Term Definition
astronomy the study of all physical objects beyond earth
astronomer someone who studies space/heavens
revolution the elliptical motion of a body as it orbits another body in space
rotation the spinning motion of a body on its axis
orbit the elliptical path a body takes as it travels around another body; the motion itself
calendar/gregorian a system for organizing time
year the time required for the earth to orbit the sun once
month the time required for the moon to orbit the earth once
day the time required for the earth to rotate once on its axis
heliocentric sun centered
geocentric earth centered
astrolabe handheld tool invented by the arabs used to measure the stars
horizon the line where the sky and earth appear to meet
zenith an imaginary point in the sky directly above an observer on earth
altitude the angle between the object and the horizon
azimuth imaginary circle that forms exactly around the horizon at 360 degrees
celestial sphere stars in a sphere shape around earth
declination a measure of how far north or south an object is from the celestial equator
right ascension measure of how far east an object is from the point at which the sun appears on the first day of spring
telescope instrument that collects electromagnetic radiation from the sky and concentrates it for better observation
optical telescope telescope that collects visible light for closer observation
electromagnetic radiation radiation from the sun
star maps circular maps the marked stars by hemisphere
astronomical unit way to measure units to planets (sun to planet)
light year distance light travels in a year (6 trillion miles/year)
big bag theory the theory that states the universe began with a tremendous explosion
nebula a large cloud of dust and gas in interstellar space (where stars are formed)
solar system the system composed of the sun and the planets and other bodies that travel around the sun
galaxy a large grouping of stars in space
star huge, hot, brilliant balls of fire
planet celestial body that orbits a star
moon natural satellite
asteroid small, rocky body that revolves around the sun
meteoroid small, rocky body orbiting the sun
meteorite meteoroid that strikes earths ground
meteor when meteoroid moving towards earth at a fast pace and light comes off of it
fusion energy from a star
satellite a natural or artificial body that revolves around a planet
space probe a vehicle that carries scientific instruments to planets or other bodies in space
comet planetesimals made of ice, 'dirty snowballs'
seasons 4 divisions, weather patterns/daylight hours
tilt cause to move into a sloping position
planetesimals the tiny building blocks of the planets that formed as dust particles stuck together and grew in size

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