Chapter 28 The Chapter 28 The SunSunCh. 28.1 Structure of the SunCh. 28.1 Structure of the Sun

The CoreThe Core

10% of sun’s total diameter of 1,300,000 10% of sun’s total diameter of 1,300,000 km.km.

Core temp. is about 15,000,000 C.Core temp. is about 15,000,000 C. Dense gas, with very strong gravity Dense gas, with very strong gravity

making the core 10 times denser than making the core 10 times denser than iron.iron.

Heat causes electrons to be stripped Heat causes electrons to be stripped from core’s atoms…the exposed nuclei from core’s atoms…the exposed nuclei can be changed by nuclear fusion. can be changed by nuclear fusion.

Hydrogen FusionHydrogen Fusion

Hydrogen protons undergo fusion in a Hydrogen protons undergo fusion in a five-step process.five-step process.

Energy is released during each step in Energy is released during each step in the process.the process.

End result is a helium nucleus.End result is a helium nucleus. Mass of helium has about 0.7% less Mass of helium has about 0.7% less

mass than the hydrogen that formed it.mass than the hydrogen that formed it. Lost mass was converted to energy.Lost mass was converted to energy.

Mass into EnergyMass into Energy

Einstein’s theory of relativity proposed Einstein’s theory of relativity proposed that mass and energy were that mass and energy were interchangeable according to the formula interchangeable according to the formula E=mcE=mc22..

E is energy produced.E is energy produced. m is mass.m is mass. c is the speed of light, 300,000 km/s. c is the speed of light, 300,000 km/s.

Small amount of matter produces a very Small amount of matter produces a very large amount of energy.large amount of energy.

The sun converts 600 million tons of The sun converts 600 million tons of hydrogen into helium each second.hydrogen into helium each second.

Other complex fusion reactions occur Other complex fusion reactions occur with nuclei of carbon, nitrogen, and with nuclei of carbon, nitrogen, and oxygen, producing energy.oxygen, producing energy.

The Inner ZonesThe Inner Zones

Two zones to pass through before Two zones to pass through before energy produced in the core reaches the energy produced in the core reaches the sun’s atmosphere.sun’s atmosphere.

Radiative ZoneRadiative Zone—surrounds the core. —surrounds the core. Energy moves from atom to atom.Energy moves from atom to atom.

Temp. is about 2,500,000 C.Temp. is about 2,500,000 C. Energy in the form of electromagnetic Energy in the form of electromagnetic

radiation.radiation.

Convective ZoneConvective Zone—surrounds the —surrounds the radiative zone. Temp. about 1,000,000 Cradiative zone. Temp. about 1,000,000 C

Energy moves through by convection Energy moves through by convection (heat transfer by moving gases or (heat transfer by moving gases or liquids).liquids).

Rising gases transfer heat to the surface.Rising gases transfer heat to the surface. Gases continuously rise and sink.Gases continuously rise and sink.

The Sun’s AtmosphereThe Sun’s Atmosphere

The three uppermost regions of solar The three uppermost regions of solar gases.gases.

PhotospherePhotosphere—innermost layer. The —innermost layer. The layer we see. Temp. about 6000 C. layer we see. Temp. about 6000 C. Grainy appearance called Grainy appearance called granulationgranulation due to convecting gases.due to convecting gases.

Considered the surface of the sun.Considered the surface of the sun.

ChromosphereChromosphere—layer above the —layer above the photosphere. Thin layer that glows with photosphere. Thin layer that glows with reddish light. Temp. from 4000 to 50,000 reddish light. Temp. from 4000 to 50,000 C.C.

CoronaCorona—outermost layer. Gases blend —outermost layer. Gases blend into space. Heated to about 2,000,000 C into space. Heated to about 2,000,000 C by sun’s magnetic field. Prevents most by sun’s magnetic field. Prevents most atomic particles from escaping into atomic particles from escaping into space. Some do escape through holes, space. Some do escape through holes, and form the and form the solar windsolar wind..

Corona normally not seen, but becomes Corona normally not seen, but becomes visible during a solar eclipse.visible during a solar eclipse.