1. Characteristics Of Stars
Galaxy: A collection of stars, gases and dust.
Universe: Contains billions of
galaxies.

2. Types of Galaxies
1. Spiral
2. Elliptical
3. Irregular

3. Spiral Galaxies: Arms spiral outward like a pinwheel
Our galaxy, The Milky Way, is a spiral galaxy

4. Elliptical Galaxies: Look like flattened balls or a football.
Have billions of stars, but little gas and dust.
Contain the oldest stars

5. Irregular Galaxies
No definite shape
Example: Large Magellanic Cloud

6. ( Light will travel 9.5 million, million kilometers in one year!)
Scientists use LIGHT YEARS to measure distances in space. A light year is the distance light travels in one year.
Light travels at the speed of 300,000,000 meters/second.

7. Classifying Stars Stars are classified by 3 Main Characteristics:
1. Size
2. Temperature
3. Brightness

8. Hottest (20,000-50,000*C) : (10,000*C) (6,000*C) (4,000-5,000*C)
Color reveals the temperature of a star.
Hottest (20,000-50,000*C)
: (10,000*C)
(6,000*C)
(4,000-5,000*C)
(3000*C)
Blue
White
Yellow
Red-Orange
Red

9. Brightness of Stars
Apparent Magnitude: Brightness as seen from earth
Absolute Magnitude: Brightness of a star from a standard distance

10. Hertzsprung-Russell Diagram
A graph plotting brightness and temperature.
90% of stars are
Main Sequence