Chapter 16

Question 1

composition of the sun by mass

Answer 1

74% H, 25% He, 1% other

Question 2

temperature of the surface of the sun

Answer 2

5800K

Question 3

luminosity

Answer 3

3.9x10^26 watts

Question 4

Kelvin-Helmhotz contraction

Answer 4

compression of gas by gravity

proposed as a source of the sun’s heat in the mid 1800’s

Question 5

hydrogen fusion

Answer 5

form of thermonuclear fusion and source of energy for the sun

4 H → 4He + energy (.07% of initial mass)

2 H → 2H + neutrino + positron
2H + H → 3He + gamma-ray photon
2 3He → 4He + 2 H
positron + electron → 2 gamma-ray photons

Question 6

Sun’s fusion rate

Answer 6

6 x 10^11 kg of Hydrogen per second

Question 7

hydrostatic equilibrium

Answer 7

pressure increases deeper into the interior of a star

outward force is produced by the nuclear fusion in the sun’s core, inward force is produced by gravity

Question 8

thermal equilibrium

Answer 8

sun is radiating the same amount of energy as it is producing per unit time

Question 9

heat transfer in the sun

Answer 9

mostly convection and radiative diffusion

sun is not dense enough to be an effective conductor

Question 10

density of the sun

Answer 10

all the sun’s energy/luminosity is produced in its inner 25 R

94% of the sun’s mass is within .5 R

density is quarter of that of the core by .25 R

Question 11

ratiative zone

Answer 11

center of the sun to .71 R

energy is transported by radiative diffusion

Question 12

convective zone

Answer 12

.71 R - 1 R

temperature cools enough to form hydrogen atoms which then absorb photons.

Question 13

energy transfer rate

Answer 13

170,000 years for energy produced at the sun’s core to leave the sun’s surface

photon travel slowed by density of the inner sun

Question 14

helioseismology

Answer 14

technique of measuring the vibration of the sun as a whole

Question 15

vibrations in the sun

Answer 15

sun oscillates in millions of modes

in one such mode patches of the sun’s surface oscillate about 10m every 5 minutes

Question 16

solar neutreino problem

Answer 16

for much of the 20th century scientist were only able to detect a fraction of the number of neutrinos expected from the sun.

neutrino oscillation explains this discrepancy – there are 3 types of neutrinos and neutrino’s commonly oscillates between these types

Question 17

photosphere

Answer 17

lowest layer of the sun’s atmosphere

thin layer of gas which produces nearly all of the sun’s visible light

Question 18

layers of sun’s atmosphere

Answer 18

photosphere (“sphere of light”), chromosphere “sphere of color,” and corona

contain mostly plasma

Question 19

sun’s absorption lines

Answer 19

are formed by the atmosphere above the lower photosphere where atoms absorb emitted photons

Question 20

sun’s absorption lines

Answer 20

are formed by the atmosphere above the lower photosphere where atoms absorb emitted photons

Question 21

granulation

Answer 21

the blotchy pattern observed in the photosphere caused by convection cells on average 1000km across which form, disappear, and reform in minutes

the temperature difference between the center and the edge of the cell is around 300 K

Question 22

supergranule

Answer 22

a longer lasting (1 ish day) and much larger (35,000 km) convection cell which may contain a hundred or more granules.

Question 23

density and composition of photosphere

Answer 23

density is about .01% of Earth’s atmosphere at sea level

mostly H and He; contains negative hydrogen ions which make the photosphere very opaque and an excellent blackbody

Question 24

temperature of the chromosphere

Answer 24

temperature increases dramatically further from the photosphere in the chromosphere

top of photosphere: 4400 K
top of chromosphere: 25000 K

spectrum dominated by emission lines

Question 25

chromosphere density and composition

Answer 25

a thousandth the density of the photosphere or 10^-8 that of Earth’s atmosphere

about 2000 km thick

H, ionized He, traces of ionized Ca

Question 26

spicules

Answer 26

rising jets of gas through the chromosphere forming a peak in the corona

rise at about 20 km/s and last about 15 minutes

at any moment around 300,000 are present

Question 27

corona

Answer 27

several million km thick but nearly a vacuum

suddenly around 2,000,000 K or twice the temperature of the chromosphere; increases in temperature further from the sun

Question 28

corona composition

Answer 28

highly ionized atoms

Question 29

solar wind

Answer 29

outflow of gas from the corona containing mostly electrons and ionized H and He

about a million tons (10^9 kg) per second

Question 30

coronal hole

Answer 30

a thinner, lower temperature region of the corona from which most of the solar wind escapes

Question 31

sunspots

Answer 31

low temperature areas on the photosphere (4300 K) caused by intense magnetic fields

are often the size of the Earth and can be large enough to view without a telescope

offten appear in groups

Question 32

differential rotation

Answer 32

when the equatorial regious of a gassious body (like our sun) rotate faster than the polar regions

rotation of the sun at the equator: 25 days
rotation of the sun at the poles: 35 days

Question 33

sunspot cycle

Answer 33

cycle of sunspot maximums and sunspot minimums

period of about 11 years

Question 34

solar cycle

Answer 34

cycle of 22 years during which the sun’s magnetic field “flips” twice

Question 35

Zeeman effect

Answer 35

the splitting of spectral lines by an intense magnetic field

Question 36

magnetic-dynamo model

Answer 36

differential rotation causes the sun’s magnetic field to “wrap” around itself; convection in the photosphere causes “wrinkles” in the magnetic field

sunspots are the result of the magnetic field coming through the photosphere

Question 37

sunspot group

Answer 37

sunspots form travel in groups

“proceeding members” at the front edge of motion and “following member” further back

Question 38

space weather

Answer 38

variations in the solar wind which can effect satellites and astronauts

Question 39

magnetic reconnection

Answer 39

the magnetic rearrangement of two arches in close proximity

releases a tremendous amount of energy into the sun’s atmosphere heating the chromosphere and corona

Question 40

magnetic field lines in plasma

Answer 40

field lines move the ionized particles in the plasma causing the magnetic field to follow the motion of the particles in convection

Question 41

plage

Answer 41

bright, hot region of the chromosphere which form just before a new sunspot

Question 42

filaments

Answer 42

dense, cool lines in the chromosphere caused by magnetic field lines

form prominences, bright arching columns of gas

Question 43

solar flare

Answer 43

vast ejection of particles and radiation into space caused by magnetic reconnection around a sunspot group

energy comes directly from the magnetic disturbance, not thermonuclear fusion

Question 44

coronal mass ejections

Answer 44

a massive eruption of coronal gas far beyond the sun’s atmosphere

some of the mass falls back to the sun while some is ejected at high speed