4. Constellation

A. A grouping of stars (ex. Big Dipper) - named after animals, mythological

creatures, and everyday objects.

4. Constellation - Today, there are 88.

- Some constellations you can see year-round, others only in specific seasons.

Star Cluster- A group of stars that is gravitationally bound to each other- they interact with each other.

Binary Stars- two stars that orbit around a common center of mass, and are very close to each other.

5. Stellar Distances

A. Light year - the distance light

travels in a year - (it has nothing to do with time). - It is 9,500,000,000,000 km. - Used to show distance to stars

5. Stellar Distances –

B. Parallax - the METHOD used to determine the distance to stars. - The star appears to move because Earth is moving. - Scientists can look at the angle of apparent movement to determine how far away the star is.

6. Star Color vs. Star Temperature

A. Hot Stars- stars that are 30,000 K or hotter are blue.

B. Medium Stars- stars in the middle range appear yellow.

C. Cool Stars- stars in the 4,000 K

or less range are red.

6. Star Color vs. Star Temperature

7. Hertzsprung-Russell Diagram

A. Y-axis is absolute magnitude

B. X-axis is the temperature of star

7. Hertzsprung-Russell Diagram

C. Main Sequence Stars

- Stars on a curve that runs diagonally through the graph

- 90% of all stars are main sequence.

- Hot and bright stars to cool and dim stars

7. Hertzsprung-Russell Diagram

D. White Dwarf

- Small, dim, and hot

- Few are White Dwarfs

E. Red Giants

- Large, bright and cool

- Few are Red Giants

7. Hertzsprung-Russell Diagram

F. Our sun is average in size and temperature (main sequence star)

Star Composition

Most stars are about 73% hydrogen and 25% helium!!