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Astronomy Week 1
Astronomy
| Term | Definition |
|---|---|
| solar system | sun, planets, moons, asteroids, comets |
| galaxy | ie. Milky Way, great island of stars in space, held together by gravity orbiting a common center |
| Local group | more than 70 galaxies. Our galaxy is the second largest |
| galaxy clusters | groups of galaxies with many more large members |
| superclusters | clusters of galaxy clusters |
| cosmos/universe | sum total of all matter and energy, superclusters and voids |
| astronomical unit | Earth's average distance from the sun, about 150 million km |
| light-year | distance light can travel in one year, 10 trillion km/6 trillion miles |
| light-second | distance, 300,000 km |
| planet | 1) orbits a star 2)large enough for its own gravity to make it round 3) has cleared most other objects from its orbital path (if it doesn't fulfill #3, it's a dwarf planet) |
| moon/satellite | object that orbits a planet |
| asteroid | small + rocky object that orbits a star |
| comet | small and ice-rich object that orbits a star |
| small solar system body | object that orbits a star but is too small to qualify as a planet/dwarf planet |
| star system | star and any planets/other materials that orbit it |
| observable universe | portion of the entire universe that can be seen from Earth. Probably only a tiny portion of the entire universe. |
| rotation | spinning of an object around its axis. Earth rotates around its axis daily. |
| orbit/revolution | orbital motion of one object around another due to gravity. Earth orbits the sun once a year. |
| expansion (of the universe) | increase in the avg distance between galaxies as time progresses |
| big bang | 14 billion years ago, created universe |
| nuclear fusion | process, lightweight atomic nuclei smash together and fuse |
| cosmic calendar | 14 billion year history of universe compressed into one year. Our lifetimes are fractions of a second. |
| ecliptic plane | flat plane defined by earth's orbital path |
| axis tilt | axis of Earth points to Polaris, 23.5 degrees from a line perpendicular to the ecliptic plane |
| dark energy | getting faster |
| doppler shifts | how we measure galaxy speeds, spread light into spectra and observe ___ |
| hypothesis | educated guess |
| paradigm | general pattern of thought |
| theory | powerful model, tested and verified so we have high confidence in its validity |
Created by:
mglen
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