Star Systems and Galaxies

Star SystemsMany stars come in different types of groups.

Star system = Group of 2 or more stars

• Double Stars: 2 stars held together by gravity (Binary Stars)

• Triple Stars: 3 Stars

• Eclipsing Binary: Binary Star - when one star passes in

moves front of the other.

Finding Binary Stars and Planets

• Many planets and companion stars are too small to be seen. We can detect them by the “wobble” that the visible star has.

Star Clusters

• Open Cluster: Loosely organized star group of about 1000 stars.

• Globular Cluster:

Large grouping of older stars

Densely packed and more than

a million stars.

Galaxies

• Very large groups of Stars, dust and gas• Most stars are found in Galaxies• A typical Galaxy has over 100 billion Stars!!!!!!

Types of Galaxies

• Spiral: Shaped like a pinwheel Our galaxy, the Milky Way, is a Spiral

Elliptical Galaxy

• Ball shaped – lens shaped• Very little dust and gas• Contains older stars

Irregular Galaxy

• Do not have regular shapes

• Usually smaller – a lot of dust and gas

Quasars

• Very bright, but very distance objects.• Many are more than 10 billion light years

away. (At the edge of our known Universe)

Moving Galaxies and the “Big Bang” Theory

1. We have proof that galaxies are moving away from each other. Doppler Shift - Red Shift

2. If galaxies are moving away, then they were closer together at some point in time.

3. Big Bang Theory: All matter was concentrated at one point some - 15 billion years ago – exploded outward forming Galaxies, Stars and planets

Our Local Group of Galaxies

Milky Way Andromeda

2 million light years

Local Group: Galaxies that are closest to the Milky Way

( about 20 Galaxies)