The Properties of Our Sun

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Slide 1

THE SUN

The star we see but seldom notice

Slide 2

Goals

Summarize the overall properties of the Sun.

What are the different parts of the Sun and how do we know this?

Where does the light we see come from?

Solar activity and magnetic fields.

Slide 3

The Sun, Our Star

The Sun is an average star.

From the Sun, we base our understanding of all stars in the Universe.

Like Jovian Planets it’s a giant ball of gas.

No solid surface.

Slide 4

Vital Statistics

Radius = 100 x Earth (696,000 km)

Mass = 300,000 x Earth (1.99 x 1030 kg)

Surface temp = 5780 K

Core temp = 15,000,000 K

Luminosity = 4 x 1026 Watts

Solar “Day” =

24.9 Earth days (equator)

29.8 Earth days (poles)

Slide 5

Structure

‘Surface’

Photosphere

‘Atmosphere’

Chromosphere

Transistion zone

Corona

Solar wind

‘Interior’

Convection zone

Radiation zone

Core

Slide 6

The Solar Interior

How do we know what’s inside the Sun?

Observe the outside.

Theorize what happens on the inside.

Complex computer programs model the theory.

Model predicts what will happen on the outside.

Compare model prediction with observations of the outside.

Scientific Method!

Slide 7

Helioseismology

Continuous monitoring of Sun.

Ground based observatories

One spacecraft (SOHO)

Surface of the Sun is ‘ringing’

Sound waves cross the the solar interior and reflect off of the surface (photosphere).

Slide 8

Interior Properties

Core = 20 x density of iron

Surface = 10,000 x less dense than air

Average density = Jupiter

Core = 15,000,000 K

Surface = 5780 K

Slide 9

Do you see the light?

Everything in the solar system reflects light.

Everything also absorbs light and heats up producing blackbody radiation.

Q: Where does this light come from?

A: The Sun.

But where does the Sun’s light come from?

Slide 10

Our Journey through the Sun