Term
| what are the three parts of the milky way galaxy? |
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Definition
| galactic disk, galactic bulge, galactic halo |
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Term
| Our sun lies in a part of the Galazy known as the _____, an immense circular, flattened region containing most of our galxy's luminous stars and interstellar matter lies in the direction of the constellation sagitarrius. |
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| the disk and bulge are embedded ina roughly spherical ball of faint old stars known as the ____. |
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| Two types of pulsating variable stars that have played central roles in revealing both the true extent of our Galaxy and the distances to our galactic neighbors are the______and_____variables. |
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Term
| Stars whose luminosities change significantly over relatively short periods of time--some quite erratically others mor regular: |
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Definition
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Term
| stellar orbits in our galaxy |
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Definition
| stars in the galactix disk move in orderly, circular orbits about the galactic center. In contrast halo stars have orbits with largely random orientations. The orbit of a typical halo star takes it high above the galactic disk, then down through the disk plane , then out the other side and far below the disk The orbital properties of bulge stars are intermediate between those of disk stars and halo stars |
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Term
| milky way galazy formation |
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Definition
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Term
| most of the mass in our galaxy exists in the form of _____, whose gravitational effects we can measure and quantify but who sprecise nature we do not understand. |
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Definition
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Term
| our own milky way galaxy and our neighbor, andromeda are what type of galaxy? |
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Definition
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Term
| Spiral galaxy is denoted by the letter S and classified as type _,_, or_ according to the size of its central bulge. |
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Definition
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Term
| Which glaxy has the largest bulge? |
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Definition
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Term
| the spiral arms are the tightest in a ____galaxy. |
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Definition
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Term
| barred spiral galaxies are denoted ___. and divided into subcategories ____, ___, ___by the size of their bulge. |
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Definition
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Term
| _____have no spiral arms and in most cases no galactic disk. |
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Definition
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Term
| elliptical galaxies are categorized from ___ to____. ____is the most circular. |
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Definition
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Term
| A class of galaxies that show evidence of a thin disk and a flattened bulge yet contain neither loose gas nor spiral arms are called ____is a bar is not present and ____is a bar is present. |
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Term
| What is a famous pair of Irr I galaxies that orbit the milky way galaxy? |
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Term
| The variation in galxy types across the diagram, from ellipticals to spirals to irregulars, is often referred to as the ______. |
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Definition
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Term
| eaily recognizble astronomical objects whose luminosities are confidently known |
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Definition
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Term
| an empirical correlation between rotational velocity and luminosity in spiral galaxies |
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Definition
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Term
| the milky way, andromeda, m33, and several other galaxies join together to form the_____. |
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Definition
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Term
| A group of clusters held togther by their mutual gravitational attraction is called a _____. |
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Term
| the rate at which a galaxy recedes is directly proportional to its distance from us: |
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Definition
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Term
| Jubbles constant denoted by the symbol Ho is ____. |
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Definition
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Term
| a class of astronomical objects who properties lie between those of normal galaxies and those of the most energetic active galaxies known |
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Definition
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Term
| active galaxies that emit large amounts of energy in the radio portion of the electromagnetic spectrum |
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Definition
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Term
| the most luminous objects known |
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Definition
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Term
| a system whose abnormal acitivity is related to violent events occuring in or near the active galactic nucleus |
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Definition
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Term
| largest type of black whole in the galxy |
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Definition
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Definition
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Term
| many luminous galaxies with nonstellar emission are known to be_____, previously normal systems currently characterized by widespread epidosdes of star formation, most likely as a result of interactions with a nieghbor |
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Definition
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Term
| most astronomers have concluded that galxy clusters are themselves clustered, forming titanic agglomerations of matter known as _____. |
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Definition
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Term
| when light from a distant object passes close to a galaxy or cluster of galaxies along the line of sight, the image of teh background object can sometimes be split into two ore more separate images. |
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Definition
| gravitational lensing--check |
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