OUR SUNOUR SUNTHE CLOSEST STARTHE CLOSEST STAR

Composition of the SunComposition of the SunThe Sun is composed of at least 80 of the The Sun is composed of at least 80 of the elements found on Earth.elements found on Earth.Sun is mostly composed of 91.2% Hydrogen, Sun is mostly composed of 91.2% Hydrogen, 8.7% Helium.8.7% Helium.The other elements make up just 0.1%. The other elements make up just 0.1%. These elements include O, C, and N, and These elements include O, C, and N, and other gases present in trace amounts.other gases present in trace amounts.All of these elements exist in the fourth form All of these elements exist in the fourth form of matter called of matter called plasmaplasma – matter in which – matter in which atoms have lost their electrons due to very atoms have lost their electrons due to very high temperatures, basically an ionized gas.high temperatures, basically an ionized gas.

How does the Sun How does the Sun produce Energy?produce Energy?

Thermonuclear reactions occur in the Thermonuclear reactions occur in the core of the Sun to produce its energy.core of the Sun to produce its energy.Hydrogen fuses to helium Hydrogen fuses to helium → nuclear fusion → nuclear fusion

E = mcE = mc2 2 Einstein’s mass-energy Einstein’s mass-energy equivalence formula: Four H nuclei combine equivalence formula: Four H nuclei combine in a series of steps to form He. He has in a series of steps to form He. He has slightly less mass than the H from which it slightly less mass than the H from which it derived. The “missing mass” is converted derived. The “missing mass” is converted into energy in the form of heat. into energy in the form of heat.

The Structure of the SunThe Structure of the Sun

The Inner ZonesThe Inner Zones

The CoreThe CoreCenter of the SunCenter of the Sun

10% of Sun’s diameter10% of Sun’s diameter

15,000,00015,000,000 C CSun’s gravity is so strong that the core is Sun’s gravity is so strong that the core is 10X denser than Fe.10X denser than Fe.

Nuclear fusion occurs here. H fuses to He Nuclear fusion occurs here. H fuses to He resulting in energy in the form of heat.resulting in energy in the form of heat.

Radiation ZoneRadiation ZoneZone surrounding the coreZone surrounding the core

7,000,0007,000,000 C to 2,000,000 C to 2,000,000 C C

PhotonsPhotons move from atom to atom in form move from atom to atom in form of waves. Their path is so slow it may of waves. Their path is so slow it may take a million years for a photon to reach take a million years for a photon to reach the surface.the surface.

Radiation is the transfer of energy (heat, Radiation is the transfer of energy (heat, light, etc.) through a wave motion.light, etc.) through a wave motion.

Convection ZoneConvection ZoneEnergy is carried from the radiative zone Energy is carried from the radiative zone to the convective zone – hot gases boil up to the convective zone – hot gases boil up in giant convective cells.in giant convective cells.

Hot gases move the energy to the surface Hot gases move the energy to the surface of the sun, then cool and sink again, ready of the sun, then cool and sink again, ready to pick up more energy.to pick up more energy.

2,000,0002,000,000 C to 5700C to 5700 C.C.

The Sun’s AtmosphereThe Sun’s Atmosphere

The PhotosphereThe PhotosphereInnermost layer of the Innermost layer of the Sun’s atmosphere.Sun’s atmosphere.Only part of the Sun we Only part of the Sun we can see directly.can see directly.58005800 – 6000 – 6000 C. C.GranulationGranulation – convection – convection cells bubble to surface cells bubble to surface and give surface a grainy and give surface a grainy appearance.appearance.

The ChromosphereThe Chromosphere

Above photosphere.Above photosphere.

Called “color sphere” because of its Called “color sphere” because of its faint reddish color.faint reddish color.

Can only be seen during total eclipse.Can only be seen during total eclipse.

57005700 – 100,000 – 100,000 CC

The CoronaThe CoronaOutermost layer of the Sun’s atmosphere.Outermost layer of the Sun’s atmosphere.

Only visible as a halo around the Sun Only visible as a halo around the Sun during a total eclipse.during a total eclipse.

Temperatures up to 3,000,000Temperatures up to 3,000,000 C. C.

Solar wind blows outward into space from Solar wind blows outward into space from this layer.this layer.

Activity of the SunActivity of the Sun

ProminencesProminences

Strong storms on the Sun that appear in Strong storms on the Sun that appear in the form of arching loops of hot gas from the form of arching loops of hot gas from the Sun’s surface.the Sun’s surface.

Occur near sunspots.Occur near sunspots.

Seem to be controlled by and travel along Seem to be controlled by and travel along the Sun’s magnetic field. the Sun’s magnetic field.

Solar FlaresSolar FlaresMore violent than More violent than prominencesprominencesClearly linked to the magnetic Clearly linked to the magnetic fieldfieldCan interfere with our radio Can interfere with our radio communications & cause communications & cause power blackoutspower blackoutsAlmost always near sunspot Almost always near sunspot groupsgroupsParticles ejected by flares Particles ejected by flares and carried by solar wind can and carried by solar wind can enter our atmosphere at the enter our atmosphere at the magnetic poles and cause magnetic poles and cause aurorasauroras

SunspotsSunspotsCool, dark area on the surface of the Sun.Cool, dark area on the surface of the Sun.Form in groups and may last 2 weeks to a month.Form in groups and may last 2 weeks to a month.Average spot twice the size of the Earth.Average spot twice the size of the Earth.Powerful magnetic field causes a sunspot by Powerful magnetic field causes a sunspot by inhibiting circulation of gases.inhibiting circulation of gases.11 year cycles – on average from minimum to 11 year cycles – on average from minimum to minimum.minimum.Appear 40Appear 40 to 8 to 8 above or below the Sun’s equator, above or below the Sun’s equator, but never on the equator.but never on the equator.Sunspots move across the surface as the Sun Sunspots move across the surface as the Sun rotates.rotates.Related to climatic problems.Related to climatic problems.

The Solar WindThe Solar Wind

Hot gases of the corona blown away from Hot gases of the corona blown away from the Sun.the Sun.

Contains mostly ionized H.Contains mostly ionized H.

Blows past the Earth at about 400 km/sec Blows past the Earth at about 400 km/sec and interacts with the Earth’s magnetic and interacts with the Earth’s magnetic field.field.