1. Characteristics of Stars
Constellations – imaginary patterns of stars
Circumpolar – five constellations in the Northern Hemisphere that circle the pole star (Polaris)
Classification of Stars
Stars are classified by their color, temperature, size, brightness, and composition

2. Brightness depends on size and temperature and there are two types
Composition is determined by a spectrograph – a device that breaks light into colors and produces an image of the resulting spectrum
Brightness depends on size and temperature and there are two types
Apparent – brightness as seen from Earth
Absolute – brightness the star would have if it were at a standard distance from Earth
Measuring Distance
Astronomers use light years – the distance that light travels in one year, about 9.5 million million kilometers
Astronomers use parallax – the apparent change in position of an object when you look at it from different places

3. Hertzsprung-Russell (HR) Diagram
graph used to determine a stars classification
it helps identify stars by color, size, temperature and brightness.
about 90% of stars fall on the main sequence.
the other 10% of stars were once main sequence stars.
can help determine where a star is in its lifecycle