Details Title: Astronomy Final Description: ast301 final Total Flash Cards: 80 Created: 12/02/2008 20:24:18		New Users: To study from this flashcard set, or to create your own your own study flash cards, REGISTER HERE. Existing Users: CLICK HERE. Additional Astronomy Flashcards
Cards in this set: Term Why does hydrogen burning keep the Sun in gravitational equilibrium? Definition as gravity pushes inward, energy released from fusion maintains the internal gas pressure that pushes outward Term Why does it take so long for a photon in the Sun's center to get to us? Definition the photon's "random walk"-- plasma in solar interior so dense that photon can't travel far before it interacts with an electron, deflected in another direction Term in a visual binary... Definition we can see both stars directly Term in an eclipsing binary... Definition we see a change in brightness (change of light curve of star when one eclipses the other) Term in a spectroscopic binary... Definition we see a change in radial velocity (doppler shift in star's spectral lines) Term if 2 stars have the same temperature and different luminosity, is mass the same? Definition no Term if 2 stars have different temperatures and the same luminosity, can the mass be the same? Definition yes Term as luminosity increases... Definition ...mass increases Term H-R diagram of globular cluster is useful because Definition it determines the age of cluster at "main-sequence turnoff" point, where hot, short-lived stars have died Term Why does a collapsing gas cloud form a disk? Definition gas contracts under force of gravity---Conservation of Angular Momentum---gas flattens into spinning disk Term stars with mass <.08 solar mass don't fuse H because.. Definition they can't compress & there is no nuclear burning because degeneracy pressure overcomes gravity Term when star burns all H in core, it expands because Definition core H exhausted---core shrinks/hears---H shell burning occurs---star expands into a red giant Term solar mass stars do not enrich the ISM because... Definition they have no helium capture or supernovae explosions Term what are the 3 types of "stellar corpses"? Definition white dwarf (least massive) neutron star black hole (most massive) Term what supports a white dwarf? Definition electron degeneracy pressure Term what supports a neutron star? Definition neutron degeneracy pressure Term what supports a black hole? Definition nothing; it has collapsed in on itself Term what mechanism creates a pulsar? Definition (1)iron core collapses into neutron star (2)neutron star spins rapidly (3)has magnetic field misaligned with its spin axis (4)particles trapped in magnetic field, collide with other particles (5)collisions give off light Term what causes superbubbles and galactic fountains? Definition supernovae explosions Term superbubble Definition expanding shell of hot gas given off by supernovae explosion Term Why does the rotation curve of our Solar System not require dark matter but that of the Milky Way does? Definition not enough dark matter enclosed in the solar system to affect it Term why are cepheids used as standard candles? Definition we can det each cepheid's luminosity by its period Term why might we be able to use gamma-ray bursts as standard candles? Definition //QUASAR, except all material accretes at once Term quasar Definition brightest type of active galactic nucleus Term active galactic nuclei Definition unusually luminous centers of galaxies powered by accretion onto supermassive black holes Term how did Hubble discover his law? Definition by measuring the redshifts of galaxies & estimating distances, using the brightest obj. in every galaxy as a standard candle Term the Universe is expanding but our bodies are not because... Definition Hubble's Law applies to big distances, its affect on us negligible Term distance ladder fm closest to farthest: Definition radar > parallax > main sequence fitting > cepheids > white dwarf supernovae > Hubble's Law Term how to det dist to nearby stars? Definition parallax Term how to det dist to obj in milky way? Definition main sequence fitting Term how to det dist to nearby/distant galaxies? Definition white dwarf supernovae (by way of distant standards) Term in theory, halo stars are older than disk stars because... Definition halo stars formed before galaxy's gas fell into disk; disk stars formed after collapse Term by observation, we know halo stars are older than disk stars because Definition new stars only formed in disk (very little (cold) gas in halo) and the halo lacks heavy elements Term nature argument in elliptical galaxies Definition (1)low spin (2) high star formation efficiency Term nurture argument in elliptical galaxies Definition (1)collisions/mergers (2)accretions/cannibalism Term arguments for "quasars are powered by accretion onto a supermassive black hole" Definition because black hole explains quasar's extreme luminosity, its small size, and how massive it is Term more quasars in the past because