Chapter 11: Our Star Flashcards
gravitational equilibrium
energy supplied by fusion maintains the pressure that balances the inward crush of gravity
energy balance
the rate at which energy radiated from the surface of the sun must be the same as the rate at which it is released by fusion in the core
gravitational contraction
the process in which gravity causes an object to contract, thereby converting gravitational potential energy into thermal energy
when provided the energy that heated the core as the sun was forming
contraction stopped when fusion began
sun’s radius
6.9 x 10^8 m (109 times the earth)
sun’s mass
2 x 10^30 kg (300,000 times the earth)
sun luminosity
3.8 x 10^26 watts
solar wind
a flow of charged particles from the surface of the sun
corona
outermost layer of solar atmosphere (around 1 million K)
chromosphere
middle layer of solar atmosphere (around 100,000-1,000,000 K)
photosphere
visible surface of Sun (around 6000 K)
convection zone
energy transported upward by rising hot gas
radiation zone
energy transported upwards by photons
core
energy is generated by nuclear fusion of hydrogen into helium (around 15 million K)
fission
big nucleus splits into smaller pieces (ex: nuclear power plants)
fusion
small nuclei stick together, making a bigger one (ex: the sun, stars)
solar thermostat
the regulation of the sun’s core temperature that comes when the sun is in both energy balance and gravitational equilibrium
decline in core temp causes fusion rate to drop so…
core contracts and heats up
rise in core temp causes fusion rate to rise so…
core expands and cools down
solar neutrino problem
disagreement between the predicted and observed neutrinos coming from the sun
why does the sun emit neutrinos
fusion in the suns core create neutrinos when protons turn into neutrons
facts about timeline of solar neutrino problem
-early searches failed to find predicted number
-recent observations find the right number neutrinos but some have changed form
sunspots
blotches on the sun that appear darker than surrounding regions
- cooler than other parts of suns surface
-regions with strong magnetic fields
satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum….
because Earth’s atmosphere tends to expand during solar maximum exerting more drag on satellites in low orbits
solar flares
huge and sudden release of energy on the solar surface, probably caused when energy stored in magnetic fields is suddenly released
what are solar flares caused by?
magnetic activity
what do solar flares send into space?
bursts of x-rays and charged particles
coronal mass ejections
bursts of energetic charged particles from the sun’s corona out through the solar system
how can we best observe the sun’s chromosphere and corona?
-the chromosphere is best observed with ultraviolet telescopes
-corona best observed with x-ray telescopes
what determines the total amount of incoming sunlight?
a planet’s distance from the sun
what affects the temp differences of day and night?
rotation rate
reflectivity (albedo)
fraction of incoming sunlight it reflects
- low albedo planets absorb more sunlight leading to hotter temps
planet with highest average surface temp
venus, because its dense carbon dioxide atmosphere
Venus temp without greenhouse effect
510 degrees Celsius colder
Earth temp without greenhouse effect
31 degrees Celsius colder
What would happen is the Earth was more reflective?
temp would go down
What would happen is the Earth did not have an atmosphere?
temp would go down more than 10 degrees Celsius
Ionization
removal of an electron
Dissociation
destruction of a molecule
scattering
change in photon’s direction
absorption
photon’s energy is absorbed
What can ionize and dissociate molecules?
x-rays and UV light
what do molecules scatter more, blue or red light?
blue light
what light can molecules absorb?
infrared light
troposphere
lowest layer of Earth’s atmosphere
- temp drops with altitude
- warmed by infrared light from surface and convection
convection
process in which warm materials expand and rise while cool material contract and fall
stratosphere
layer above the troposphere
- temp rises with altitude in lower part, drops with altitude in upper part
- warmed by absorption of ultraviolet sunlight
thermosphere
layer at about 100 km altitude
-temp rises with altitude
-x-rays and ultraviolet light from sun heat and ionize gases
exosphere
highest layer in which atmosphere gradually fades into space
- temp rises with altitude, atoms can escape into space
- warmed by x-rays and UV light
why is the sky blue?
air molecules scatter blue light more than red light
why are sunsets red?
red light scatters less
why is earth the only planet with a stratosphere?
UV absorbing ozone molecules
- protect us from sun’s UV light
what do magnetic fields of Earth’s atmosphere do?
protect us from charged particles streaming from the sun
aurora
glow of charged particles from solar wind energizing upper atmosphere near magnetic poles
what is the sun made of (by mass)
70% hydrogen, 28% helium, 2% other elements
