Prior Knowledge Questions (Do these BEFORE using the Gizmo.) How do the appearances of stars A, B, and C in the photo at left compare? What are some ways.

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

•How do the appearances of stars A, B, and C in the photo at left compare?

•What are some ways the stars in the photo could be grouped or classified?

Chapter 29

“ Characteristics of Stars”

• Objectives:Objectives:• Describe how astronomers determine the

composition & surface temperature of a star.• Explain why stars appear to move to an

observer on the earth.• Name & describe the way astronomers measure

the distance from the earth to the stars.• Explain the difference between absolute

magnitude & apparent magnitude.

Star Composition

• All stars create light from Nuclear Fusion– Hydrogen + Hydrogen = Helium

• Also may contain: – Carbon– Oxygen– Nitrogen– Calcium

How do we know what’s in a star?

1 because of gravity

2 10,000,000 C

3 red supergiant

4 black holes

5 neutron star

6 red giant

7 planetary nebula

8 brown dwarf/black dwarf

Motion of Stars

1- Apparent Motion– circumpolar

2- Actual Motion

– Rotate on their axis– Revolve around another star– Move toward or away from the earth

Omega Centauri

PARALLAX

Huge distances in space

• Measured in parsecs (pc)

• Parsec= 3.26 light years= 3.086 x 1013 km

Stellar Magnitudes Depends on the stars brightness & its distance from space

2 scales can be used2 scales can be used

Apparent Magnitude: How it looks from EarthSun Moon Venus Jupiter Saturn Sirius

Absolute Magnitude: Also called luminosity

How it would look if we were 10 parsecs away.

“BeetleJuice” Rigel Spica Sirius

Apparent Magnitude

Absolute Magnitude