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93 Cards in this Set
- Front
- Back
total solar eclipse
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a solar eclipse during which the Sun becomes fully blocked by the disk of the Moon
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focus (of an ellipse)
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one of two special points within an ellipse that lie along the major axis; when one object orbits a second object, the second object lies at one focus of the orbit
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arcseconds
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one arcsecond is 1/60 of an arcminute
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analemma
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the figure eight path traced by the Sun over the course of a year when viewed at the same place and the same time each day; represents the discrepancies between apparent and mean solar time
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north celestial pole
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the point on the celestial sphere directly above the Earth's North Pole
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science
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the search for knowledge that can be used to explain or predict natural phenomena in a way that can be confirmed by rigorous observations or experiments
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constellation
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a region of the sky
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scientific theory
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a model of some aspect of nature that has been rigorously tested and has passed all tests to date
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pseudoscience
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something that purports to be science or may appear to be scientific but does not adhere to the testing and verification requirements of the scientific method
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lunar phase
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describes the appearance of the Moon as seen from Earth
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longitude
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the angular east-west distance between the prime meridian and a location on the Earth's surface
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annular solar eclipse
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a 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 (or annulus) of sunlight is still visible around the Moon's disk
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meridian
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a half-circle extending from your horizon due south, through your zenith, to your horizon due north
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eclipse seasons
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periods during which lunar and solar eclipses can occur because the modes of the Moon's orbit are nearly aligned with the Earth and Sun
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antimatter
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refers to any particle with the same mass as a particle of ordinary matter but whose other basic properties are precisely opposite
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DNA
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the molecule that represents the genetic material of life on Earth
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precession
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the gradual wobble of the axis of a rotating object around a vertical line
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aphelion
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the point at which an object orbiting the Sun is farthest from the Sun
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altitude (above horizon)
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the angular distance between the horizon and an object in the sky
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Arctic Circle
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the circle on the Earth with latitude 66.5 degrees N
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winter solstice
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the point on the celestial sphere where the ecliptic is farthest south of the celestial equator; the moment in time when the Sun appears at that point each year (December 21)
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Ptolemaic model
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the geocentric model of the universe developed by Ptolemy in about 150 AD
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axis tilt
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the amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane
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Copernican revolution
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the dramatic change that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe
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carbon dioxide cycle
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the process that cycles carbon dioxide between the Earth's atmosphere and surface rocks
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arcminutes
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one arcminute is 1/60 of a degree
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geocentric model
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any of the ancient Greek models that were used to predict planetary positions under the assumption that Earth lay in the center of the universe
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paradigm
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refers to general patterns of thought that tend to shape scientific beliefs during a particular time period
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altitude (above horizon)
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the angular distance between the horizon and an object in the sky
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Arctic Circle
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the circle on the Earth with latitude 66.5 degrees N
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winter solstice
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the point on the celestial sphere where the ecliptic is farthest south of the celestial equator; the moment in time when the Sun appears at that point each year (December 21)
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Ptolemaic model
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the geocentric model of the universe developed by Ptolemy in about 150 AD
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axis tilt
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the amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane
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Copernican revolution
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the dramatic change that occurred when we learned that Earth is a planet orbiting the Sun rather than the center of the universe
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carbon dioxide cycle
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the process that cycles carbon dioxide between the Earth's atmosphere and surface rocks
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arcminutes
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one arcminute is 1/60 of a degree
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geocentric model
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any of the ancient Greek models that were used to predict planetary positions under the assumption that Earth lay in the center of the universe
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paradigm
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refers to general patterns of thought that tend to shape scientific beliefs during a particular time period
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horizon
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a boundary that divides what we can see from what we cannot see
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ecliptic
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the Sun's apparent annual path among the constellations
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eccentricity
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a measure of how much an ellipse deviates from a perfect circle; the center-to-focus distance divided by the length of the semimajor axis
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spring equinox
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the point in Pisces on the celestial sphere where the ecliptic crosses the celestial equator; the moment in time when the Sun appears at that point each year (March 21)
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eclipse
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occurs when one astronomical object casts a shadow on another or crosses our line of sight to the other object
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perihelion
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the point at which an object orbiting the Sun is closest to the Sun
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angular size (distance)
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a measure of the angle formed by extending imaginary lines outward from our eyes to span an object
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celestial navigation
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navigation on the surface of the Earth accomplished by observations of the Sun and stars
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Kepler's first law
