Unit 8 Chapter 29 The Sun

We used to think that our sun was a ball of fire in the sky. Looking at our sun unaided will cause blindness. The Sun’s Energy Because the sun is so brilliant, scientists need special instruments and filters to view the sun and it’s properties. Composition of the Sun Scientists can use a spectrograph to look at the wavelengths that are emitted by the sun. They have discovered that about 75% of the sun’s mass is hydrogen and a combination of hydrogen and helium make up about 99% of the mass. Solar telescopes-allow scientists to look at the sun safely (Helios is a satellite orbiting and observing the sun). Nuclear Fusion Fusion is the combining of the nuclei of lighter elements to form heavier ones. It is the source of all stars light energy. The Final Product The energy released during the three steps of nuclear fusion causes the sun to shine and gives the sun its high temperature.

Mass Changing into Energy E=mc2 Energy = mass x the speed of light squared Because the star is a place of intense heat and pressure, the atoms are torn apart into their component nuclei and electrons. By using Einstein's equation, astronomers were able to explain the huge quantities of energy produced by the sun. The sun changes about 4 million tons of mass into energy every second. Yet this amount of mass is small compared with the total mass of the sun. Some Scientists feel that plasma is created here. Plasma is the state that helium and hydrogen exist inside a star. It is the fourth state of matter consisting of charged particles. Because of the speed that they move, they hit each other and fuse together.

The Sun’s Interior

The Core The Temperature is about 15,600,000oC It makes up about 25% of the diameter The Radiative Zone The temperatures from about 2,000,000oC to 7,000,000oC The Convective Zone The temperature is about 200,000oC In this layer, the cooler gases sink and the warmer ones rise

The Sun’s Atmosphere Surrounding the convective zone is the sun's atmosphere. Although the sun is made of gases, the term atmosphere refers to the uppermost region of solar gases. This region has three layers—the photosphere, the chromosphere, and the corona. The Photosphere This is the visible layer of the sun because most energy given off is in the form of visible light. The temperature is about 6000oC It contains dark spots that are areas with a cooler temp. 3800oC The Chromosphere Temperatures range from 6,000oC to 50,000oC It has plumes that jet out about 16,000 km from the surface It causes hydrogen to emit reddish light The Sun’s Outer Parts It is the outer atmosphere. It is very hot, about 1,000,000oC to 3,000,000oC.

Section 2 Solar Activity Sun Facts: The sun’s diameter is approximately 1,380,000km (~100 earth’s). It is 94,000,000 miles from the earth. It takes 8 minutes 20 seconds for sunlight to reach the earth. It would take 195 years at 55 mph to drive to the sun. The sun’s rotation period at the equator is approximately 25.3 earth days and 33 earth days at poles. This gives it an average rotation period of 27 earth days.

Sun Spots The Chinese were the first to discover sun spots. Galileo discovered that the spots move in a regular pattern (he went blind looking at the sun) Sun Spots are dark spots on the sun (slightly cooler than photosphere). They occur in pairs, one in north, one in south and can last for a short time like hours, days or a longer time like weeks and months. They have magnetic properties Sun Spot Cycle The cyclic period is approximately 11 years. The period starts when the spots are at peak they have about 100 and continue until they are at a low.

Solar Eruptions They are bursts of energy that leave the sun. They can be caused by solar flares (a flame leaving the sun. They can disrupt electric signals and radio transmissions due to magnetic storms they can produce.

Prominences They are great clouds of glowing gases. Some may last several weeks, some only for a few hours. Solar Flares They are the most violent disturbances. They are sudden outward eruptions of electrically charged particles that can disrupt electrical signals. Coronal Mass Ejection They are gases thrown into space.

Auroras Auroras are usually seen close to Earth's magnetic poles because electrically charged particles are guided toward Earth's magnetic poles by Earth's magnetosphere. The electrically charged particles strike the atoms and gas molecules in the upper atmosphere and produce colorful sheets of light. Depending on which pole they are near, auroras are called northern lights—or aurora borealis or southern lights—or aurora australis. It has been seen as far south as 35 degrees North