ASTR 101: EXAM 2
65 Cards in this Set
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What produces a continuous spectrum
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a solid, liquid, or dense gas excited to emit light will radiate at all
wavelengths
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what produces an emission line spectrum
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a low-density gas excited to emit light will do so at specific wavelengths
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what produces an absorption spectrum
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if light comprising a continuous spectrum passes through a cool, low density gas
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terrestrial planets
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Mercury, Venus, Earth, Mars.
-rocky. relatively thin atmospheres. some live volcanoes or evidence of past lava flows. few moons
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Jovian planets
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Jupiter, Saturn, Uranus, Neptune
-gas giants. low average density compared to terrestrial. all have rings. all have many moons
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the carbon dioxide cycle
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this cycle acts a thermostat for the Earth, because the rate at which carbon dioxide is extracted from the atmosphere is very sensitive to temperature. a small change in the earth’s atmosphere can be offset by a change in the carbon dioxide cycle
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principal greenhouse gases
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CO2 : carbon dioxide
CH4 : methane
N2O : nitrous oxide
H2O : water vapor
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what is a comet nucleus made of
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rocks and gravel frozen together with ice
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what is a comet tail made of
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ice boils off, leaving gas + dust tail
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what are meteors
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piece sof sand that vaporizes in earths atmosphere due to friction
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what is the titus-bode law
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rough rule that predicts the spacing of the planets in the solar system. lead Bode to predict the asteroid belt situated between Mars and Jupiter
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what is dwarf planet
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doesn't meet rules for planet
orbits a star
be large enough to be round
clear out most objects form your orbital path
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destructive power of a collision with an asteroid or comet nucleus comes from the kinetic energy of the object hitting the earth
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kinetic energy is ½ mv2 so it increase rapidly with the velocity of the impact
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what are the three most abundant elements in the earths crust
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oxygen, silicon, aluminum
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what is the Kuiper belt
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extends from the orbit of Neptune (30 AU) out to roughly 55 AU. It consists of many KM-sized objects and a number of dwarf planets. there might be 70,000 Kuiper belt objects. the Kuiper belt is the repository of long period comets, those with periods > 200 years.
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what is an extra-solar planet
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planets orbiting other stars
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what are the 3 principal ways of discovering extra-solar planets
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periodic variations n the radial velocity of a star
transits of a large planet in front of a star- you measure a decrease in the light of the star
direct imaging
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how many extra-solar planets have we discovered so far
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694
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photosphere
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suns atmosphere
pale yellow layer of the sun that we see every day. T ~ 5800 °K
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chromosphere
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suns atmosphere
above photosphere. see colored loops of gas there during a total
solar eclipse. ~4500 < x < 10000 °K
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corona
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suns atmosphere
hottest region. lowest density. observe during total solar eclipse
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the nature of neutrinos that come from the sun
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hydrogen fusion emits neutrinos
-neutrino: light atomic particle with no charge
-very weak interactions with matter
-should escape the core freely
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how do we know that sunspots are cooler than the rest of the photosphere
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it is a contrast effect. the temp is lower and a cooler black body gives off less light
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magnetic fields in the sun
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-produce sunspots
-polarity of sun spots reverses every 11 years
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cause of the aurora borealis/australis in the Earth’s atmosphere
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when sun sis experiencing a solar maximum. lots of spots, strong magnetic storms, strong solar wind. when wind hits Earth’s atmosphere, radio transmission is disrupted. observed as northern lights.
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relationship between parallax of stars and the distances
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d(pc) = 1/ac
-greater the parallax, smaller the distance
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what is a parsec
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“parallax of one second of arc”. 3.26 light years.
reciprocal of parallax in arcsec
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what are stellar radial velocities?
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measured from the Doppler shift of the lines in a stars spectrum
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what are proper motions
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number of arc seconds/year that a star moves with respect to the
distance background of stars or galaxies
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inverse square law of light intensity
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allows us to calculate the stars luminosity if we know its distance or calculate distance if we know its luminosity
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what do we mean by the absolute magnitude of a star
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apparent magnitude a star would have it d=10pc
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what does this mean? Mv = mv + 5 – 5 log d? (the apparent magnitudes have to be corrected for any effects of interstellar dimming due to dust. otherwise your distances aren’t right)
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Mv: absolute apparent magnitude
mv: apparent visual magnitude correct for any dimming by interstellar dust
d: distance in parsec
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Hertzsprung-Russell Diagram: what is a plot of
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plot of intrinsic luminosities vs. photospheric temperatures.
