The Sun

The Sun• Our closest star (a yellow dwarf)• Source of all energy on Earth• Located 149 million km from

Earthor 1 AU (Astronomical Units)

• Light takes a million years to get from the core to the Sun’s surface but only 8 minutes to reach us

The Sun•Rotates on its axis and orbits

the galaxy, same as us•About half way through its

10 billion year life cycle•Sun will swell into a red

giant, then cool to form a brown or black dwarf

The Sun

The Core•25% of its radius•Intense pressure causes

nuclear fusion – atoms of hydrogen fuse to form helium

•Gives off huge amounts of energy (a billion 1 Mt nuclear blasts per second)

The InteriorRadiative Zone•45% of Sun’s radius•Energy carried out by

photons (light energy)•Takes huge amount of time

to get through

The InteriorConvective Zone•30% of Sun’s radius•Waves of hot gas•Carry energy outward to

surface

The Atmosphere

• Made up of 3 parts: the photosphere, the chromosphere, and the corona

The AtmospherePhotosphere•The surface of the Sun •300 – 400 km wide•6000˚ Celsius

The AtmosphereChromosphere•Above photosphere (about

2000 km)•Convection currents cause

temp. to rise to 10000˚ Celsius

The AtmosphereCorona•Extend millions of km out in

space•Best seen during a solar

eclipse or X-ray of the Sun•About 1000000˚C – perhaps

due to Sun’s magnetism

Solar X-Ray

Photosphere

Chromosphere

Corona

Other FeaturesSunspots•Darker, cooler regions on

the surface• Intense magnetic field•Runs in an 11 year cycle

(2010 is when sunspots are at a minimum)

Other FeaturesProminences• Clouds of gas from the

chromosphere• Rise up along magnetic lines from

sunspots

Solar Flares• Violent eruptions from the Sun• Release intense radiation which

cause auroras (Northern Lights)

Life of a Star•The fate of a star depends on

its sizeDwarf Stars•Like our sun, will swell up (red

giant) then slowly burn out (white dwarf then black dwarf)

•Will take several billion years

Fate of the Sun• http://videos.howstuffworks.com/science-channel/6566-destiny-the-suns-fate-video.htm

Life of a StarHuge or Giant Stars•Will become a supergiant,

then explode into a supernova (core instantly collapses)

•Eventually ends up as a neutron star or a black hole

Neutron Star• 1.5 – 3 times

mass of Sun• Core shrinks to

diameter of 10 km, mass still double the Sun

• Huge magnetic field and rapid spin

Black Hole• > 3 times

mass of Sun• Contracts

tremendously• Gravitation

pull so strong not even light can escape!