Chapter 29

Sec 1Structure of the sunPeople believed the suns energy came from fireThey believed the sun burned some type of fuel to produce energy< 100 yrs ago, scientists discovered the source of suns energy

The Suns EnergySun is too bright to look at with naked eyeAstronomers use special filters and specialized scientific instrumentsComposition of the sunSpectrograph is used to break suns light into spectrumStudying the spectrum, scientists determine amts of elements present in the stars atmosphere

Composition of sun cont.Hydrogen- about 75%Helium about 24%Total amount of these two gases 99% of the suns massTrace amounts of other elements

Nuclear FusionThe process of combining nuclei of small atoms to form more-massive nuclei.Fusion releases huge amts of energyNuclei of H atoms primary fuel for the suns fusionH 1 p+ 1 e- Inside the sun e- are stripped from the P+ by sun intense heat

3 steps to Nuclear fusionFigure 2 page 756Step1 --- 2 H nuclei (P+) collide and fuse+ charge of one of the P+ is neutralized as that particle emits a particle called a positron This results in the P+ becoming a N0 which changes the original 2 P+ into a Proton/Neutron pairStep 2 --- another P+ combines with this proton/neutron pair which produces a nucleus of 2 P+ and 1 N0

Step 3 --- 2 nuclei make up the 2 P+ and 1 N0 collide and fuseAs this fusion happens 2 p+ are releasedThe remaining 2 P+ and 2 N0 fuse together and form a Helium (He) nucleusDuring EACH step of the reactions ENERGY is RELEASED

The Final ProductOne final product of fusion of H is always a He nucleusHe nucleus 0.7% < mass than H nuclei that combined to form it and the lost mass is converted to ENERGY during the series of fusion reactions that form He

Mass Changing Into EnergyFusion > suns energyMass lost during fusion > energy1905 Albert Einstein proposed that a small amt of matter yields a LARGE amt of energyNuclear fusion unknown at the timeNucleus of atom not yet discoveredEinsteins Theory of Relativity included E = mc2Where E is energy producedm is mass and c2 is speed of lighthttp://fuse.pha.jhu.edu/outreach/kit1/lightspeed.html

Einsteins equation helped astronomers to explain the huge quantities of energy produced by the sunSun changes 600 million tons of H into He every secondThis amt of H is small compared to the total amt of H in the sun

Copy figure 4 page 758 The Suns interiorScientists cant see directly so models are usedMotion of suns surface aids in studying its interior*The core 25% of total diameter of 1,380,000 kmTemp of core 15,000,000 0C and is ionized gasNo liquid or solid exists at this temp

*The Radiative Zone The zone surrounding the coreTemp ranges from 2,000,000 to 7,000,000 0Cenergy in this zone moves outward in the form of electromagnetic waves, or radiation*The convection Zone surrounds the radioactive zoneTemp 2,000,000 0CEnergy produced in the core moves through this zone through convection (the transfer of energy by moving matter)

Convection zone cont.Hot gases carry energy to the surfaceHot gases move outward, expand, and lose energyCooling gases denser and sink to the bottom of the conv. Zone where they are heated again by the radiative zone and rise againThus, Energy is transferred to the suns surface as gases rise and sink

The Suns Atmospherehas 3 layersThe photosphere sphere of light innermost layer made of gases that have risen form the convection zone temp 6,000 0C most energy given off here in the form of visible light layers are transparent so the visible light is seen from Earth sunspots cool areas/dark spots 3,800 0C page 759 fig 5

2. The Chromosphere color sphere thin layer of gases glows with reddish light typical of H temp range 4,00 50,000 0C gases in chromosphere move away from the photosphere3. The suns Outer Parts corona (crown) is the outermost layer huge region of gas - temp above 1,000,000 0CNot very dense magnetic field prevents most atomic parts from escaping into space e- & ions can escape produce solar winds which flows out from the sun to the rest of the solar system

Sec. 2 Solar ActivitySunspots cool dark areas of gas within the photosphere strong magnetic fields on regions of the sun lead to sunspots because CONVECTION slows and ENERGY decreasesThe sunspot cycle lasts 11 years sunspots showed astronomers that the sun rotates

Solar EjectionsEvents in which the sun emits atomic particlesInclude prominences, solar flares, coronal mass ejections

Solar activity- cycle is caused by the changing solar magnetic field

ProminencesA disturbance in the suns atmosphere caused by the magnetic fields - Great clouds of glowing gases that form huge arches that reach high above the suns surface commonly associated with the chromosphere

Solar FlaresMost violent solar disturbance a sudden eruption of electrically charged particles (e- and p+) trigger for this is unknown they release energy stored in the strong magnetic fields temp of flares reach 20,000,000 0C

Coronal Mass EjectionsSome flare particles escape into space. these particles increase the strength of solar winds some particles escape into space as CME parts of the corona thrown off the sun read more on page 763(how sun affects day to day life on Earth)

AurorasOn Earth, spectacular effect of the interaction between the solar wind and Earths magnetosphere is the bands of light called auroras-Usually seen close to the magnetic poles usually occur after solar flares occur Northern lights and Southern lights