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72 Cards in this Set
- Front
- Back
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How long does it take a star to form?
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30 million years
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Open star cluster, define
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Young clusters of stars
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How can you tell if a cluster of stars is young?
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Examine its HR diagram
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If you look at a cluster of stars and you don’t see any O stars, what does that mean?
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It means the cluster is a few million years old; all the O stars have died or converted to super giants.
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Main-sequence turnoff
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???
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Globular Cluster: how many stars and how big are the clusters?
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Clusters of a million stars in a sphere 100 light-years across.
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Milky Way, how many globular clusters?
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About 160
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Globular Cluster, approximate average age
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10 billion years old
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Stars of what masses will die just like the sun?
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8 solar masses or less
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When do we probably want to get off the Earth?
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1 to 2 billion years from now because the sun’s luminosity will be great enough to boil away the oceans.
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In the core of the sun, the concentration of what has dropped?
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Hydrogen
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In the core of the sun, the concentration of what has risen?
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Helium
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Red giant, lifetime
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1 billion years
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Red giant, formation process
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(1) Hydrogen depletes in the Sun’s core, leaving helium
(2) Gravity contracts the helium, heating it (3) Helium core heats surrounding hydrogen (4) Surrounding hydrogen starts fusion, creating a fusion shell (5) As helium core contracts and contracts, fusion shell expands and expands, increasing the diameter of the sun |
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What will be the diameter of the sun when it is a red giant?
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1 AU
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Formation of red giant, change of heat of the core of the Sun
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Change from 15 million K to 100 million K.
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Magnitude system
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brightest star = 1; faintest star = 6
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A magnitude 1 star is how many times brightest than a magnitude 6 star?
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100 times
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A magnitude difference of 5 means a brightness ratio difference of what?
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100
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The apparent magnitude of a star at a distance of 10 parsecs is equal to what?
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its absolute magnitude
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Apparent magnitude (m)
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measure of how bright it is
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Absolute magnitude (M)
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how bright the star would be if it were at a distance of 10 parsecs
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The apparent magnitude, absolute magnitude, and distance of a star are all related through what formula?
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m – M = 5 log(d) – 5, where d is in parsecs
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Each of five magnitudes is a difference of
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100 in brightness.
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Hottest to Coldest spectral types
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OBAFGKM -- Oh Be A Fine Girl Kiss Me
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How can we determine the temperature of a star?
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examine its spectrum
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Coldest stars, what color?
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Red
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Hottest stars, what color?
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Blue
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What is the spectral type of sun?
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G2
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Hertzsprong-Russell Diagram (HR Diagram)
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(none)
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Spectral parallax
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To find a star's distance:
(1) Take its spectrum. (2) Classify it. (3) Thereby get its absolute visual magnitude. (4) Measure its apparent magnitude. (5) Calculate distance. |
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Relationship between luminosity, radius, and temperature
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Luminosity = (constant)(radius^2)(temperature^4)
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Spectral order, hottest to coolest
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O B A F G K M
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The Jovian Planets
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the four planets beyond the terrestrial planets
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The most massive planet in the solar system
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Jupiter
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Jupiter, mass
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more mass than all the planets combined
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Least dense planet in solar system
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Saturn
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Newtons laws, astronomical contributions
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(1) Used to predict Halley's Comet
(2) Discovered Neptune |
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Clyde Tonbaugh
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Found Pluto
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Core of Jupiter
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10 earth masses worth of rock
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Jupiter would have to have how much more mass to be a star?
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75 times more mass
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Saturn's ring, origin
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a moon disintegrated
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Total mass in asteroid belt
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less than the moon
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Number of asteroids in asteroid belt
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(1) Hundreds of thousands
(2) But only 6 are larger than 300 km in diameter |
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Why didn't asteroids form into a planet?
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Jupiter's gravity
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Kuiper Belt, characteristics
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(1) Beyond the orbit of Neptune
(2) Contains tens of thousands of icy bodies; some are comets (3) Extremely elliptic orbits (4) Orbiting out of the ecliptic plane |
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Pluto, classification
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Dwarf planet, part of the Kuiper Belt
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Oort Cloud, distance from Sun
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50,000 AU
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Oort Cloud, composition
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Ice, rock: comets
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Comet, tail size
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Up to 100,000 km
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Comet, tail explanation
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solar wind blows away sublimated ice. That said, a comet does not necessarily move in the opposite direction of the Sun.
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Hally’s comet is an example of what kind of comet?
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periodic
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Oort Cloud, mass
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1 to 10 Earth masses
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Meteor shower, explanation
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when the Earth intersects the orbiting debris (comet steram) of a comet
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Meteor shower, size of particles
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could be as small as a grain of sand. Because the particles move so fast, they still lighten when smashing into the atmosphere.
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Yucatan Peninsula crater, dimensions
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180 x 300 km crater
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p
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Half of the position shift (arc seconds) a star exhibits after 6 months due to parallax (measured in arc-seconds)
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Relationship between distance and p
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d = 1/p
d = distance in parsecs p is in arc-seconds |
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Torino Scale
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An 11-point scale (includes 0) for rating the severity of an asteroid threat.
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Torino Scale - categories
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0: no hazard
1: normal 2-4: meriting attention by astronomers 5-7: threatening 8-10: certain collisions |
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Apophis, characteristics
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(1) Pass within 30,000 km of Earth in 2029
(2) Diameter: 300 m (3) Asteroids this big pass Earth about once every thousand years (4) Subsequent orbit may bring it even closer to Earth in following years |
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Sun's lifetime equation
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Sun’s lifetime = (Sun’s mass)(Energy per burnt mass)/(Luminosity)
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Solar system, age
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4.6 billion years
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If powered by coal, how long would the Sun last?
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5,000 years
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How much hydrogen mass is lost to energy?
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.7%
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Fusion, process
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4 H protons fuse into one He nucleus
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Fusion, products
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(1) 1 He nuclear
(2) Energy (3) Neutrinos |
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Sun, expected lifetime
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10 billion years
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Sun granule, explain
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(1) The bright granule is caused by rising currents of hot gas
(2) The "cracks" between granules is sinking currents of cooler gas |
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Maunder Minimum
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A period of time (1645–1717) in which sunspots were rarely observed.
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Distance increases by 10 times, magnitude decreases by what?
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5 times
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How long does it take a photon to get out of the sun?
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100,000 years
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