ConceptChecks
ConceptCheck 16-1: The Sun emits most of its energy in the form of visible light.
ConceptCheck 16-2: At the extremely high temperatures and pressures existing in the Sun’s core, hydrogen nuclei can move fast enough to overcome the repulsive force from their positive electric charges and fuse together.
ConceptCheck 16-3: When 1 kg of hydrogen combines to form helium, the vast majority of the mass ends up in helium atoms, with only 0.7% of the original mass converted into energy.
ConceptCheck 16-4: Astronomers use the current energy output of the Sun to estimate how fast the Sun is consuming its usable fuel (hydrogen). Then, the amount of hydrogen fuel remaining in the Sun’s core indicates how much longer the Sun will shine.
ConceptCheck 16-5: Because pressure in the Sun’s core is due to the downward pushing weight of the overlying mass of material, having less mass pressing down would result in a lower pressure at the core.
ConceptCheck 16-6: The energy transport process of conduction occurs when energy moves through a relatively dense material by hot material transferring its kinetic energy to cooler material through direct contact. The Sun’s density is simply too low for conduction to be an important process in transferring energy from one part of the Sun to another part.
ConceptCheck 16-7: Only the temperature decreases with increasing distance from the Sun’s central core.
ConceptCheck 16-8: As shown in Figure 16-5, sound waves do penetrate into the Sun, which allows helioseismologists to study the solar interior.
ConceptCheck 16-9: By carefully monitoring how sound waves move through the Sun, astronomers are able to deduce the amount of helium in the Sun’s core and convective zone, and the thickness of various zones.
ConceptCheck 16-10: Kamiokande could only detect one of three possible types of neutrinos, and this was the type emitted by the Sun. However, along the way, two-thirds of these neutrinos transformed into the other types and were undetectable by Kamiokande. SNO, on the other hand, was able to detect all three types of neutrinos.
ConceptCheck 16-11: The energy transport process of convection causes warmer material to rise to the surface and cooler material to sink back into the photosphere, giving the photosphere a granulelike appearance.
ConceptCheck 16-12: Figure 16-11 is taken with an Hα filter that only allows red light to pass through and form the image. This method is used to block out the Sun’s other light that would overwhelm the camera. Since the Hα line is red (at 656.3 nm), the spicules appear red, but they emit other wavelengths as well.
ConceptCheck 16-13: The corona has an extremely low density and can only be observed when the more dominant photosphere is blocked, such as during a solar eclipse.
ConceptCheck 16-14: The solar wind must escape through the corona, and this occurs in greater abundance through holes in the corona that contain less gas.
ConceptCheck 16-15: The photosphere surrounding a sunspot has a temperature of about 5800 K, which far outshines the relatively cooler sunspot region, resulting in the sunspots appearing to be quite dark in comparison.
ConceptCheck 16-16: The length of time between large numbers of sunspots to few numbers of sunspots and back to large numbers of sunspots averages about 11 years. However, the magnetic character of sunspots flips every 11-year cycle, suggesting an overarching 22-year sunspot cycle.
ConceptCheck 16-17: According to the magnetic-dynamo model, the sunspot cycle is a result of twisting magnetic fields. In the event the Sun was turning faster, the twisting would occur more quickly and the length of the sunspot cycle would decrease.
ConceptCheck 16-18: The glowing plasma tends to follow the pathways created by the Sun’s invisible magnetic field lines, which form curved arches above the Sun’s surface.
ConceptCheck 16-19: Coronal mass ejections are many times more energetic than any other event on the Sun and, when directed at Earth, can cause severe problems with telecommunications, electrical power distribution, and radiation health hazards for astronauts working in space.
CalculationChecks
CalculationCheck 16-1: According to Einstein’s equation that E = mc2, a mass of 5 kg is equivalent to 5 kg × (3 × 108 m/s)2 = 15 × 108 joules, which is equivalent to burning about 100,000 metric tons of coal!
CalculationCheck 16-2: According to Figure 16-3, the Sun’s core temperature is about 16 million Kelvins. At a distance of 50% of the Sun’s radius, the Sun’s temperature has dropped to 4 million Kelvins, which is a drop of about 75%.