Chapter 29 Notes

Stars

The Sun: Solar Atmosphere

• Photoshere: visible surface, 5800 K

• Chromosphere: 30,000 K

• Corona: 1 to 2 million K, solar wind extends from the corona

Solar Interior

• Core: nuclear fusion• Radiative zone:

energy moves outward from the core

• Convective zone: currents carry energy to the surface

Solar Activity

• Sunspots—11 year cycle• Solar wind• Prominences

Solar Energy

• Nuclear fusion takes place in the core of the sun

• Hydrogen nuclei fuse together to form helium• Energy is released• E=mc2 (E = Energy, m = mass, c = speed of light)

• When hydrogen is gone, stars will form carbon, oxygen, neon, silicon, and iron—in that order

Electromagnetic Spectrum

• Dark bands in the visible spectrum are caused by different chemical elements

• 70% hydrogen 28% helium

Measuring Stars

• Parallax is used to find the distance to stars

• Constellations: Groups of stars in the same part of the sky

• Clusters: groups of stars bound together by gravity

• Binaries: two stars that orbit a common center of mass

Doppler Shift

• Movement of a star affects the frequency of the light waves

• Stars moving toward us are blueshifted, stars moving away are redshifted

Star Properties

• Magnitude– Apparent magnitude: how bright the star appears

from Earth– Absolute magnitude: how bright a star would look

if it were 10 parsecs away

• Luminosity: energy output per second • Composition of stars: ~73% hydrogen, ~25%

helium, ~2% all other elements

Temperature

• Temperature determines spectral class and color

• Blue stars are hotter, red stars are cooler

• Oh, be a fine girl, kiss me.

Spectral Types of Stars

Star Life Cycle

• Stars spend most of their “life” in the Main Sequence and so most stars are located in the Main Sequence section of the H-R diagram

• Small mass stars burn fuel slowly and have a long life span

• Large mass stars burn their fuel very quickly and are much brighter than small mass stars

Star “Life-Cycle”

• Mass determines the future of a star