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Classroom Presentation about the Sun
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Slide 1

The Sun

The Sun

Our sole source of light and heat in the solar system

A very common star: a glowing ball of gas held together by its own gravity and powered by nuclear fusion at its center.

Visible Image of the Sun

Slide 2

Pressure (from heat caused by nuclear reactions) balances the gravitational pull toward the Suns center. Called Hydrostatic Equilibrium.

Pressure (from heat caused by nuclear reactions) balances the gravitational pull toward the Suns center. Called Hydrostatic Equilibrium.

This balance leads to a spherical ball of gas, called the Sun.

What would happen if the nuclear reactions (burning) stopped?

Slide 3

Main Regions of the Sun

Main Regions of the Sun

Slide 4

Solar Properties

Solar Properties

Radius = 696,000 km

(100 times Earth)

Mass = 2 x 1030 kg

(300,000 times Earth)

Av. Density = 1410 kg/m3

Rotation Period =

24.9 days (equator)

29.8 days (poles)

Surface temp = 5780 K

Slide 5

Solar Properties

Slide 6

The Solar Interior Helioseismology

The Solar Interior Helioseismology

In the 1960s, it was discovered that the surface of the Sun vibrates like a bell

Internal pressure waves reflect off the photosphere

Analysis of the surface patterns of these waves tell us about the inside of the Sun

How do we know the interior structure of the Sun?

Slide 7

How do we know the interior structure of the Sun?

Slide 8

Energy Transport within the Sun

Energy Transport within the Sun

Extremely hot core - ionized gas

No electrons left on atoms to capture photons - core/interior is transparent to light (radiation zone)

Temperature falls further from core - more and more non-ionized atoms capture the photons - gas becomes opaque to light in the convection zone

The low density in the photosphere makes it transparent to light - radiation takes over again

Slide 9

Convection

Convection

v Convection takes over when the gas is too opaque for radiative energy transport.

v Hot gas is less dense and rises (or floats, like a hot air balloon or a beach ball in a pool).

v Cool gas is more dense and sinks

Slide 10

Solar Granulation Evidence for Convection

Solar Granulation Evidence for Convection

Solar Granules are the tops of convection cells.

Bright regions are where hot material is upwelling (1000 km across).

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