Term
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Definition
| The tilts of the Earth’s axis |
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Term
| Will a planet in retrograde motion rise in the east or west? |
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Definition
| Rise in the east and set in the west |
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Term
| Problem computing circumference from angle of shadow |
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Definition
| (angle(°) )/(360°)= distance/circumference |
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Term
| What are right ascension and declination? |
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Definition
| RA = longitude, DEC = latitude |
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Term
| Two phenomena which prove that the Earth moves |
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Definition
| Stellar parallax and the aberration of starlight |
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Term
| Conversion of RA and DEC to decimal degrees |
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Definition
| 1 hr = 15°, 1 min = .25°, 1 sec = .004167°, 1’ = (1/60) °, 1” = (1/3600) ° |
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Term
| Escape velocities of Mars, Earth, and Saturn |
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Definition
| From smallest to largest: Mars ? Earth ? Saturn |
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Term
| How did Newton deduce that the force of gravity obeyed an inverse square law? |
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Definition
| He tried various power laws to see which yielded Kepler’s third law |
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Term
| Possible consequences of precession of Earth’s axis |
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Definition
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Term
| Why is the inner core of Earth solid? |
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Definition
| Higher temperature and especially higher pressure at the center (crystallized iron and some nickel) |
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Term
| Directions of vibration and propagations in S waves and P waves |
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Definition
| S-waves: vibration is perpendicular to the direction of propagation, P-waves: vibration is parallel |
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Term
| Problem on distance, velocity, and time with seismic waves |
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Definition
| t = d/v d = distance, v = velocity, t = time |
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Term
| Greenhouse gases are equivalent to what in a greenhouse? |
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Definition
| The glass in the greenhouse |
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Term
| Evidence that the Earth has a liquid core |
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Definition
| S-waves don’t get through to the other side |
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Term
| Composition of the plates on Earth’s surface |
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Definition
| A combination of crust and mantle |
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Term
| If you were on a beach and the water went out… |
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Definition
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Term
| Difference between lunar rilles and rays |
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Definition
| Rilles = canyons, rays = streaks that radiate out from craters |
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Term
| Time dependence (if any) of eccentricity of the Moon’s orbit |
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Definition
| Varies periodically with a period of about 206 days |
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Term
| Definition of an eclipse season |
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Definition
| A period of time in which eclipses are possible) a few days, 2 eclipse seasons per year |
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Term
| Problem with the twin formation theory of the formation of the Moon |
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Definition
| It does not explain the density difference |
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Term
| Conditions for the highest spring tides |
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Definition
| New/full moon, moon closer to Earth’s orbit (at perigee) |
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Term
| Problem (if any) with the giant impact model of the formation of the Moon |
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Definition
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Term
| Relation between Moon’s orbital and synodic periods |
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Definition
| Synodic = phase period, 29 days, sidereal = true revolution, 27 days, 2 days shorter |
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Term
| Problem on ratio of apogee to perigee distances |
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Definition
| rA/rp = ((1+e))/((1-e)) e = eccentricity, rA = a(1+e), rp = a(1-e) |
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Term
| Characteristics of extrasolar planets detected thus far |
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Definition
| Masses of .5 to 5 times that of Jupiter, distances less than 1 AU, Eccentric orbits |
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Term
| Reason why there are two main types of planets |
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Definition
| 4 inner planets: rocky, iron cores, smaller, thin atmospheres (terrestrial, like Earth) and 4 outer planets: gaseous/liquid, larger, rich atmospheres (Jovian, like Jupiter) |
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Term
| Bias of the Doppler method |
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Definition
| Biased toward detecting massive planets that orbit at small distances close to their parent stars (only big and nearby planets detected) |
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Term
| Advantage of the transit method |
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Definition
| It can determine a planet’s diameter, and thus, can also calculate its density |
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Term
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Definition
