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NOTES: The Sun How big ? D(Jupiter) = 10 x D(Earth) D(Sun) = 10 x D(Jupiter)PowerPoint Presentation

NOTES: The Sun How big ? D(Jupiter) = 10 x D(Earth) D(Sun) = 10 x D(Jupiter)

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How big? D(Jupiter) = 10 x D(Earth)

D(Sun) = 10 x D(Jupiter)

More precisely, D(Sun) = 109 x D(Earth) . (See overlay)

Or 1.3 million Earth volumes.

How massive? M(Sun) = 330,000 M(Earth) .

How far? 1 AU = 1.5x108 km = 8.3 light mins (Pluto-5.5 lt hrs)

How bright? Power output at source = Luminosity,

L = 4 x 1026 watts. Enough power to cover surface with

100 watt tiny Christmas tree lights.

How bright at Earth? Solar Constant = 1,370 watts/m2.

Like 14 100 watt bulbs.

Content? See abundance overlay.

How big? Roughly (diameters)

D(Jupiter) = 10 x D(Earth)

D(Sun) = 10 x D(Jupiter)

More precisely,

D(Sun) = 109 x D(Earth) .

Or 1.3 million Earth volumes.

How massive? M(Sun) = 330,000 M(Earth) . Found using

Newton’s version of Kepler’s 3rd Law.

1 AU = 1.5x108 km = 8.3 light mins (Pluto-5.5 lt hrs)

About 8,000 Pluto distances to the nearest star—Alpha Centauri

How bright at Earth? Solar Constant = 1,370 watts/m2.

Like 14 100 watt bulbs. However, solar panels

are less than 50% efficient.

World’s largest solar facility—produces 150 megawatts.

How many square meters could produce this?

Three means of energy transfer:

Conduction (throughout), Convection, and Radiation.

Photosphere:

T= 5700 K

Chromosphere

T = 15,000 K

Corona

T = 2 million K

Radiation: high energy gamma rays emitted in core

are absorbed and re-emitted as multiple photons,

degrading energy. This is called the random walk.

It takes 1-10 million years for energy to reach the sun's surface.

Core: T = 15 million K

Source of Energy (Nuclear Fusion):

P-P Process: Protons must have enough energy to overcome

electric repulsion and fuse together.

This means 10 million degrees K (Kelvin = Centigrade + 273).

Dominates in stars less than 1.5 solar masses.

p + p --> D + positron + neutrino

p + D --> 3He + gamma ray

2 3He --> 4He + 2p

CNO Process: In stars above 1.5 solar masses there is recycled

carbon in the core, which works as a catalyst for fusing protons

into Helium 4. Catalyst: unchanged, but facilitates process.

Spectrum: Continuous spectrum with hundreds of dark lines.

Peak wavelength gives surface temperature

T = 5700 K of photosphere. We can see into various depths

by looking out at toward the limb, or sun's edge.

- Sunspots: Maximum every 11 years.
- Sun's magn. pole also flips every 11 years.

We know we have intensified magnetic fields in sunspots

by the amount certain spectral lines are split apart by the

Zeeman effect.

No sunspots from 1650-1715 AD--Maunder minimum.

No one knows why, or whether it will happen again.

Sunspots are associated with flares, prominences,

and coronal mass ejection.

Babcock's dynamo theory utilizes

differential rotation to explain the variations in sunspots.

It’s like a rubber band being wrapped around sun as

it rotates. If will break eventually solar minimum.

The solar wind of electrons (and a few protons)

is increased during sunspot maximum and by solar flares.

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