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34 Cards in this Set

  • Front
  • Back
Sun distance from Earth
- 1 AU
- 93 Million miles
- 8 1/3 lightminutes
Radius of the Sun
- 109 Earth Radii
- 700,000 km
- 1 solar radius
Mass of our Sun
- 333,400 Earth Masses
- 1 solar mass
Luminosity of the Sun
- 4 trillion trillion, 100 watt lightbulbs, every 6 months
- 1 solar luminosity
Age of the Sun and expected lifetime?
- 4.6 Billion years
- 10 billion years
Rotation period of Sun
@ equator = 25 days
6 Layers of the Sun
Radiative Zone
Convective Zone
- 40% of sun's mass
- 15 million K (hottest)
- extremely high pressure, really tightly packed
- 59% of sun's mass
- 4 million K (2nd hottest)
- very high density/pressure (atoms very packed and crowded)
- radiative transport is how energy transports
- less than 1% of sun's mass
- 1 million K
- low pressure
- negligible amount of mass
- 5800 K (very cool compared to other layers)
- low pressure/density
- too bright, so it covers the other lays past it
- visible surface of the sun
- hot, thin gas
- virtually all the visible light comes from photosphere
- negligible amount of mass
- 10,000 K, warmer as we get farther out in layers
- very low pressure
- rarely seen in visible light
- negligible amount of mass
- 1-2 million K, much hotter than 2 previous layers before
- very low pressure/density
- rarely seen in visible light, much dimmer than the photosphere
Radiative Transport
1. an atom temporarily absorbs a photon
2. photon is then emitted in a random direction then absorbed again
3. repeat above steps
4. "random walk" ... drunkards walk

** avg. travel time is a million years
Composition of the Sun
Hydrogen (92%)
Helium (7.8%)
Oxygen (.06%)
Carbon (.03%)

67 different elements in TOTAL
Metal Content
Metal Content in the sun is .2%, because

99.8% of all atoms in the Sun are Hydrogen and Helium
Energy Transport of atoms on photosphere
Low Pressure - atoms are mobile
Convection transport
(cells are huge bubbles of gas)
Hot cells rise, cool cells fall.
Cool cell at bottom absorbs the photons of energy and when it becomes hot rises back to the top
Then - energy is released and it falls back again.
Proof of Convection
We see granules on the photosphere
- avg. size = 700-1000km
- 4 million granules on photosphere
- Using Wien's law, we know bright cells are hotter and dark cells are cooler
Doppler Shift
- hot cells are 'blueshifted', towards Earth
- cool cells are 'redshifted', away from Earth

*tells you about the speed of motion
- avg. speed = 1 km/sec
Blueshift vs. Redshift
Doppler effect

- Blue, towards earth
- Red, away from earth
The Corona (more details!)
- the outermost layer, it's the solar atmosphere
- over 1 million degrees
- vrey low pressure, so the atoms are really spread out
- it can only be studied during a total solar eclipse
Coronal Holes
almost black spots on the Sun when you look at an xray picture
- always seem to change in size and shape
Solar Wind
very fast moving stream of protons and electrons, escapes through the coronal holes and interacts with the Earth's magnetic fields ... how we get the Aurora Borealis
Solar flare
represents an explosion of gas from the sun's photosphere that also escapes into space
What is a sunspot?
A dark, magnetic disturbance on the surface of the sun (photosphere), that is much cooler leading to their dark color. Actually very bright orange, but appear dark in contrast to the rest of the sun

- they are the size of earth
- avg. lifetime is a few hours to a few months
What does sunspot movement prove??
1. solar rotation
2. differential rotation
- every latitude on the sun rotates at a different speed, and is fastest at the equator
- is therefore, a gaseous object
# of sunspots we see versus time
- the # changes with time (its not a constant)
- it increases/decreases periodically and cyclically
- 11 years is the avg time from sunspot max to sunspot min
- there are some variations though
Variatons with the sunspots
- not always 11 yrs between maxiumums
- # at maximum is not always the same
- 1645 to 1715 there were virtually no sunspots (Maunder Minimum)
What is the Maunder Minimum?
a time when the suns brightness dropped and we don't really know why. There were virtually no sunspots and it was like a little ice age
What do you know about sunspots?
- they always come in pairs
- the pairs have magnetic polarity (North/South)
- sun's magnetic poles flip every 11 yrs
- discovered by galileo
What is nuclear fusion?
a process of energy generation by the combination of lighter elements into heavier elements (ex. hydrogen into helium), also the collision of protons to create a heavier element

can only occur in the CORE
What are the 2 necessary conditions for nuclear fusion?
1. extremely high temperature, which results from high speeds so the protons can overcome that they repel eachother

2. extremely high pressure so that many collisions can occur all the time
Net Fusion Reaction for 4 Hydrogen Atoms
1 Helium atom + 2 positrons + 2 neutrinos + energy

**ends up being "missing mass" of 0.7% ... the missing mass is converted into energy
E = mc2
amount of potential energy = mass of object x speed of light squared

*this implies that a relatively small amount of mass represents a huge amount of mass-energy