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This Lecture Brought to You in Comic Sans MS

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?

Stars convert energy into matter.

E=mc^2

600 million tons of H -> 598 million tons of He

IN ONE SECOND

Proton-Proton Chain

Basic Solar Structure

The force of gravity inward and the radiation pressure outward balance each other out.

Gravitational Equilibrium

Radiation Pressure

91.2% Hydrogen – 8.7% Helium

0.1% Heavier Elements

SpectroscopyVisible Spectrum

Spectroscopy

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.

Granularity

Granularity of the Solar Surface

Convection

A Solar Prominence

Prominence

Solar Flare

Flare

Understanding the sun:

simulations

EndNEXT TIME:NEXT TIME:

Measuring the Stars