astronomy exam one – Flashcards
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astronomical unit
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average distance of earth from the sun
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Light year
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the distance that light, moving at a constant speed of 300,000 km/s, it travels in one year. One light year is about 10 trillion km.
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parsec
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the distance at which star must lie in order for its measured parallax to be exactly one arc second; 1 parsec equals 206,000 AU.
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celestial sphere
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imaginary sphere surrounding earth to which objects in the sky were once considered.
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Moon
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small body in orbit around the planet
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planet
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one of eight major bodies that orbit the sun, visible to us by reflected sunlight
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Star
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a glowing ball of gas held together by tone gravity and powered by nuclear fusion at its core., a huge ball of very hot gases in space
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solar system
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Sun and All the bodies that orbit it
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galaxy
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gravitationally bound collection of the large number of stars. The sun is a star in the Milky Way galaxy
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universe
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the totality of all space, Time, matter, and energy
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Summer solstice
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point on the ecliptic where the sun is at its northernmost point above the celestial equator, occurring on or near June 21, When the sun is at its northernmost point from the equator in the Northern Hemisphere; the day is the longest (usually June 21st or 22nd)
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winter solstice
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point on the ecliptic where the sun is at its southernmost point below the celestial equator are occurring on or near December 21
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equinox
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Date on which the sun crosses the celestial equator moving northward occurring on or near March 21 --The South word occurring on or near September 22, either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length
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ecliptic plane
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the plane of the Earth's orbit around the Sun
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new moon
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Phase of the moon during which none of the lunar disk is visible
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full moon
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Phase of the moon in which it appears as a complete circular disc in the sky
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crescent moon
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appearance of the moon when less than half of the body's hemisphere is visible from Earth
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Quarter moon
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lunar phase in which the moon appears as a half desk
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gibbous moon
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appearance of the moon when more than half but not all Of the body's hemisphere is visible from Earth
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lunar eclipse
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celestial events during which the moon passes for through the shadow of earth, temporarily darkening its surface
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solar eclipse
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celestial events during which the new moon passes directly between Earth and the sun temporarily blocking the sun's light
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totality
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The period during a total solar eclipse when the disk of the Sun is completely hidden.
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geocentric
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a model of the solar system that holds the Earth is at the center of the Universe and bodies are in orbit around it. The earliest theories of the solar system were geocentric, followed by Aristotle and Ptolemy
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heliocentric
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a model of the solar system that is centered on the sun, with the earth and motion around the sun. Followed by Copernicus, Tycho ,and Kepler, and Galileo
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aphelion
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The point On the elliptical path of an object in orbit around the sun, that is the most distant from the Sun
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perihelion
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the closest approach To the son of any object in orbit around it, orbital point nearest the sun
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elliptical
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(Ellipse) Not a perfect circle, oval
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orbital eccentricity
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the shape of a planet's orbit around the sun, a measure of the flatness of an ellipse, equal to the distance between the two foci divided by the length of the major axis. Circle= 0 and ellipse= 1.
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wavelength
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The distance from one Wavecrest to the next, at a given instant in time
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photon
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individual packets of electromagnetic energy that makes up electromagnetic radiation
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atom
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building block of the matter, composed of the positively charged protons and Neutral neutrons in the nucleus surrounded by negatively charged electrons
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nucleus
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dense, central region of an atom containing both protons and neutrons and orbited by one or more electrons
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proton
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an elementary particle carrying a positive electric charge, a component of all atomic nuclei.
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Neutron
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an elementary particle with roughly the same mass of the proton, but which is electrically neutral
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electron
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in elementary particle with negative electric charge, one of the components of an atom
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ion
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and atom that has lost one or more of its electrons
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atomic elements
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Elements that exist in nature with single atoms as their basic units.
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blackbody
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the characteristic way in which the intensity of radiation emitted by a Hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object.
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spectrum absorption
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dark lining in an otherwise continuous bright spectrum, where lights within one narrow frequency range has been removed
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spectrum emission
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bright line in a specific location of the spectrum of radiating material, corresponding to a mission of lights at a certain frequency. A heated gas in a glass container produces emission lines in its spectrum.
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continuum
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n. a continuous whole without clear division into parts
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refractor/refracting telescope
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a telescope that uses a lens to gather and focus light from a distant object
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reflector/reflecting telescope
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a telescope that uses a mirror to gather and focus light from a distant object
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chromatic aberration
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The tendency for lens to focus red and blue lights differently, causing images to become blurred
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light -- gathering power
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amount of light telescope can view and focus, Proportional to the area of the primary mirror
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angular resolution
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the ability of the telescope to distinguish between adjacent objects in the sky
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resolving power
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A measure of the clarity of an image; the ability of an optical instrument to show two objects as separate.
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seeing
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a term used to describe the ease with which the telescope observations can be made from Earth's surface, giving the blurring effects of atmospheric turbulence
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Kepler's first law addresses shape of the planetary orbit
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the orbital path of the planets are elliptical ( not necessarily circular ), with the sun at one focus
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Kepler's second law addresses the speed at which a planet traverses different parts of its orbit
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and imaginary line connecting the sun to any planet sweeps out equal areas of the ellipse in equal intervals of time