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Hertzsprung-Russell Diagram: what is the range of photospheric temperatures
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range of photospheric temperatures: 3000-30000 °K
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Hertzsprung-Russell Diagram: what is the range of luminosities
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range of intrinsic luminosities: 10-4-106
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Hertzsprung-Russell Diagram: what is the range of masses of main sequence stars
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range of mass of main sequence stars: 0.08 to 60-100 solar masses
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what does this mean: TMS is proportional to M-2.5
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the lifetime of a main sequence star
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how can we get observational confirmation from star clusters concerning the main sequence lifetimes of stars?
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-all stars in a cluster lie at about the same distance from earth
-all stars in the cluster were formed at about the same time (w/in a few mil. years)
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spectroscopic binaries
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revealed by the Doppler stars of the 2 stars in a close binary system
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eclipsing binaries
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revealed by mutual eclipses of 2 stars. the observer must be close to the
plane of the orbit of the 2 stars
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how does interstellar dust affect the light of stars along the line of sight
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dimming, reddening, star counts
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what fraction (by mass) of the interstellar medium is in gas and what fraction is dust
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~1% is dust
99% is gas
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how long is the collapse from interstellar dust
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5 million years
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how long is the protostar
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30 million years
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how long is the main sequence phase
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10 billion years
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how long is the giant phase
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about 1 billion years
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how long is the planetary nebula
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50000 years
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how long is the white dwarf star
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forever
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What is the CNO cycle? it is the principal energy generation mechanism for which kind of stars
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faster chain of hydrogen fusion because reactions also occur with carbon, nitrogen,
and oxygen
1.1+ solar mass stars (high mass stars)
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what is the minimum temperature to run the proton-proton cycle in a stars core
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10 million K
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why are Cepheid’s importanT
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imbalance between pressure of stars layers and energy transport. causes
star to pulsate (periods of days)
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why are RR lyrae stars important
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found in globular clusters. about 30 times brighter than the sun (periods
of hours)
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what is the period-luminosity relation?
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relation between the pulsation period and absolute
brightness
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relation between the pulsation period and absolute
brightness
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runs out of fuel -> collapses -> turns into a supernova -> neutron star/black hole
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what is degenerate electron matter
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as the Hydrogen is converted to Helium in the core, the gas becomes denser as the energy levels are filled
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what is the maximum mass of a white dwarf star
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1.4 solar masses (Chandrasekhar’s limit)
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what does fully convective mean
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the gas in the outer layers of stars mixes down into the core
completely
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stars less than 0.4 solar masses are fully convective. how long do they last as main sequence stars?
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10 billion years
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how long do they last as main sequence stars? do they become giant stars?
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NO
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how is a stars evolution changed if it has a really close companion
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higher mass star evolves first. expands until it loses material due to other stars gravitational pull. material flows to smaller star & becomes a white dwarf. when second star is giant enough to dump a material to the white dwarf, H collects on white dwarf and star gets temporarily bright…
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what is the structure of a 10 solar mass star prior to its explosion as a type 1 supernova
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iron tightly bound nucleus. nuclear reactions cause outer layers to squeeze down causing it to explode as type 2 supernovae
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what do we mean by the term standard candle? what good are they?
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an object whose brightness at some time (or mean brightness) is known an can be used to determine astronomical distances
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what are type 1a supernovae better standard candles for galaxies more than 25 megaparsecs distant (compared to say, Cepheid’s)
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ype 1a supernovae are 4 billion times brighter than Cepheids. thus hey can see much farther than Cepheids
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what are the mean densities of the sun, a typical white dwarf star, a neutron star
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sun: 1.4g/cm3
white dwarf: several tons/teaspoon
neutron star: 1015 g/cm3
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how massive is the black hole in the center of our galaxy
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2.6 0.2 million times the mass of the sun
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Study Guide ASTR 101