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| contains... millions of billions of stars, gas, dust, and black holes |
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| three major types of galaxies |
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Definition
1. elliptical 2. spiral 3. irregular |
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a galaxy that is round or elliptical in outline and contains - little gas and dust
- no disk or spiral arms
- few hot, bright stars
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a galaxy with an obvious disk component containing.. - gas
- dust
- hot, bright stars
- spiral arms
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a galaxy with a chaotic appearance large clouds of gas and dust both pop I and pop II stars with spiral arms |
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a spiral galaxy with an elongated nucleus resembling a bar from which spiral arms originate 2/3 of galaxies (including ours) classified in three groups: SBa, SBb, SBc |
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| Large and small magellanic cloud |
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Definition
an irregular galaxy visible in the southern sky that is a satellite of our Milky Way galaxy |
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| two standard candle methods |
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Definition
1. Cephid method (period-luminosity relation) 2. Type 1a supernovae (collapse of an accreting white dwarf in a binary system) |
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| object of known brightness that astronomers use to find distance |
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| the calibration used to build a distance scale reaching from the size of Earth to the most distant visible galaxies |
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| type 1a supernovae are better to use in measuring very long distances than Cepheid variable stars because.... |
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Definition
| ... type 1a supernovae are more luminous |
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| compared with spiral galaxies, elliptical galaxies lack (2 things)... |
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Definition
... lack hot, bright stars ... lack visible gas and dust |
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the amount by which you look into the past when you look at a distant galaxy a time equal to the distance to the galaxy in lightyears |
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Definition
galaxies in distant superclusters are moving away with recession velocity proportional to their distance |
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| The Hubble Law proves that... |
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Definition
proves that the universe is expanding by estimating distances to galaxies |
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Definition
a measure of the rate of expansion of the universe the avg value of velocity of recession divided by distance = 70 km/Mpc |
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| How did Edwin Hubble prove that there are other galaxies far outside the Milky Way? |
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| Hubble's measurement of the distance to the Cepheid varibles in the Andromeda Galaxy demonstrated that it was not a nearby nebula but an island of stars very far away. |
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a method of determining a galaxy's mass by observing the orbital velocity |
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| how are galaxies distributed in the universe? |
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Definition
| _ are not distributed in isolation, but in clusters and superclusters |
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a cluster containing over 1000 galaxies mostly elliptical scattered over a volume of about 3 Mpc in diameter |
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an irregularly shaped cluster that contains less than 1000 galaxies many are spiral no giant ellipticals not condensed toward center |
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| the small cluster of a few dozen galaxies that contain our Milky Way |
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| What happens when two galaxies collide or merge? |
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Definition
their clouds of gas and dust colide, creating shock waves which trigger a tremendous amount of star formation stars are so far apart that they rarely collide |
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| two effects of colliding galaxies |
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a galaxy undergoing a rapid burst of star formation very rich in gas and dust bright in infrared |
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| a long streamer of stars, gas, and dust torn from a galaxy during its close interaction with another passing galaxy |
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a galaxy that resembles a ring around a bright nucleus result of a head-on collision of two galaxies |
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| the theory that large galaxies absorb smaller galaxies |
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a galaxy whose center emits large amounts of excess energy- often in the form of radio emission suspected to have massive black holes in centers in which matter flows |
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| how big are active galaxies |
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Definition
approx the size of our solar system |
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| three types of active galaxies |
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Definition
1. peculiar galaxies 2. seyfert galaxies 3. BL Lacertae objects/blazars |
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| peculiar galaxies appear to.. |
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Definition
| appear to be blowing themselves apart |
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Definition
an otherwise normal spiral galaxy with an unusually bright small core that fluctuates in brightness believed to indicate that the core is erupting strong emission lines |
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BL Lacertae objects aka blazars |
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Definition
type of active galaxy have featureless spectra with brightness that can vary by a factor of 15 in a few months |
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Blazar aka Bl Lac objects |
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Definition
objects that resember quasars, thought to be highly luminous cores of distant active galaxies |
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| double lobed radio source |
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Definition
| a galaxy that emits radio energy from two regions (lobes) located on opposite sides of the galaxy |
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Definition
small, powerful source of energy believed to be the active core of a very distant galaxy these galaxies are very bright (100Xlum) with supermassive BH traveling away from us at far speeds spectra highly redshifted probably normal stars |
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Definition
| an attempt to explain the different types of active galactic nuclei using a single model viewed from different directions |
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evidence for supermassive black hole to be cause for energy source.. |
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Definition
| ...huge rotation near the centers of active galaxies and high-velocity jets ejected along their axes of rotation |
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| our milky way might have erupted as a... |
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Definition
| quasar in the past when gas and dust were more plentiful |
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