| an empirical numerical rule which correctly predicts the relative distance of most of the planets. Start with 0, 3, then double each preceding number (6, 12, etc.), add 4 to each number, and divide the result by 10. |
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Term
| Why is there no planet in the asteroid zone? |
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Definition
| Jupiter’s gravity disrupted the accretion process |
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Term
| Problem to determine semimajor axis from period |
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Definition
| (exoplanet orbits a star of 1 solar mass) p2= a3 (AU) p = period, a = semi-major axis, put period in terms of years |
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Term
| Surface features of Mercury compared with those of the Moon |
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Definition
| Scarps and volcanoes are not on the Moon (no iron core in the Moon) |
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Term
| Time taken for a radar signal to go to Venus and back |
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Definition
| Distance (to planet) = speed of light * timeSpeed of light = c = 3.00*108 m/s (or 2.99*108 m/s) |
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Term
| Main type of surface features on Venus |
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Definition
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Term
| Name of the current mission to Mercury |
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Definition
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Term
| What were the canals on Mars as seen by Percival Lowell? |
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Definition
| They were an optical illusion |
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Term
| Uses of radar for studying Venus |
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Definition
| Distance, rotation period, surface features—on Titan, also surface elevation |
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Term
| Surface features on Mars and presence of liquid water |
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Definition
| Dry river beds and lake beds ? climate change |
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Term
| Interior structure of Jupiter and Saturn |
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Definition
| Rocky core ? liquid metallic hydrogen (H) ? molecular hydrogen (H2) |
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Term
| How does the Cassini mission penetrate the haze of Titan? |
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Definition
| Radar (bright surface = rough, dark surface = smooth) |
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Term
| Location of the ring systems of the giant planets |
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Definition
| Planet ? rings ? satellites |
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Term
| Why is the space near Jupiter a dangerous environment? |
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Definition
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Term
| Reason why Uranus and Neptune are blue |
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Definition
| Methane absorbs red light |
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Term
| Probable explanation for the odd tilt of Uranus’s axis and its satellite orbits |
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Definition
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Term
| Calculation of the Roche limit |
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Definition
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Term
| Temperature at a distance of one of the Jovian planets |
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Definition
| Inverse square law: T2/T1 = v(d1/d2) |
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Term
| Name of a piece of rock from space which lands on Earth |
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Definition
| Meteoroid (in space), meteor (in sky), meteorite (on Earth) |
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Term
| Dependence of kinetic energy of an asteroid on diameter and speed |
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Definition
| KE = 1/2 mv2, m = d3 ? KE = d3v2 |
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Term
| How do we know what asteroids are made of? |
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Definition
| Reflection spectrum, minerals reflect wavelengths |
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Term
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Definition
| Earth goes through the comet’s orbit while going around the Sun |
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Term
| Nighttime sky from an asteroid |
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Definition
| You would not see your neighbor (aka spacing is very wide) |
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Term
| Cause of the two tails on some comets |
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Definition
| Dust tail is caused by radiation pressure (photons), ion tail is driven by solar wind (particles from the Sun) |
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Term
| Effect of emission and absorption on an electron in an atom |
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Definition
| Absorption: increases energy level, emission: reduces energy level |
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Term
| Wien’s law problem on a logarithmic scale |
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Definition
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Term
| Why are neutrinos a good probe of stellar interiors? |
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Definition
| They are generated by nuclear reactions of the Sun, they interact weakly with matter so we can observe |
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Term
| Why doesn’t the Sun collapse? |
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Definition
| Balance between pressure (pushing outward) and gravity (pushing inward), known as hydrostatic equilibrium |
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Term
| Name of the series of reactions which produce the Sun’s energy |
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Definition
| Proton-proton chain (deuteron ? helium 3 ? helium 4), also P-P chain |
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Term
| What is the Mauder minimum? |
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Definition
| A period of low sun spot activity (ex: during 1620-1710) |
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Term
| Why do sunspots appear dark? |
