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The Essential Cosmic Perspective - Chapter 2 Flashcards

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3714419343constellationa region of the sky with well-defined borders0
3714421094celestial spherethe illusion that all stars lie on the edge of a sphere around Earth that occurs because we lack depth perception1
3714425267north celestial polethe point directly above Earth's North Pole2
3714431491south celestial polethe point directly above Earth's South Pole3
3714432914celestial equatora projection of Earth's equator into space, which makes a complete circle around the celestial sphere4
3714435533eclipticthe path the Sun follows as it appears to circle around the celestial sphere once each year5
3714438880local skythe sky as seen from where you happen to be standing6
3714440575horizonthe boundary between Earth and the sky7
3714442304zeniththe point directly overhead in the sky8
3714443891meridianan imaginary half-circle stretching from the horizon due south, through the zenith, to the horizon due north9
3714447356direction (local sky)one of the two coordinates needed to pinpoint an object in the local sky10
3714449621altitudethe angular distance between the horizon and an object in the sky11
3714451180angular size (or angular distance)a measure of the angle formed by extending imaginary lines outward from our eyes to span an object (or the space between two objects)12
3714451870arcminute1/60 of 1 degree13
3714451871circumpolar stara star that always remains above the horizon for a particular latitude14
3714451872latitudethe angular north-south distance between Earth's equator and a location on Earth's surface15
3714452803longitudethe angular east-west distance between the prime meridian and a location on Earth's surface16
3714454158prime meridianthe meridian of longitude that passes through Greenwich, England; defined to be longitude 0 degrees17
3714454159zodiacthe constellations on the celestial sphere through which the ecliptic passes18
3718896318June solsticethe moment when the Northern Hemisphere is tipped most directly toward the Sun and receives the most direct sunlight19
3718896319December solsticethe moment when the Northern Hemisphere receives the least direct sunlight20
3718896989March equinoxthe moment when the Northern Hemisphere goes from being tipped slightly away from the Sun to being tipped slightly toward the Sun21
3718897943September equinoxthe moment in when the Northern Hemisphere first starts to be tipped away from the Sun22
3718897944precessionthe gradual wobble of the axis of a rotating object around a vertical line23
3718898996lunar phasesthe state determined by the portion of the visible face of the Moon that is illuminated by sunlight; cycles through waxing crescent, first-quarter, waxing gibbous, full, waning gibbous, third-quarter, waning crescent, and back to new24
3718900954synchronous rotationthe rotation of an object that always shows the same face to an object that it is orbiting because its rotation period and orbital period are equal25
3718900955eclipsean event in which one astronomical object casts a shadow on another or crosses our line of sight to the other object26
3718902024lunar eclipsean event that occurs when the Moon passes through Earth's shadow, which can occur only at full moon27
3718902025solar eclipsean event that occurs when the Moon's shadow falls on Earth, which can occur only at a new moon28
3718902026nodesthe two points in the Moon's orbit where it crosses the ecliptic plane29
3718902027umbrathe dark central region of a shadow30
3718904174penumbrathe lighter, outlying regions of a shadow31
3718904175total lunar eclipsea lunar eclipse in which the Moon becomes fully covered by Earth's umbral shadow32
3718904812partial lunar eclipsea lunar eclipse during which the Moon becomes only partially covered by Earth's umbral shadow33
3718904813penumbral lunar eclipsea lunar eclipse during which the Moon passes only within Earth's penumbral shadow and does not fall within the umbra34
3718906356totalitythe portion of a total lunar eclipse during which the Moon is fully within Earth's umbral shadow or a total solar eclipse during which the Sun's disk is fully blocked by the Moon35
3718906357total solar eclipsea solar eclipse during which the Sun becomes fully blocked by the disk of the Moon36
3718907763annular eclipsea solar eclipse during which the Moon is directly in front of the Sun but its angular size is not large enough to fully block the Sun; thus, a ring of sunlight is still visible around the Moon's disk37
3718907764partial solar eclipsea solar eclipse during which the Sun becomes only partially blocked by the disk of the Moon38
3718910329saros cyclethe period over which the basic pattern of eclipses repeats, which is about 18 years and 11 1/3 days39
3718910889apparent retrograde motionthe apparent motion of a planet, as viewed from Earth, during the period of a few weeks or months when it moves westward relative to the stars in our sky40
3718912901stellar parallaxthe apparent shift in the position of a nearby star (relative to distant objects) that occurs as we view the star from different positions in Earth's orbit of the Sun each year41

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