Term
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Definition
How bright a star appears- affected by its distance from us
-closer stars=larger apparent brightness
-apparent brightness decreases according to distance^2
**Distance and luminosity |
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Definition
total amount of light the sun emits in all directions [watts]
- greater luminosity=greater apparent brightness |
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| Inverse square law for light |
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Definition
Specifies the relationship between apparent brightness, distance, and luminosity
b= L/4piD^2
b=apparent brightness
d=distance
L=luminosity |
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Term
| If 2 stars are the same distance away, the star with a higher luminosity will have a _____________ apparent brightness |
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Definition
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| If two stars have the same luminosity, the star with the _______ distance will have a larger apparent brightness |
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Definition
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| Why does the apparent brightness of a star not tell us the distance? |
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Definition
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Definition
| small shift in the sky that is caused by Earth's orbital motion |
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| A star that has a smaller distance from from us wil have a _______ stellar parallax |
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Definition
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Term
| Formula of relationship between a stars parallax and its distance |
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Definition
d= 1arcsec*pc/p
d=distance to the star
p=stellar parallax of star |
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Term
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Definition
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| Can only use stellar parallax method to determine the distances of stars within _____pc because if they are farther away their parallaxes are too small to detect |
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Definition
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| What holds an atom together |
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Definition
| The opposing charges of the protons and neutrons |
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Term
| Short wavelength of light has _____ of energy |
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Definition
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Term
| The amount of energy that an electron loses determines the __________ of light emitted |
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Definition
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Term
| If the North Star moves 2x closer how does its luminosity change? |
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Definition
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Term
| If the north star moves 2x closer, how will its apparent brightness change? |
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Definition
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Term
| What causes a star to have a certain luminosity? |
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Definition
| distance away from us and its apparent brightness |
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Term
| What part of an atom has most of the mass? |
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Definition
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Term
| What causes specific spectra? |
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Definition
| Different combinations of temperature and density |
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Term
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Definition
Emitted by an object that is hot and low density -> see through it
-Dark with some visible wavelengths of light
- only see specific wavelengths |
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Term
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Definition
-emitted by an object that is hot and high density
-see everything |
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Term
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Definition
an object that emits a continuous spectrum
-emits all wavelengths of light because atoms in the object are so crowded that they affect how nearby atoms emit and absorb light |
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Term
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Definition
2 conditions must be met:
1. must be a blackbody emitting a continuous spectrum
2. blackbody's light must pass through a cooler, low density material
-the cooler, low density material absorbs some of the light passing through it, so the light that we observe is missing some wavelengths
-see continuous spectrum with specific wavelengths missing
Light--> cool gas--> absorption spectrum |
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Term
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Definition
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Term
| Can you determine the composition of an object if it emits a continuous spectrum? |
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Definition
| NO, there are no spectral lines |
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Term
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Definition
| 73% hydrogen, 25% helium, 2% heavier elements |
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Term
| Why are the sun and the stars different colors? |
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Definition
| Stars are all made of the same material - not based on composition |
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Term
| Is a red star hot or cool? |
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Definition
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Term
| If a star's surface temperature is large, then each part of the star emits ______ light, so its luminosity is _________ |
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Definition
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Term
| If two stars have the same surface temp, then the star's ________ determines luminosity |
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Definition
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Term
| Which is more luminous, a red star, or a blue star? |
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Definition
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Term
| If two stars have the same parallax what else is true? |
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Definition
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Term
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Definition
Calculate a star's surface temperature
T= 2.9 * 10^6 knm/max wavelength |
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Term
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Definition
Calculate star's radius
L=4piR^2constantT^4 |
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Term
| If 2 stars have the same radius, but one star has 2x the surface temp of the other star, then the hotter star will have _____ x the luminosity |
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Definition
| 2^4 = 16x ... stefan-boltzmann law |
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Term
| if two stars have the same surface temp, but one star has 2x the radius of the other then the bigger star will have _____x the luminosity |
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Definition
| 2^2= 4 ... stephan-boltzmann law |
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Term
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Definition
| extremely small radii and low surface temp and dim |
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Term
| Echo and Foxtrot have same luminosity. Echo's surface temp is 5x larger than Foxtrots. How do their radii compare? |
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Definition
| Foxtrots's radius is 25x larger than echos sqrt (5^4) =25 |
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Term
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Definition
| Star's velocity through the sky across our line of sight |
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Term
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Definition
| a star's velocity directly toward or away from us |
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Term
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Definition
a change in the wavelength of a light wave caused by the motion of the emitting object or the observer
-the star's radial velocity affects the light we receive from it through doppler effect
-stars motion toward or away from the earth affects the light we receive |
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Term
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Definition
| object moving away (towards red end of spectrum) Increased wavelength |
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Term
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Definition
| object moving towards us (closer to blue end of spectrum) decreased wavelength |
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Term
| Use doppler effect to determine ___________ |
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Definition
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Term
| The bigger the shift of the absorption spectrum, the ______ the velocity |
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Definition
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Term
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Definition
2 nuclei combine to form one heavier nucleus
-Only happens when two protons are moving so quickly that they fuse before they can repel each other |
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Term
| Which gas can fuse at lowest temperatures |
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Definition
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Term
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Definition
sequence of fusion reactions that happens in the sun's core
-4 hydrogen nuclei (protons) are needed at the beginning of the chain of reactions
-some mass is released as radiative energy
-4 hydrogen=1 helium |
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Term
| Why does the sun's core have the necessary conditions for fusion? |
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Definition
- core temp is hot
-core is highly dense= protons are close together |
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Term
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Definition
sub-atomic particles that have no charge and very tiny masses
-pass directly through solid matter
-leave sun during proton-proton chain |
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Term
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Definition
| the study of vibrations in the sun |
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Term
| What can the sun's vibrations tell us about the sun? |
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Definition
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Term
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Definition
-makes up 25% of suns radius
-hottest
-densest |
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Term
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Definition
-50% of sun's radius
-dense enough that light can't travel in a straight line, bounces from particle to particle = can take a wave of light 100,000 years to travel through the radiation zone |
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Definition
25% of suns radius
-heated by light from radiation zone=gas has convection |
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Definition
top of the convection zone
=visible surface of the sun |
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Term
| can we use helioseismology to study other stars? |
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Definition
| no, they are too far away to see vibrations |
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