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Definition
| They are regions of concentrated magnetism, deflect electrons and inhibit convection (light energy), reduce energy flow |
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Term
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Definition
| A gravitationally-bound star, two binary stars orbit each other |
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Term
| Determination of individual masses from combined mass and mass ratio |
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Definition
| M1 + M2 = a3/p2 , M1 + M2 = c (constant) |
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Term
| Parallax of the nearest star as seen from Neptune |
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Definition
| PNeptune = 30 PEarth (30 AU : 1 AU) |
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Term
| What is the mass-luminosity relation? |
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Definition
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Term
| Why are stellar parallaxes difficult to measure from the ground? |
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Definition
| The atmosphere blurs the images |
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Term
| Most common stars in the Sun’s neighborhood |
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Definition
| Red dwarfs (class M/M5/MV on the main sequence) |
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Term
| Original classification of stellar spectra by Annie Cannon |
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Definition
| Simple spectra ? most complex spectra |
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Term
| Problem to determine main sequence lifetime from mass and luminosity |
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Definition
| t = M/L * 1010 year (M and L are in solar units) |
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Term
| Range of masses of stars which will eventually become white dwarfs |
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Definition
| Minimum of .4 solar masses, maximum of 8 solar masses |
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Term
| Fate of a single white dwarf |
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Definition
| Cools down after formation |
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Term
| What property of a star changes most during the main sequence stage? |
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Definition
| Composition in the core (He increases) |
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Term
| Meaning of hydrostatic equilibrium |
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Definition
| Balance between forces of gravity and pressure |
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Term
| Use of the main sequence turn-off point for a cluster |
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Definition
| Used to determine the age of a cluster |
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Term
| Types of pulsating stars that are useful as distance indicators |
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Definition
| RR Lyrae, Cepheids, Miras |
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Term
| When are elements heavier than iron produced? |
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Definition
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Term
| Comparison of escape velocities of a white dwarf and a neutron star |
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Definition
| Vesc = v(2GM/R), neutron star has greater escape velocity |
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Term
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Definition
| A rotating neutron star that produces a “lighthouse effect” temperature of gas in a supernova remnant |
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Term
| Doppler shifts in supernova spectra |
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Definition
| Red shift due to expansion of universe, also blue shift due to mass approaching us at a great velocity (we don’t see the red shift) |
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Term
| Basic observational difference between Type I and Type II supernovae |
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Definition
| Type I: no hydrogen lines vs. Type II: hydrogen lines |
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Term
| Basic physical difference between Type Ia and Type II supernovae |
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Definition
| Type Ia: from a white dwarf vs. Type II: from a massive star (O or early B) |
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Term
| What best reveals the spiral structure of the Milky Way? |
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Definition
| Studies and observations of our own galaxy, combined with general features known to occur in other galaxies, have led us to infer that the Milky Way is a flat disk with spiral arms. Shapley’s studies proved it was a flat disk, and other galaxies of that shape have extending spiral arms. |
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Term
| Differences between low-metallicity and high-metallicity groups of globular clusters |
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Definition
| Low metallicity: metallicity of less than -0.8, about 75% of the Milky Way’s globular clusters, generally older, spatial distribution more spherical, reflect early universe conditions, more RR Lyrae clusters. High metallicity: metallicity greater than -0.8, about 25% of the Milky Way’s globular clusters, generally younger, spatial distribution is more flattened, reflect the shape of galactic flattening over time, less RR Lyrae clusters |
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Term
| Main parts of the Milky Way and the Sun’s position in it |
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Definition
| A disk, a surrounding halo, a flattened and somewhat elongated bulge of stars at its center, spiral arms that extend outward, a core/galaxy nucleus, the Sun is about 2/3 of the way out in the disk, NOT at the center |
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Term
| Why is our line of sight to the globular clusters clear? |
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Definition
| Many contain RR Lyrae stars, which are pulsating stars, globular clusters can be seen from great distances. Unlike open clusters, in which the stars eventually escape and the cluster dissolves, globular clusters pull the stars into a denser ball, there is not as much dust obscuring the view, and the larger number of stars in these clusters creates a stronger gravity, which pulls them in closer. Globular clusters outline the halo and bulge. |
