TheSun

Chapter 28

Basic Properties

• Composition of sun

HHeOCFe

0.8%

70%

28%

0.3%

0.2%

Basic Properties

• 332,000x mass then earth

• 695,000 km at equator

• 6,000°C average temp.

• Rotates 1 about every 30 days

• Age= ~5.0 billion years old

Structure of the Sun

• 3 Regions– Core– Inner Zone– Atmosphere

The Core

• ~10% of the sun• 15,000,000° C• Made up of gas• Because of gravity

the core is 10x denser than iron

The Core• Heat in the core causes electrons of the atoms

to roam free• Exposed nuclei is then changed by nuclear

reactions• Give a hydrogen fusion reaction

Hydrogen Fusion

• Step 1– 2 hydrogen nuclei collide and fuse

• Step 2– One of these protons changes into a neutron

• Step 3– Another proton combines with the proton-neutron pair, producing

a nucleus of 2 protons and 1 neutron

• Step 4– 2 of these nuclei collide and fuse

• Step 5 – Resulting cluster throws off 2 protons, leaving behind a nuclei of

2 protons and 2 neutrons

Hydrogen Fusion• Energy is given off in every step• Changes more then 600,000,000 of H into He

every sec.

Mass into Energy• 1905-Albert Einstein

proposes the Theory of Relativity

• Proposed this before nuclear physics

• E=mc²• E represents energy

produced, m represents mass, and c represents the speed of light

The Inner Zones• 2 regions within this zone

– Radiative Zone– Convective Zone

Radiative Zone

• Zone that surrounds core

• 2,500,000°C• Energy moves from

atom to atom in the form of electromagnetic waves, or radiation

Convective Zone• Zone around radiative

zone• About 1,000,000°C• Energy moves by

convection• Hot gases rise, and

cool gases sink

Sun’s Atmosphere

• Uppermost region of solar gases• Photosphere• Chromosphere• Corona

Photosphere

• Innermost layer of atmosphere• Surface of the sun-what we see ~6,000°C• Grainy appearance-Granulation

– Caused by the rising and sinking of gases from the Convective zone

Chromosphere• Chromosphere =

Color sphere• Thin layer of

gases that glows reddish light

• Temp. ranges from 4,000-50,000°C

• Gases move away and towards the photosphere

• May form narrow jets of gas that shoot outward

Corona

• Crown of the sun-Outermost layer• Huge cloud of gas heated by sun’s magnetic field ~2,000,000°C• Prevents most of the atomic particles from sun escaping into

space• Atomic particles that escape cause solar wind

Solar Activity

• Parts of the sun rotate at different speeds• Equator rotates faster than the poles

– Equator ~25 days– Poles ~33 days

• Average rotation is 27 days

• Gases in sun are in constant motion

• Energy and gravity are main reason

• Sun also rotates on its axis

Sunspots• Magnetic fields slow

down activity in convective zone

• Slower convection means less gas transfers heat

• This causes cooler areas on the surface called sunspots

• Sunspots run in a 11 year cycle

Prominences

• As a result of sunspots, prominences may form• Huge arches that reach above the surface• Each one follows a magnetic field path

Solar Flares

• One of the most violent solar disturbances• Sudden outward eruption of electrically charged atomic

particles• Cause magnetic storms on earth• Solar Flare Movie

Auroras• As a result of these

magnetic storms, the Aurora Borealis occurs

• Solar particles are attracted to the poles by the magnetosphere

• These particles come in contact with gas molecules in the upper atmosphere and produce the northern lights

Formation of the Solar System

• Each solar system that forms has four basic properties – Patterns of motion among large bodies– Two major types of planets– Asteroids and Comets– Exceptions to the Rules

Formation of theSolar System

• Solar Nebular Theory– Theory that describes

the formation of the solar system

– Accretion of particles began ≈5 bya

Formation of the Planets• As the sun was

spinning, small bodies of matter called planetismals began clumping together

• Planetsimals smash together and form protoplanets

Formation of the Planets

• These protoplanets gain mass through accretion

• Different materials in the gas cloud will condense at different temperatures

• Rock planets versus gas planets

Formation of the Planets• Frost Line

– Determines what type of planets will form– Planets beyond frost line will be gas planets– Inside of frost

line will be rockplanets

Formation of the Earth• 3 sources of heat

– Collision of planetismals– Increasing weight of the outer layers– Radioactive materials within the earth

The Solid Earth• Density Stratification

– The young earth was a giant ball of molten lava

– Heavier elements sink to the middle of planet

• Caused the earth to separate into about 3 layers– Core– Mantle– Crust

The Atmosphere• Earth managed to

capture some H and He that was in the solar nebula

• This first atmosphere was lost to space as a result of some cosmic force

Formation of the Atmosphere• Our present day atmosphere came mostly from

outgassing of materials• Outgassing is when gas escapes to the surface

from inside– Volcanoes

Formation of the OceansEventually, enough gases escaped and started tocondenseSome paleoclimatologists have speculated that theearth rained for ≈25 my

Water would evaporate instantly back into the atmosphereEventually the earth cooled and oceans began to form