| A | B |
|---|
| time required for the earth to orbit once around the sun | year |
| amount of time required for the moon to orbit once around the earth | month |
| time required for the earth to rotate once on its axis | day |
| created a sun-centered theory of the universe | Copernicus |
| proved that there were many galaxies | Hubble |
| showed that gravity keeps planets and moons in orbit | Newton |
| created an earth-centered theory of the universe | Ptolemy |
| showed that planets move in elliptical orbits around the sun | Kepler |
| scientist who used a telescope to observe objects in space | Galileo |
| HR diagram shows this relationship | temperture and absolute magnitude |
| stars formed from a supernova | black hole and neutron star |
| shape of the Milky Way | spiral |
| path each planet moves around the sun | ellipse |
| formed from matter closer to the center of the nebula | inner planets |
| holds a nebula together | inward force of gravity and outward pressure |
| direction our universe is moving | outward |
| Where do new stars form from? | old stars |
| a small, hot, dim star that is the leftover center of an old star | white dwarf |
| a gigantic explosion that causes the death of a large star | supernova |
| a star in which the electrons and protons have become neutrons | neutron star |
| a star that expands and cools once it runs out of hydrogen | red giant |
| a spinning neutron star that emits rapid pulses of radio and optical energy | pulsar |
| a massive and dense object from which even light cannot escape its gravity | black hole |