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Term
| Why star counting cannot be used to locate the galactic center |
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Definition
| Interstellar dust; it dims and blocks our view of distant parts of the galaxy, thus it affects our ability to measure distances to stars and to determine the size of the Milky Way. The dust dims the brightness and alters the colors of stars we see through it, may even dim it to the point of invisibility. Also, each star is pulled in by gravitational force towards the center of the galaxy, and follows its own orbit. |
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Term
| What maintains the spiral structure of the Milky Way? |
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Definition
| Density-wave theory: waves of stars and gas sweep around the galactic disk, we see it as a spiral arm, very wave-like. Some stars have greater gravitational force, which pulls in other stars temporarily and creates a “clump,” where stars can collide and form new stars. SSF Theory: self-propogating star formation, at a random point in the disk of a galaxy, a gas cloud collapses and turns into stars. The stars heat the gas around them, explode as supernovas, generate disturbances that make the surrounding gas clouds collapse and turn into stars. This keeps triggering more gas clouds to collapse and form additional stars, so star formation spreads across the galaxy’s disk, forms a spiral due to the difference in rotation rate between the inner and outer parts of the disk. |
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Term
| Problem to determine the mass of the central object by Kepler’s Third Law |
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Definition
| m + M = a3/p2 , m = mass , of smaller object , M = mass of larger object (sometimes not used), a = distance between objects (also semi-major axis), p = years to complete one orbit |
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Term
| The three main types of galaxies |
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Definition
| Spiral (barred and S0), elliptical, and irregular |
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Term
| Problem to determine distance from recession velocity |
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Definition
| v = Hd v = velocity, d = distance, H = Hubble constant = 70 (or 71) km/megaparsecs, answer given in megaparsecs |
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Term
| What is the power source for active galaxies? |
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Definition
| Accretion disks around immense black holes, galaxy centers = black holes of at least 1 million solar masses |
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Term
| Evidence for supermassive black holes at the centers of galaxies |
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Definition
| Images from the Hubble Space telescope; disk shown, gas falling into disk releases gravitational energy, heats material to millions of Kelvins, some material boils off into space, stars and gas are orbiting the core at high speeds, must be bound in by a black hole, emits no light/radiation, both massive and dark, accounts for the difference in observed mass vs. calculated mass |
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Term
| Evidence that active regions of quasars are small |
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Definition
| Their light variability; if a quasar varies in brightness in a time as short as a few days, then the emitting region can be no more than a few light-days across in diameter (aka, very small diameter compared to the rest of the universe), proof from the delay of light from the nearest side of quasar vs. delay of light from the farthest side of quasar |
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Term
| Evidence for dark matter in clusters of galaxies |
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Definition
| Evidence comes from observations of the motion of galaxies within clusters; galaxies in clusters orbit too rapidly for their luminous mass. Also, evidence comes from the hot gas they contain—this infers a strong inward gravitational pull on the gas to keep it contained |
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Term
| Explanation of pairs of quasars with identical spectra |
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Definition
| The quasar “companions” are actually images of a single quasar created by a gravitational lense |
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Term
| Celestial objects which can be directly imaged |
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Definition
| Objects whose redshift (z) is less than 1.645 |
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Term
| Celestial objects which cannot be directly images |
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Definition
| Objects whose redshift (z) is greater than 1.645 |
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Term
| Temperature of matter which emitted the cosmic background radiation, and reason it appears to have a temperature of 2.73 K today |
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Definition
| Temperature = approx. 3000 K. Initially, it had much shorter wavelengths, but those wavelengths have been stretched out over billions of years by the stretching of space associated with the expansion of the universe. 2.73 K is due to a redshift effect because of the expansion of the universe, rather than a cooling effect. |
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Term
| How we know that the expansion rate of the universe is accelerating |
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Definition
| The rate of expansion has been increasing. Dark energy is used to account for this expansion rate. Normal/dark matter would act to slow the expansion rate. With the universe’s thinning density over time, it means that the accelerating effect of the repulsive dark energy component dominates the decelerating effect of the attractive gravitational force. |
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Term
| The four distances used in cosmology |
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Definition
| Luminosity distance, Now distance, Light-travel-time distance, and Angular-size distance |
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Term
| Objects which can be used to test the angular-size vs. red shift relation at high redshift |
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Definition
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