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How big is the total mass in the asteroild belt?
10% the Lunar Mass
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What is the source of some additional comets?
The Kuniper Belt
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Planets going around other things than the Sun
Extrasolar Planets
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Describe the Theory of star formation.
- Raw material in Interstellar clouds
- Cloud collisions cause compression
- Gravitational collapse
- Faster rotation leads to flattening of outer region into disk
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Describe the Theory of Planet formation.
- Accretion- rear end collisions increase dust grain size
- Larger grains grow faster
- Result: A planet with leftover debris
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What are some Planet discovery techniques?
- Doppler Shift of star's "wobble"
- Transits of planet across star
- Selection effects
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Describe the Stellar Interior Models.
- Interior cannot be observed directly
- Models start with specified mass and chemical composition
- Calculate resultion surface temp., luminosity, and radius
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Name the 5 physical principles.
1. pressure v.s. gravity balance
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Io, despite its relatiely small size, has a crust which erupts with sulfur-rich lava and geysers. Why?
This moon is flexed by tidal forces from Jupiter and Europa
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Descending below Jupiter's clouds and deep into its atmosphere, we would enter into what kind of region?
An ocean of liquid hydrogen
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In the balance between pressure and gravity in a star, what must the pressure do?
Push outward with a force equal to the weight of the overlying layers
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What property of the Sun is numerically smaller than the corresponding value for the Earth?
Average Density
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In the second step of the fundamental nuclear reactions in the Sun, what is produced when a deuterium nucleus and a proton fuse?
A helium isotope and a gamma ray
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EInstein's equation for the conversion of mass into energy involves what fundamental constant?
The vacuum speed of light
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Why are high temperatures required for nuclear fusion reactions?
To overcome the electrical repulsion of the nuclei
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Approximate planetary spacing regularity which matches Uranus and the asteroid belu
Bode's Law
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What are the surface layers of comets heated by?
Sunlight releasing gases and solid grains into coma
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Describe the tail of a comet.
- Points away from the sun
- Ionized gas portion pushed by solar wind
- Dust grain portion by radiation pressure of reflected sunlight
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What is the discovery of the periodicity of Halley's Comet supported by?
The application of Kepler's Laws to things other than planets
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Asteroid fragments and comet debris with the potential to collide with earth
Meteroids
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The glowing trail of atmospheric gases, heated by the passage of a meteroid
Meteor
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The pieces which survive atmospheric friction and hit the earth's surface
Meteorites
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When do meteor showers occur?
When the earth crosses the orbit of a decaying comet
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Why are there no meteorite showers?
COmet debris generally do not survive the atmospheric friction
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What are some characteristics of Planetary orbits?
- common plane and direction
- low eccentricity
- rotation shows similar order
- moons have similar motions
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What do Terrestrial and Jovian planets have in common?
size and composition
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Describe the Solar System origin.
- collapse of an interstellar cloud
- cloud contracts, rotates faster, outer parts flatten into a disk
- as disk cools, solid grains form, forming planets
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What causes the annual parallax shift?
the earth's orbital motion (inversely proportional to distance)
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Other than parallax, how else can you observe stars?
Apparent brighness of stars (brightness fades B~1/d2)
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A measure of the Doppler Shift, tells the the larger the shift, the higher the velocity (works at any distance)
Radial Velocity
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Requires both the angular rate of change and the distance (works only for nearby stars)
Transverse Velocity
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Describe the solar motion of Vega.
About 20 km/s toward Vega-ewuivalent to 4 AU/yr
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What is the goal of stellar luminosity?
To measure energy recieved and then allow for the distance to get the total power emitted
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How is the energy recieved from luminosity measured?
on the apparent magnitude scale; 1-brightest--6-faintest
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Describe the HR Diagram.
- Vertical axis- Luminosity
- Horizontal axis- Temperature (backwards)
- main sequence, giants, supergiants, whitedwarfs
- star sequence from high-low temp. O B A F G K M
- Lower main sequence stars are most common
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How can the radius of some nearby large stars be found?
direct measurement of angular size and distance
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The unresolved systems seen "edge on"; the time required for it determines the relative sizes of the two stars
Eclipsing Binaries
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If _____ and _____ are known, a good radius estimate can be calculated
luminosity and temperature
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Describe the stars range in the HR Diagram.
- Main Sequence-0.1-10x Sun
- Giants/Supergiants- 100x Solar
- White Dwarfs- only 1/100 sun's size=earth's radius
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Those where both star images are resolved; measured by seperation and period
Visual Binaries
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Unresolved systems with a spectrum that shows two sets of oppositely Doppler shifted spectral lines
Spectroscopic Binaries
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Describe the masses of Binary stars.
- most masses range from .07 to 100 times the sun
- Lower end of range set by core temperature required for nuclear power source
- upper end set by short lifetime and instability
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Describe the range of temperatures and densities of Interstellar matter.
- cold and dense with H2 molecules
- hot and thin with H+ ions
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What is the evidence of interstellar gas?
- emission nebulae
- interstellar absorption lines
- radiowavelength spectral lines (espically at 21-cm from H)
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What is the evidence for interstellar dust?
- dark nebulae
- reflection nebulae
- interstellar reddening
- infared emission
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What conditions are needed for new stars?
Cold, massive, dense, molecular clouds
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How much of the gravitational energy release is retained to heal the prostar?
50%
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More massive stars take less time; low mass stars take longer; at a core temperature of 10 million K, what happens?
Fusion begins and the star readjusts to a stable "main sequence" state
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