Post on 31-Dec-2015
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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