Details Title: Astro things 1:. Description: N/A Total Flash Cards: 49 Created: 05/28/2009 08:59:52		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 Astronomy Definition the study of the Universe in which humans live Term Planck time Definition smallest measurable unit of time Term Age of the Universe Definition 12 billion years! Term Parsec Definition 3.26 light years Term Radius of an atom Definition 1 angstrom Term How many constellations today? Definition 88; 40 new, 48 are from classical age by Babylonians, Egyptians, Mesopotamians, and Greeks. Term Constellation Definition what used to define a group of stars, now defines a section/area of sky with clear boundaries Term Asterism Definition Groupings of stars, smaller than a constellation. For example: The Big Dipper is an asterism of the constellation Ursa Major. Term Diurnal Motion Definition Daily motion of the sun, moon, planets and stars Term Circumpolar stars Definition means "around the pole"; stars that circle the pole and never set Term Precession Definition radius: 23.5deg; due to the fact that the earth is not a perfect sphere. It's top-like motion. Moves reference marks such as celestial poles. Term Magnitude Scale Definition first appeared in writings of Ptolemy; 1st mag. to 6th mag. 1 mag= 2.5 factor in brightness. Term luminosity of a star Definition inversely related to the square of its distance. If a star is twice as distance, 2^2 is 4...1/4 the luminosity of the first star. Term AU Definition Astronomical Unit; average distance between the earth and sun. (1.5 x 10^11 km Term Eratosthenes Definition first to calculate circum. of earth Term Aristarchus Definition Measured relative sizes of earth/moon/sun; was far off, but established that the sun was far away and larger than earth Term Aristotle Definition geocentric model; traced out the ecliptic Term Equinox Definition anytime the sun crosses the celestial equator, even amount of sunlight per day. Term Vernal Equinox Definition March 21st, our calendar's zero Term Autumnal Equinox Definition September 22/23 Term Sulstice Definition Point where the sun is furthest north or south Term Aphelion Definition furthest from the sun (July 6th) Term Perihelion Definition closest to the sun (Jan 3rd) Term An effect of the tilt of the earth's axis Definition it causes sunlight to be more/less direct, which causes our seasons! Term Sidereal (star) Period Definition orbital period of the moon relative to the stars. 27.3 days Term Synodic period Definition orbital period relative to the sun; time between successive new moons, 29.5 days (has to catch up to the sun, who has moved a degree a day across the sky. Term Solar day Definition defined to be 24 hours. rotates 361 degrees to meet back to the sun after moving across its revolution. Term Sidereal Day Definition relative to the stars, 23 hr. 56min. Term Eclipse Definition only occurs when the line of nodes points toward the sun. Term Tilt between earth and lunar orbital plane: Definition 5degrees Term Amount of eclipses in a year Definition min. 2 and max. 7 in one year Term Penumbra Definition observer sees partial covering of the sun; surrounds the umbra Term Umbra Definition observer sees the sun completely covered, darkest portion of shadow Term antiumbra Definition beyond the apex of the umbra, observer sees partial covering of the sun because the object covering is not large enough; only solar eclipses Term Lunar eclipse Definition occurs when the earth casts its shadow onto the moon; seen by everyone who can see the moon; separated by six months Term Length of Totality during Total Solar Eclipse Definition no more than about 7 minutes Term Length of partial coverage from a Solar Eclipse Definition Can last about two hours Term prominence Definition gas being projected off and back down to the Sun and above the Chromosphere Term Corona Definition The ring of white light emission during total solar eclipse Term Bailey's Beads Definition caused by mountains and valleys on Moon's surface; little rim of sun shining through on the edges Term Annular Eclipse Definition a partial eclipse where it can only be seen through the antiumbra, where there is an annulus, or ring. Term Saros Cycle Definition an eclipse cycle that has a period of about 18 years, 11 days, and 8 hours. Term Ptolemy Definition geocentric, used epicycles, was used for 1400 years, very accurate Term Copernicus Definition heliocentric, still used perfect circular motion, not as accurate as Ptolemy's model Term deferent Definition circle about which an epicycle travels Term equant Definition point about which the epicycle seems to make uniform circular motion about the deferent Term epicycle Definition circle about which planet travels, used to explain motions like retrograde motion Term Almagest Definition Ptolemy's model Term De Revolutionibus Definition Copernican's writing over heliocentricity