Science of Sunlight

Running Head : INTERNAL STRUCTURE OF THE SUN

Internal Structure of the Sun and its Discoverers

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Internal Structure of the Sun and its Discoverers

The sun is the only star in the solar system . It accounts for almost 99 .8 of the solar system 's mass . It is composed of about 74 hydrogen (which accounts 92 of its volume , 25 helium (7 of volume , and other elements . It has a surface temperature of 5780 Kelvin , giving a white color (the process called scattering makes the sun appear yellow

as viewed from the earth 's surface . It is classified as a yellow star orbiting the center of the Milky Way galaxy at an orbital speed of 217 km /s . It is estimated that it will complete its orbit in about 225-250 million years

Generally , the sun has five major parts : 1 ) the core , 2 ) the radiation zone , 3 ) the convection zone , 4 ) the photosphere , and 5 ) the atmosphere The first three are the internal structures of the sun the second external /surface structures . The energy derived from this fusion escapes to the radiation zone . It is estimated that the solar core extends from its center to about 0 .2 solar radii . It has a density of 150 , 000 kg /m3 (which is almost 150 times the density of water on earth . It has a temperature (which varied depending on the temperature gradient of sections of the core ) close to 13 , 600 , 000 K (which is considered high when compared to its surface temperature . The solar core rotates at a speed still undetermined by astronomers (although approximations were presented . Nuclear fusion happens in the solar core . Hydrogen is fused to form different isotopes of helium . Nuclear fusion though in the core occurs in a series of steps called p-p (proton-proton ) chain . In this process , hydrogen atoms combined to form a specific isotope of helium This process produces energy (which is in the form of heat . The rate though of fusion depends on density and temperature . A slight different in the rate of fusion may cause the core to release more energy and therefore expand against the weight of other solar layers . This stimulates the reduction of the fusion rate and thus returns to its normal condition (self-equilibrium . All the energy travel through successive layers of the sun (heat naturally escapes from a dense material . Some heat escapes to the solar photosphere and then to space . The second and third internal structures of the sun are the radiation and convection zones . The radiation zone ranges from 0 .2 to approximately 0 .7 solar radii . This zone has a lower temperature and density than the solar core . It does not allow nuclear fusion to occur in the early and middle stage of a star 's life cycle . Thermal radiation occurs in the radiation zone . This process allows the transfer of intense heat from the core to the outer layers of the sun . The heat generated in the core passes to the radiation zone and then to the convection zone . Since the surface density and temperature of the convection zone is insufficient to allow thermal radiation , thermal columns serve as the carrier of hot material to the photosphere . Once the material cools down , it goes back to the convection zone , and is reheated . It then shoots to the sun 's photosphere

There are four ways to measure the density , radius , and the temperature of the sun 's interior . The first is called hydrostatic equilibrium . It is the condition where outward pressure balances inward force . In the case of the sun , the determination of the approximate value of its inward force led to the determination of the outward force (they are not always equal variations occur and constants are given . The second is called thermal equilibrium . It is the state where the amount of energy generated equals the amount radiated away . In the case of the sun , the determination of the amount of energy radiated resulted in the determination of the approximate temperature gradient (and density ) of the sun 's interior . The third is opacity . It is the resistance of the solar envelope to the flow of photons . The measure of resistance is equal to the measure of density and temperature gradient of the radiation zone . The last is called energy transport . It is the process of transporting energy from the core to the photosphere . The rate of energy transport allows astronomers to determine the rate of resistance in the solar layers , and consequently to its specific temperature and density

Reference

The interior of the sun (2007 . Retrieved on October 19 , 2007 from http / http /csep10 .phys .utk .edu /astr162 /lect /sun /interior .html

Related Links

HYPERLINK "http /zebu .uoregon .edu js /ast121 /lectures /lec22 .html http /zebu .uoregon .edu js /ast121 /lectures /lec22 .html

HYPERLINK "http /ircamera .as .arizona .edu /NatSci102 /lectures /suninterior .htm http /ircamera .as .arizona .edu /NatSci102 /lectures /suninterior .htm

http /www .windows .ucar .edu /tour /link /sun /solar_interior_new .html edu h igh

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