# The Lifecycle of Stars and the SunPage 1

Slide 1

The Sun

Slide 2

## Take-Away Points

The Sun is an ordinary middle-sized star

The sun creates energy by nuclear fusion in its core

The visible surface of the Sun is called the photosphere

A thin cool layer, the chromosphere, allows us to determine what the sun is made of

A very thin but very hot outer layer is called the corona

Convection in the sun is revealed by granulation

Features on the sun include sunspots, prominences, spicules and faculae

Disturbances on the sun affect electrical and electronic equipment on Earth

Slide 3

## The Sun

Distance: 150 million km (93 million miles) = 8.3 light minutes

Diameter: 1.4 million km (870,000 miles) = 109 x Earth

Mass = 330,000 x Earth

Bulk density = 1.4 gm/cc

Surface temperature = 5800 K

Rotation: 25 days at equator, 34 at poles

1. The Sun is an ordinary middle-sized star

Slide 4

## The Solar Interior

Ideal Gas Law:

Pressure x Volume is proportional to Temperature

Pressure = weight of overlying material

2. The sun creates energy by nuclear fusion in its core

Slide 5

Interior of the Sun

Slide 6

## Structure of the Sun

Core: 0-20% of radius. Energy produced by nuclear fusion

Tachocline: Boundary of Radiative Zone: Exterior slips over interior

Convective Zone: Outer 30% of Sun: Energy moves by convection

2. The sun creates energy by nuclear fusion in its core

Slide 7

## Core of the Sun

Energy output: 90 billion megatons/second

Energy output = 6 microwatts/kg – less than a candle

Human body outputs 1.2 W/kg – 200,000 times greater

By volume: Core of Sun = 0.9 W/m3; Human body = 1200 W/m3.

Trying to duplicate sun’s energy output not practical on Earth; We try to use other fusion processes

Energy takes 10,000 – 100,000 years to reach surface

2. The sun creates energy by nuclear fusion in its core

Slide 8

## Solar Energy

4 H  He

4H = 4 x 1.00794 = 4.03176

He = 4.002602

Difference = 0.029158 = 0.7% = 1/140

Converted to energy via E=mc2

Once you get over being freaked out by Einstein, this is middle school math

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