Sunspots appear dark because they are   A) hotter than the rest of the Sun's surface. B) more magnetic than the rest of the Sun's surface.  C) cooler than the rest of the Sun's surface. D) None of the above

62. Pressure of the Photosphere. The gas pressure of the photosphere changes substantially from its upper levels to its lower levels. Near the top of the photosphere, the temperature is about 4500 K and there are about 1.6 x 1016 gas particles per cubic centimeter. In the middle, the temperature is about 5800 K and there are about 1.0 x 10" gas particles per cubic centimeter. At the bottom of the photosphere, the temperature is about 7000 K and there are about 1.5 × 10" gas particles per cubic centimeter. Use the ideal gas law (Mathematical Insight 14.2) to compare the pressures of each of these layers; explain the reason for the trend that you find. How do these gas pressures compare with Earth's atmospheric pressure at sea level?

1) What is thermal equilibrium? Is the Sun in thermal equilibrium? How do we know this? 2) In order to maintain thermal equilibrium, how much energy must the Sun generate every second?

What is the ultraviolet catastrophe?

What percentage of the energy we use comes from the sun?   25%   50%      More than 90%     Less than 10%

Why does nuclear fusion only take place in the Sun’s core?

Explain why the presence of spectral lines of a given element in the solar spectrum tells you that element is present in the sun, but the absence of the lines would not necessarily mean the element is absent from the sun.