| Question |
Answer |
| geocentric |
an earth-centered universe |
| cosmic address |
place of earth in the universe |
| galaxy |
great island of stars in space |
| Milky Way |
galaxy in which our solar system resides |
| Local Group |
a group of galaxies |
| galaxy clusters |
galaxies with more than a few dozen members |
| super cluster |
a region of tightly packed galaxies |
| universe |
the sum total of all matter and energy |
| expanding |
average distances between galaxies increase with time |
| Big Bang |
the beginning of expansion - 14 billion years ago |
| nuclear fusion |
the process by which atomic nuclei smash together to make a heavier nuclei |
| supernova |
titanic explosion in which a star dies |
| early universe |
made up of hydrogen and helium |
| age of the solar system |
4.5 billion years |
| speed of light |
300,000 km per sec |
| light year |
distance light travels in a year - 6 trillion miles |
| brightest star |
Sirius |
| fact of light |
the farther away we look in distance, the further back we look in time |
| Orion Nebula |
a giant cloud in which stars and planets are forming |
| Andromeda Galaxy |
closest galaxy - 2.5 million light years |
| age of universe |
14 billion years |
| observable universe |
the portion of the universe that we can observe |
| definition of planet |
1) orbits around a star
2) round shape
3) clear neighborhood around orbit |
| number of stars |
more than 100 billion |
| speed of Earth |
600 miles per hour |
| astronomical unit |
Earth's average orbital distance - 93 million miles |
| ecliptic plane |
a flat plane defined by the Earth's orbital path |
| axis tilt |
23.5 degrees |
| Polaris |
name for the North Star |
| speed of solar system |
500,000 miles per hour |
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