THE SUN -------- Compared to the Sun, most other stars in the Milky Way Galaxy are a) as much smaller as they look $b) smaller c) about the same size d) much larger The Sun's luminosity comes primarily from a) chemical burning. b) the mechanical energy of turbulence. $c) nuclear fusion. d) gravitational contraction. e) all of the above are comparable in importance. The energy emitted by the Sun is produced a) uniformly throughout the whole Sun. b) throughout the whole Sun, but more in the center than at the surface, as 1/r^2. $c) in a very small region at the very center of the Sun. d) from radioactive elements created in the Big Bang. The photosphere (the visible surface) of the Sun is like a) the surface of the Earth; you could stand on it, if you could survive the heat. b) the surface of the ocean; you couldn't stand on it, but you would clearly be able to detect differences above and below it. $c) an apparent surface; you would notice very little change as you go through it, as when you fly through a cloud. d) the surface of a trampoline; you could land on it, but the intense pressure would push you away again. Sunspots appear dark because they are a) holes in the photosphere through which you can see deeply into the stellar interior. $b) a bit cooler and thus dimmer than the rest of the photosphere. c) large opaque structures that block light from the glowing solar surface. d) causing retinal damage. Which of the following do NOT follow an 11 year cycle? a) The number of sunspots on the Sun. b) The typical latitude of sunspots on the Sun. c) The rate of solar flares. d) Incidence of strong aurora on the Earth. $e) None of the above. The chemical composition of the Sun 3 billion years ago was different from what it is now in that it had $a) more hydrogen b) more helium c) more nitrogen d) molecular hydrogen Inside a star the mass of our Sun, energy is transported from the deep interior out toward the surface by a process most like the process that a) makes a blacktop hot in the summertime b) heats the coil on an electric stove c) makes hot water boil $d) makes your hand feel heat when you put it near a candle flame The temperature in and around the Sun a) drops continuously as you move outward b) rises continuously as you move outward $c) drops as you move from the center to the photosphere, then rises above the photosphere d) drops as you move from the center to the photosphere, then rises above the photosphere Temperature decreases with elevation just outside the photosphere of the Sun. If temperature were constant with elevation in this region, then limb darkening would be _____ pronounced as it is now. a) more $b) less c) just as The light from the east limb (edge) of the Sun is blueshifted and the light from the west limb is redshifted. This is because a) different kinds of atoms emit light at the opposite edges $b) the Sun is rotating c) the distance from the Sun to the Earth changes d) the two sides of the Sun are at different temperatures The energy of a photon emitted by thermonuclear processes in the core of the Sun takes thousands or even millions of years to emerge from the surface because a) it is circling in the gravitational field of the Sun. b) it loses energy due to convection, conduction, and radiation c) of the Sun's enormous radius. $d) it is absorbed and re-emitted countless times along the way If the center of the Sun could be heated slightly, the nuclear reactions would occur faster and hence release more heat, so the Sun's core would a) collapse. $b) expand and hence cool back to its previous temperature. c) expand and hence heat up even more. d) explode. Tremendous pressure is created at the Sun's center due to its own gravity. What keeps it from collapsing? a) neutrinos and other particles generated by nuclear fusion b) a hard inner core $c) thermal (gas) pressure generated by nuclear fusion d) thermal (gas) pressure left over from the formation of the Sun