10 Key Ideas

Question 1

The sun’s atmosphere

Answer 1

the thin shell of the sun’s gases we see are from its photosphere, the lowest level of its atmosphere. the gases in this layer shine nearly like a blackbody. the photosphere’s base is at the top of the convective zone

Question 2

the convective zone

Answer 2

convection of gas below the photosphere produces features called granules

Question 3

the chromosphere

Answer 3

above the photosphere is a layer of hotter but less dense gas called the chromosphere. jets of gas called spicules rise up into the chromosphere along the boundaries of supergranules.

Question 4

the corona

Answer 4

the outermost layer of thin gases in the solar atmosphere, called the corona, extends outward to become the solar wind at great distances from the sun. the gases of the corona are very hot, but they have extremely low densities

Question 5

the active sun

Answer 5

some surface features on the sun vary periodically in an 11 year cycle. the magnetic fields that cause these changes actually vary over a 22 year cycle

Question 6

sunspots

Answer 6

sunspots are relatively cool regions produced by local concentrations of the sun’s magnetic field protruding through the photosphere. the average number of sunspots and their average latitude vary in an 11 year cycle

Question 7

solar activity

Answer 7

a prominence is gas lifted into the sun’s corona by magnetic fields. a solar flare is a brief but violent eruption of hot ionized gases from a sunspot group. Coronal mass ejections and flares that head our way affect satellites, communication, and electric power, and cause aurorae.

Question 8

the magnetic dynamo model

Answer 8

the magnetic dynamo model suggests that many transient features of the solar cycle are caused by the effects of differential rotation and convection on the sun’s magnetic field

Question 9

the sun’s interior

Answer 9

the sun’s energy is produced by the thermonuclear process, called hydrogen fusion, in which four hydrogen nuclei release energy when they fuse to produce a single helium nucleus.

Question 10

einstein’s equation

Answer 10

the energy released in a thermonuclear reaction comes from the conversion of matter into energy as described by E=mc^2

Question 11

the solar model

Answer 11

the solar model is a theoretical description of the sun’s interior derived from calculations based on the laws of physics. the solar model reveals that hydrogen fusion occurs in a core that extends from the center to about a quarter of the sun’s visible radius

Question 12

radiative diffusion

Answer 12

in the sun’s outer layers, energy is transported to the sun’s surface by convection

Question 13

neutrinos

Answer 13

neutrinos were originally believed to be massless. the electron neutrinos generated and emitted by the sun were originally detected at a lower rate than is predicted by our model of thermonuclear fusion. the discrepancy occurred because electron neutrinos have mass which causes many of them to change into other forms of neutrinos before they reach earth

Question 14

what percentage of the solar system’s mass is the sun?

Answer 14

the sun contains about 99.85% of the solar system’s mass

Question 15

does the sun have a solid and liquid interior like earth?

Answer 15

no the entire sun is composed of hot gases

Question 16

what is the surface of the sun like?

Answer 16

the sun has no solid surface. it has no solids or liquids anywhere, the level we see, the photosphere, is composed of hot churning gases

Question 17

does the sun rotate?

Answer 17

the sun’s surface rotates differentially, varying between once every 35 days near its poles and once every 25 days at its equator

Question 18

what makes the sun shine?

Answer 18

thermonuclear fusion in the sun’s core is the source of the sun’s energy

Question 19

are matter and energy conserved?

Answer 19

by themselves, they are not always conserved. nuclear fusion converts matter into energy. energy can also be converted into matter. the sum of the matter (multiplied by c^2) and energy is always conserved