Star Systems & Galaxies

Star Systems & Clusters Most stars are members of groups of two or more stars, called star systems. Our solar system only has one star.

Binary Stars Star systems with two stars are called binary stars. A eclipsing binary system occurs when one star periodically blocks the light from another star. Binary stars eclipsing binary system

Star Clusters Many stars belong to larger groupings called star clusters. Open clusters have a loose chaotic appearance and are made up of young stars (less than a billion years old). Globular clusters are round and densely packed groupings containing older stars (12-13 billion years old). PLIEADES OPEN CLUSTER 47 Tucanae, 10-12 billion years old, 15,000 light-years from Earth. Globular Cluster

Galaxies Galaxies are large groups of stars, star systems, star clusters, dust, and gas bound together by gravity. Come in a variety of shapes and sizes. Contain trillions of stars. Classified by shape. It is estimated that there is over 100 billion galaxies.

Three Shapes of Galaxies Andromeda spiral galaxy Spiral Galaxies Flattened arms that spin around the center, mostly made up of young stars. Elliptical Galaxies round, from flat disks to spheres, contain older stars. Irregular Galaxies Irregular shape, so they make up their own category, generally young stars with lots of dust and gases. Elliptical Galaxy M87 Irregular Galaxy M82

Milky Way Galaxy Our solar system is located in a spiral galaxy called the Milky Way.

Scale of the Universe Since numbers astronomers use are often very large, they use scientific notation to describe sizes and distances in the universe. Example: 1 light-year is 9,500,000,000,000,000 meters or 9.5 X 1015 meters.

Galaxies, and the Universe

The Universe The Universe is made up of many Galaxies. The study of the origin, structure, and future of the Universe is called Cosmology. Astronomers use galaxies far away to hypothesize how they form.

Doppler Effect Change in wavelength caused by the apparent motion of the source. Blue Shift - light from objects coming toward you is compressed looks more blue. Red Shift - light from objects moving away looks more red.

Big Surprise No Galaxies showed blue shift All galaxies showed red shift. Which means All galaxies were moving away The universe is expanding

Origin of the Universe The theory that the universe began with a tremendous explosion is known as the Big Bang Theory. 13.7 billion years ago, all matter was compressed into one spot and expanded rapidly. Explained red shift.