Upload
marion-nash
View
258
Download
2
Tags:
Embed Size (px)
Citation preview
Quotes“With equal passion I have sought knowledge. I
have wished to understand the hearts of [people]. I have wished to know why the stars shine.” -Bertrand
Russell
"One of the most impressive discoveries was the origin of the energy of the stars. One of the men
who discovered this was out with his girl friend the night after he realized that nuclear reactions must
be going on in the stars in order to make them shine.
She said "Look at how pretty the stars shine!" He said, "Yes, and right now I am the only man in
the world who knows why they shine." She merely laughed at him. Well, it is sad to be
alone, but that is the way it is in this world.“ - Richard Feynman, "The Feynman Lectures“
“A star shines on the hour of our meeting.” - Elvish greeting, "The Lord of the Rings“
“I wonder why. I wonder why. I wonder why I wonder. I wonder why I wonder why I wonder.” -
Richard Feynman
Readings: ASTRONOMY TODAY
Chapter 16 (excepting section 16.6)
Chapter 17 (without exception)
Readings
General Solar Properties
Percentage of Solar System Mass 99.80
Maximum Earth Distance (Km) 152,100,000
Minimum Earth Distance (Km) 147,100,000
Mean Distance from Earth (Km) 149,597,892
Earth Masses 333,400
Mass x10(30) (Kg) 1.99
Diameter of Photosphere (Earth = 1) 109.3
Diameter of Photosphere (Km) 1,390,000
Mean Density (g/cm(3)) 1.41
Solar Constant (W/m(2)) 1370
Luminosity x10(26) Watts 3.8
Spectral Class G2 V
Effective Temperature (Kelvin) 5800
Apparent Magnitude -26.7
Absolute Magnitude 4.8
Rotational Period at Equator 24d16h
Rotational Period at 40° 28d
Rotational Period at 80° 36d
Inclination to Equator to Elliptic 7°10'.5
Surface Gravity (Earth=1) 27.9
Surface Gravity m/s(2) 273
Average Sunspot Maxima (Yr.) 11.1
Average Magnetic Cycle (Yr.) 22.2
Average Escape Time for Photons Orgininating in the Core (Yr.) 10,000
Solar
Properties
Solar Properties
Why does the sun shine?
•Chemical Burning – insufficient radiation
•Radiative Cooling – only thousands of years
•Gravitational Contraction – only 25 million years
Why does the sun shine?
The force of gravity inward and the radiation pressure outward balance each other out.
Gravitational Equilibrium
Radiation Pressure
Luminosity
Luminosity
The total power output of the sun: 3.8x1024 watts!!!
Think of your 60 watt light bulb.
1 second of the earth luminosity contains enough energy tomeet our needs for roughly 500,000 years!
Only about one two-billionth of that reaches Earth.
Sun Spots
Sun Spots
Not at all dark
Roughly the size of the earth
Show the differences in rotation: 27 days equator – 31 days poles
Only about one two-billionth of that reaches Earth.