue stars. There may be a few hundred to a few thousands stars in an open clusters. They are also visible even without a telescope.