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states that the orbit of each planet about the Sun is an ellipse with the Sun at one focus
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apparent retrograde motion
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the 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 sky
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celestial equator
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the extension of the Earth's equator onto the celestial sphere
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focus
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the point at which rays of light that were initially parallel converge
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partial solar eclipse
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a solar eclipse during which the Sun becomes only partially blocked by the disk of the Moon
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fossil
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any relic of an organism that lived and died long ago
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celestial coordinates
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the coordinates of right ascension and declination that fix an object's position on the celestial sphere
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Kepler's laws of planetary motion
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three laws discovered by Kepler that describe the motion of the planets around the Sun
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retrograde motion
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motion that is backward compared to the norm
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ellipse
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a type of oval that happens to be the shape of bound orbits
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nodes
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the two points in the Moon's orbit where it crosses the ecliptic plane
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solar eclipse
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occurs when the Moon's shadow falls on the Earth, which can occur only at new moon
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scientific method
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an organized approach to explaining observed facts through science
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fall equinox
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the point in Virgo on the celestial sphere where the ecliptic crosses the celestial equator; the moment in time when the Sun appears at that point each year (September 21)
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south celestial pole
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the point on the celestial sphere directly above the Earth's South Pole
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circumpolar star
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a star that always remains above the horizon for a particular latitude
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lunar eclipse
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occurs when the Moon passes through the Earth's shadow, which can occur only at full moon
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theory of evolution
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the theory that explains how evolution occurs through the process of natural selection
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prime meridian
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the meridian of longitude that passes through Greenwich, England, defined to be longitude 0 degrees
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local sky
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the sky as viewed from a particular location on Earth; objects in the local sky are pinpointed by the coordinates of altitude and azimuth (direction)
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stellar parallax
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the apparent shift in the position of a nearby star that occurs as we view the star from different positions in the Earth's orbit of the Sun each year
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penumbral lunar eclipse
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a lunar eclipse in which the Moon passes only within the Earth's penumbral shadow and does not fall within the umbra
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apparent solar time
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time measured by the actual position of the Sun in your local sky defined so that noon is when the Sun is on the meridian
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partial lunar eclipse
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a lunar eclipse in which the Moon becomes only partially covered by the Earth's umbral shadow
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zenith
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the point directly overhead which has an altitude of 90 degrees
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saros cycle
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the period over which the basic pattern of eclipses repeats (about 18 years and 11 1/3 days)
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Kepler's third law
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the square of a planet's orbital period is proportional to the cube of its average distance from the Sun (semimajor axis); tells us that more distant planets move more slowly in their orbits
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latitude
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the angular north-south distance between the Earth's equator and a location on the Earth's surface
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Drake Equation
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an equation that lays out the factors that play a role in determining the number of communicating civilizations in our galaxy
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semimajor axis
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half the distance across the long axis of an ellipse (average distance of an orbiting object)
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Metonic cycle
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the 19 year period over which the lunar phases occur on the same dates
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habitable world
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a world with environmental conditions under which life could potentially arise or survive
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model
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a representation of some aspect of nature that can be used to explain and predict real phenomena without invoking myth, magic or the supernatural
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geological time scale
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the time scale used by scientists to describe major eras in Earth's past
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evolution
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the gradual change in populations of living organisms responsible for transforming life on Earth from its primitive origins to the great diversity of life today
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direction
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one of the two coordinates needed to pinpoint an object in the local sky; the direction in which you must face to see the object
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geocentric universe
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the idea that the Earth is the center of the entire universe
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hypothesis
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a tentative model proposed to explain some set of observed facts, but which has not yet been rigorously tested and confirmed
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total lunar eclipse
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a lunar eclipse in which the Moon becomes fully covered by the Earth's umbral shadow
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totality
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the portion of either a total lunar eclipse during which the Moon is fully within the Earth's umbral shadow or a total solar eclipse during which the Sun's disk is fully blocked by the Moon
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habitable zone
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the region around a star in which planets could potentially have surface temperatures at which liquid water could exist
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celestial sphere
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the imaginary sphere on which objects in the sky appear to reside when observed from Earth
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umbra
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the dark central region of a shadow
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Antarctic Circle
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the circle on the Earth with latitude 66.5 degrees S
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penumbra
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the lighter, outlying regions of a shadow
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summer solstice
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the point on the celestial sphere where the ecliptic is farthest north of the celestial equator; the moment in time when the Sun appears at that point each year (June 21)
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zodiac
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the constellations on the celestial sphere through which the ecliptic passes
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