Chapter 14 Flashcards
(28 cards)
Is the sun on fire?
No, it would’ve only lasted 10k years
Is the sun contracting?
No, it would have only lasted 25 million years
Why does the Sun shine?
The Sun shines because gravitational equilibrium keeps its core hot and dense enough to release energy through nuclear
fusion.
Gravitational equilibrium
Energy supplied by fusion maintains the pressure that balances the inward crush
of gravity.
Energy Balance
The rate at which energy radiates from the surface of the Sun must be the same as the rate at which it
is released by fusion in the core.
Whats the Sun’s radius?
6.9 x 10^8m
109 times Earth
Whats the Sun’s mass
2 x 10^20 kg
300,000 Earths
What’s the Sun’s luminosity
3.8x10^26 watts
Solar Wind
A flow of charged particles from the surface of the Sun
Corona
Outermost layer of solar atmosphere ~ 1 million K
Chromosphere
Middle layer of solar atmosphere
Photosphere
Visible surface of Sun ~ 6000 K
Convection Zone
Energy transported upward by rising hot gas
Radiation Zone
Energy transported upward by photons
Core
Energy generated by nuclear fusion ~ 15 million K
Nuclear Fission
Big nucleus splits into smaller pieces.
(Example: nuclear power plants)
Nuclear Fusion
Small nuclei stick together to make a bigger one.
(Example: the Sun, stars)
How Does Nuclear Fusion Occur in the Sun?
High temperatures enable
nuclear fusion to happen in the
core.
The Sun releases energy by fusing four hydrogen nuclei into one helium nucleus.
What would happen inside the Sun if a slight rise in core temperature led to a rapid rise in
fusion energy?
The core would expand and cool.
Solar Thermostat
Decline in core temperature causes fusion rate to drop, so core contracts and heats up.
Rise in core temperature causes fusion rate to rise, so core expands and cools down.
How Does the Energy from Fusion Get out of the Sun?
Energy gradually leaks out of radiation zone in form of randomly bouncing photons.
Convection (rising hot gas) takes energy to surface.
How We Know What Is Happening Inside the Sun?
We learn about the inside of the Sun by making mathematical models observing solar vibrations
observing solar neutrinos.
Patterns of vibration on the surface tell us about what the Sun is like inside. Here, vibrations revealed by Doppler shifts are
shown
Solar Neutrino Problem
Early searches for solar neutrinos failed to find the predicted number.
More recent observations find the right number of neutrinos, but some have changed form.
Solar Activity
Sunspots
Solar flares
Solar prominence
All these phenomena are related to magnetic fields.
