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chapter 18 (i think) the one that says chapter test a : studying spacemonth


created a sun-centered theory of the universe


proved that there were many galaxies


showed that gravity keeps planets and moons in orbit


created an earth-centered theory of the universe


showed that planets move in elliptical orbits around the sun


was one of the first astronomers to use a telescope to observe in space


roughly, the time required for the moon to orbit once around the earth

refracting telescope

an instrument that uses a set of lenses to focus light


the angle between an object in the sky and the horizon


the time required for the earth to rotate once on its axis


the line where the sky and the earth appear to meet


a region of the sky that contains a recognizable


the time required for the earth to orbit once around the sun


the apparent path of the sun across the celestial sphere as seen from earth


one can tell how far north or south an object is from the celestial equator by the object's _______

celestial sphere

the imaginary sphere, created by scientists, that surrounds the earth

electromagnetic spectrum

all of the wavelengths of electromagnetic radiation

In Space

where scientists put telescopes to avoid interference from earth's atmosphere


an imaginary point directly above an observer's head.

the very large array

the largest telescope.

right ascension

the vernal equinox is used to establish a star's_____

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