Definition black holes have used up fuel, leaving only black hole (because galaxies have already been created) Term stars w/ high concentrations of elements other that H and He likely formed in.. Definition elliptical galaxies Term the first estimate of where the center of the Milky Way is came from... Definition locations of globular clusters Term what causes a pulsar? Definition misalignment of the rotation axis and magnetic field axis Term galactic fountain is due to Definition gravitational pull of the disk Term compared to a blue galaxy, a red galaxy has.. Definition older stars Term Where are blue stars? Definition on the leading side of a spiral arm Term how are heavy elements supplied to the ISM? Definition -helium capture -supernova Term If the temp of the Sun's core were to increase due to an increase in the rate of fusion.. Definition the core would expand, reducing the pressure and temperature, and the rate of fusion would decrease back to its original level Term physical mechanism responsible for the solar wind? Definition magnetic fields get generated in the convective zones. As they make their way to the surface, the fields get released into the corona and eventually break, causing material to shoot away from the Sun. Term after sun converts H to He, the remaining H... Definition converts to other forms of energy and ultimately emitted in the form of radiation Term Annie Cannon and Cecilia Payne-Gasposchkin known for Definition understanding stellar spectral classification Term what is a red giant? Definition when He burning in core Term Why is measurement of neutrinos important? Definition means that we understand energy mechanism in the Sun Term Why is measurement of neutrinos important? Definition means that we understand energy mechanism in the Sun Term All atoms prominant in biological systems are created... Definition in high-mass stars Term globular clusters are important to study because Definition all stars are about the same age Term a star spends about 10% of its life on Definition the giant branch Term the Sun is mainly composed of Definition H Term the Proton-Proton chain creates.. Definition neutrinos, gamma-rays, and positrons Term a main sequence star converts Definition H --> He Term the idea that an explosion that we see on the Sun actually occurred 8.3 minutes ago is known as Definition lookback time Term we can detect MACHOs by Definition gravitational lensing events Term a standard candle is Definition a light source of known brightness Term a flat universe means that Definition our universe is at the critical density Term galaxies with extremely bright centers are called Definition active galactic nuclei Term 3 facts about bullet cluster Definition (1)gas @ diff location than galaxies (2)dark matter at diff location than gas (3)proves dark matter exists Term Hubble's law implies that Definition the Universe's age is finite Term Galactic bulges and halos are called Definition spheroids Term cepheids are important since they measure distances to Definition nearby galaxies Term WIMPs are hard to detect because Definition they do not have much of an effect on other particles Term 3 facts about quasars Definition (1)inside galaxies (2)more common in the past (3)supermassive black holes actively eating Term why is the H-R diagram for globular clusters important? Definition the location of the main-sequence turnoff point determines the age of the globular cluster Term solar mass stars do not enrich the ISM because Definition -no He capture -no supernovae Term how pulsar created Definition high-mass star goes supernova---neutron star---degeneracy pressure and a lot of spin---misaligned axes Term how does a pulsar give off light? Definition (1)mag field not align with spin axis (2)particles trapped in mag field collide with other particles Term how did Hubble discover Hubble's Law? Definition measured period of cepheids in Andromeda Term distance ladder Definition radar---parallax---cepheids---white dwarf supernova Term arguments for why quasars pwrd by accretion onto supermassive black hole: Definition quasars= extremely small and massive (mass det by ext. brightness) Term 3 ways to measure mass of galaxy clusters Definition (1)measure radial velocity of galaxies (2)gravitational lensing (3)x-ray to see hot gas--observe temp/luminosity = mass Term There were more quasars in the past because Definition matter that used to create friction(ENERGY SOURCE) have fallen into the black hole, rendering it invisible Term observational evidence for "dark matter outweighs normal matter by 9 to 1" Definition (1)rotation curve of our galaxy (2)bullet clusters Term why did Einstein create the cosmological constant? Definition to represent a repulsive force/energy that might cause universe to accelerate with time; counter gravity keep galaxies from falling in on each other Term active galactic nuclei is.. Definition unusually luminous centers of some galaxies powered by accretion onto supermassive black holes (quasars=brightest type)