Chapter 14- Sun

Question 1

Energy

Answer 1

Generated in the core of the sun by the nuclear fusion of hydrogen into helium. Released mostly into gamma rays- high energy photons.

Energy moves very slowly, takes hundreds of thousands of years for the energy to move from the core to the point where density is low enough that convection is better than radiation.

Whereas air heated by Earth’s surface expands and becomes less dense, hot, dense plasma from the Sun moves outward and away from the convection zone.

Convection- materials carry energy with them as they move place to place

Question 2

Photosphere

Answer 2

Visible layer of the sun, about 500 km thick.

Below this layer the Sun is too dense to allow a photon emitted there to escape. This layer is not seen.

Above this layer it is too thin to emit radiation.

Question 3

Granulation

Answer 3

Convection cells bursting out on the surface. How energy reaches the photosphere.

Question 4

Spectrum of photosphere

Answer 4

Dominated by dark absorption lines. Cool outer layers of the photosphere contain atoms which absorb specific wavelengths of the continuous spectrum emitted from the hotter layers below

Question 5

Limb darkening

Answer 5

Edge of the sun looks darker than the center. Caused by a steady drop in temperature from the core of the Sun to the base of the photosphere to the top of the photosphere.

Question 6

Chromosphere

Answer 6

Layer above the photosphere where the temperature begins to rise again about 10,000 K in about 1600 Km. Characterized by emission lines.

Covered by spicules (“spikes”) which develop above sunspot groups on the photosphere because the magnetic fields there exert pressure on the atmosphere above.

Also shows filaments- long dark streaks from which prominences erupt.

Question 7

Corona

Answer 7

Characterized by highly ionized atoms, like Fe XIV (iron with thirteen electrons removed).

It takes violent collisions to produce such ions, and this indicates temperatures around 2 million K. However, the corona is so rarefied that there is little energy associated with these high temperatures.

These temperatures cause the corona to stream away from the sun in the form of solar wind.

Shape is rather irregular. There are coronal holes from which huge coronal mass ejections occur sending additional streams of charged particles outward through the solar system.

Question 8

Solar Activity Cycle

Answer 8

Sun has a magnetic field like Earth. Sun experiences differential rotation; equatorial regions rotate faster than the polar regions.

Question 9

Sunspots

Answer 9

Magnetic field of the Sun originates in the convection zone rather than the core. As the Sun rotates, this becomes twisted and can break through the photospheric surface. This causes sunspot groups to form.

Twisted tube of field lines leading to a sunspot inhibits the flow of plasma in the convection current. The sunspot is cooler and darker than the surrounding photosphere.

At the beginning of sunspot cycle,a few form around 30 degrees N and S latitude. At the solar maximum, many spots form around 15 degrees. Then they become less numerous. Takes about 11 years to complete.

Sunspots do affect earth. 1645-1715, Maunder Minimum. Period of little sunspots that correllates with Little Ice Age in Europe, huge drought in NA

1859 Solar Flare- knocked out telegraph system.