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The Sun

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The Sun

Is by far the closest star to the

Earth

Stars are luminous bodies

that create their own energythrough Nuclear Fusion

The Sun is an average star

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Nuclear Fusion

Gravity causes clouds of dust and gases

in space to contract and heat until fusion

begins

We use fission on earth (uranium and

plutonium) which does not produce asmuch energy as fusion

We only can use fusion for H-bombs

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Sunspots The sun contains

sunspots which aretemporary storms onthe suns surface.

They provideevidence that the sun

rotates once every 27days.

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Before the invention of thetelescope, the Sun was thought tobe a perfect disk. However assoon as telescopes becameavailable, astronomers turnedthem to the Sun. Theydiscovered two things. Sunspotsand blindness. Not the greatscientist Galileo though, he wasfar too clever and sensible. He

observed only at sunset andsunrise and by projecting thelight onto a screen rather thantrying to look through thetelescope itself. He drew hisresults very carefully. (1612)

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Telescope Image of Sunspots taken fromSwedish Institute of Solar Sciences

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Evolution of a Star

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Life of a Star Stars like the sun spend most of their life on

the Main Sequence. When the Suns core is all fused to He, the sun

will expand and become a Red Giant.

When the fuel is used up it will collapse into aWhite Dwarfand then a Black Dwarf

Stars more massive than the Sun will gosupernova.

Life Cycle of Stars

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Stellar Evolution

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Cassiopea A

A supernova is the final explosionof a massive star, of more thaneight solar masses. It causes abrief burst of radiation that mayoutshine the entire galaxy, before

fading from view over several

weeks or months. During thisshort interval, a supernova canradiate as much energy as theSun would emit over 10 billion

years. The explosion expels much

or all of a star's material at highvelocity, driving a shock waveinto the surrounding interstellarmedium, where it sweeps up anexpanding shell of gas and dustcalled a supernova remnant.

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Tracking a Stellar Mass

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H-R Diagram

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Luminosity and Temperature ofStars (ESRT)

Interactive HR

Diagram

Quesitons

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Questions1. In which group are the stars most

varied in both size and luminosity?

Main Sequence

2. The sun is more luminous than any starsin which group?

Dwarf

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3. State one way in which the Sun andPolaris are similar and one way in which

they are different.Similar in temp. Different in luminosity

4. Why is Betelgeuse more luminous than

St. Barnards star?It is much larger/more massive