Term
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Definition
| A collapsed old star with such dense mass that even EM radiation cannot escape. |
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Definition
| Singularity: a mathematical point of infinite density with zero radius inside a black hole. |
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Term
| The first suggestion that there were collections of stars beyond our Milky Way in the universe was made by.. |
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Definition
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| What separates a black hole from the rest of the universe? |
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Definition
| Its event horizon.. The event horizon is the point, once crossed, from which nothing can escape the inward gravitational pull of the old collapsed star. |
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Term
| The distance from a black hole singularity to the point where nothing can escape a black hole (its event horizon) is called what? |
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Definition
| Its Schwarzschild radius. The distance from a black hole singularity to the point where nothing can escape a black hole (its event horizon) is the Schwarzschild radius. |
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Term
| A nonrotating black hole is called what? |
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Definition
| A Schwarzschild black hole. |
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Term
| Where is the event horizon of a black hole located? |
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Definition
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Term
| What important role do Cepheid variables have in astronomy? |
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Definition
| Distance measurements to distant galaxies. |
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Term
| A rotating black hole is called what? |
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Definition
| A Kerr or Hawking black hole |
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Term
| What is a successful technique for finding candidates for black holes in our galaxy? |
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Definition
| Detection of x-rays from a binary star undergoing mass exchange, where mass of component star can be determined. |
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Term
| Beside rotating and nonrotating black holes, how many other types are known to exist? |
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Definition
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Term
| If nothing can escape from a black hole, how can we detect black hole candidates by the x-rays they emit? |
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Definition
| The x-rays come from the highly compressed accretion disk just outside the event horizon. |
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Term
| What can you never know about a black hole? |
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Definition
| What type of material is inside it. |
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Term
| An orbiting disk of matter spiraling in towards a black hole is called what? |
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Definition
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Term
| In terms of black holes, what is a wormhole? |
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Definition
| A hypothetical direct connection from one black hole to another part of spacetime. A complete fantasy, no such objects exist. |
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Term
| The Andromeda Galaxy (M31) can be described as.. |
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Definition
| a spiral collection of stars, dust, and gas, 2 million ly away. |
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Term
| A virtual particle is what? |
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Definition
| A particle and its antiparticle are created simultaneously in pairs and then are annihilated so quickly that we cannot even know that they ever existed. |
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Term
| What is it that makes the study of the structure of our own Galaxy more difficult than that of much more distant spiral galaxies? |
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Definition
| Most of our galaxy is hidden behind dense gas and dust clouds in the galactic plane. |
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Term
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Definition
| is one of many billion of galaxies in the universe. |
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Term
| The dimensions of the disk of our Milky Way Galaxy are.. |
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Definition
| diameter 100,000 ly; thickness 2000 ly. |
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Term
| The Milky Way in which the Sun resides is an example of which type of galaxy? |
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Definition
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Term
| Where is the solar system located in our Galaxy? |
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Definition
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Term
| Approximately how far is the Sun from the center of our galaxy? |
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Definition
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Term
| What is the significane of the object Sagittarius A* ("Sagittarius A-star") in our Galaxy? |
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Definition
| It appears to be the actual nucleus of the Galaxy. |
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Term
| Much of the mass of our Galaxy appears to be in the form of "dark" matter of unknown composition. At present, this matter can be detected only because.. |
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Definition
| its gravitational pull affects orbital motions in the Galaxy. |
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Term
| Who developed the classification system that divides galaxies into spiral, elliptical, and irregular and classifies spirals by the size of their nuclear region and the tightness of winding of their arms? |
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Definition
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Term
| The Andromeda Galaxy (M31) is best described as |
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Definition
| `a spiral collection of stars, dust and gas, 200,000 ly across |
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Term
| How are galaxies spread throughout the universe? |
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Definition
| Clusters of galaxies exist that are themselves often clustered into superclusters. Clusters and superclusters appear to be distributed on surfaces surrounding empty regions of space. |
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Term
| In discussing galaxies & the universe, astronomers often talk about "voids." What are voids? |
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Definition
| Volumes of space hundreds of millions of light-years across that contain almost no galaxies |
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Term
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Definition
| A cluster of about 40 galaxies of which the Milky Way is a member of |
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Term
| Which single major problem perhaps puzzles astronomers the most as they attempt to interpret the properties and behavior of clusters of galaxies? |
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Definition
| The missing-mass problem, where the amount of mass needed for galactic cluster stability is estimated to be at least 10 times more than the observed visible mass |
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Term
| Who first showed that the recessional speeds of galaxies increase with increasing distance from the Earth? |
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Definition
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Term
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Definition
| Distant galaxies are all moving away from us, with speed increasing with increasing distance. |
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Term
| The primary evidence for the expanding universe concept is |
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Definition
| the redshift of light from distant galaxies, which increases with distance of the galaxy from the Earth. |
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Term
| The mathematical form of the Hubble law for the expanding universe concept relates the velocity of recession v to the distance of the observed object d ( with H0 the Hubble Constant) as follows: |
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Definition
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Term
| The energy output of a typical quasar per second is equal to that emitted by the Sun in.. |
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Definition
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Term
| What is the most outstanding feature of a quasar compared to other objects in deep space? |
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Definition
| Its prodigious output of energy. |
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Term
| Quasars in our universe are |
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Definition
| relatively common, with over 200,00 identified so far. |
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Term
| Quasars all appear to be.. |
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Definition
| moving away from us at very high speeds, up to about 90% of the speed of light. |
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Term
| The distance to the bright quasar 3C 273 is estimated to be.. |
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Definition
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Term
| In 2004 a blazar of 10 billion solar masses was discovered at a distance of 12.5 billion ly. What was particularly intriguing about this discovery? |
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Definition
| This blazar must have been formed very early in the history of the universe-- too early, presumably, to have that much mass concentrated together. |
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Term
| Which scientist discovered that the equations he had derived predicted an expanding universe, then modified his equations to eliminate this expansion? |
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Definition
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Term
| In the expansion of the universe, the expansion takes place.. |
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Definition
| primarily in the huge spaces between clusters of galaxies; "small" objects like galaxies or the Earth do not expand. |
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Term
| What is it that keeps localized regions of space, such as things on the Earth, planetary systems, star clusters, and whole galaxies from participating in the general expansion of the universe? |
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Definition
| The mutual gravitational attraction between objects in these systems |
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Term
| The cosmic background radiation is.. |
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Definition
| low-intensity radio noise, with a 3 K blackbody temperature, almost uniform in intensity in all directions. |
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Term
| What is the range of the electromagnetic force (the maximum distance over which it acts)? |
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Definition
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Term
| How many fundamental forces are there in nature at the present time under normal conditions? |
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Definition
| Four: strong, weak, electromagnetic, and gravitational |
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Term
| Our view of the universe is a limited one because of what fundamental fact? |
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Definition
| Light from objects farther away than a certain distance, defined by the travel time of light in the lifetime of the universe, has not yet reached us. |
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Term
| What is the difference between dark matter and dark energy? |
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Definition
| Dark matter is attractive and slows the universal expansion, whereas dark energy is repulsive and accelerates the universal expansion. |
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Term
| Knowing Luminosity Classes of stellar objects -- how far is the closest object with these properties: G2V, 1LO, 1MO, 1RO |
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Definition
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