Chapter 16 Flashcards
(44 cards)
composition of the sun by mass
74% H, 25% He, 1% other
temperature of the surface of the sun
5800K
luminosity
3.9x10^26 watts
Kelvin-Helmhotz contraction
compression of gas by gravity
proposed as a source of the sun’s heat in the mid 1800’s
hydrogen fusion
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
Sun’s fusion rate
6 x 10^11 kg of Hydrogen per second
hydrostatic equilibrium
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
thermal equilibrium
sun is radiating the same amount of energy as it is producing per unit time
heat transfer in the sun
mostly convection and radiative diffusion
sun is not dense enough to be an effective conductor
density of the sun
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
ratiative zone
center of the sun to .71 R
energy is transported by radiative diffusion
convective zone
.71 R - 1 R
temperature cools enough to form hydrogen atoms which then absorb photons.
energy transfer rate
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
helioseismology
technique of measuring the vibration of the sun as a whole
vibrations in the sun
sun oscillates in millions of modes
in one such mode patches of the sun’s surface oscillate about 10m every 5 minutes
solar neutreino problem
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
photosphere
lowest layer of the sun’s atmosphere
thin layer of gas which produces nearly all of the sun’s visible light
layers of sun’s atmosphere
photosphere (“sphere of light”), chromosphere “sphere of color,” and corona
contain mostly plasma
sun’s absorption lines
are formed by the atmosphere above the lower photosphere where atoms absorb emitted photons
sun’s absorption lines
are formed by the atmosphere above the lower photosphere where atoms absorb emitted photons
granulation
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
supergranule
a longer lasting (1 ish day) and much larger (35,000 km) convection cell which may contain a hundred or more granules.
density and composition of photosphere
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
temperature of the chromosphere
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
