Terms for Earth Science Chapter 1 Activity 1 (Book 2)
Terms
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- astronomical unit
- a unit of measurement equal to the average distance between the Sun and Earth
- light-year
- a unit of measurement equal to the distance light travels in one year
- parsec
- a unit used in astronomy to describe large distance, such as the widths of galaxies
- nebula
- a cloud of gas and dust that was probably cast off from other stars that once were in our region of the galaxy
- Nebular Theory
- the idea that the solar system evolved from such a swirling cloud of dust (nebula)
- constellation
- a grouping of stars in the night sky that fall into a recognizable pattern
- planetesimal
- a small body formed from the solar nebula and eventually grew into protoplanetary bodies
- protoplanetary body
- a clump of material fromed from planetetesimals of the early stages of solar system formation that were the forerunner of today's planets
- nuclear fusion
- a nuclear proccess that releases energy when lightweight nuclei combine to form heavier nuclei during which hydrogen atoms fused to create helium atoms
- terrestrial planets
- [Mercury, Venus, Earth, and Mars] planets formed in the inner part of the solar system, consisting of mainly rocky materials
- gas giant planets
- [Jupiter, Saturn, Uranus, and Neptune] planets formed in the outer part of the solar system, composed mostly of hydrogen, helium, and methane, and having a density less than 2 gm/cm^2
- comet
- a chunk of frozen gases, ice, and rocky debris that orbits the sun found mainly in the outer solar system
- asteroid
- a small planetary body in orbit around the Sun that is larger than a meteoroid but smaller than a planet that are commonly found between the orbits of Mars and Jupiter
- Milky Way
- our gallaxy: gallaxies are classified according to their shape; elliptical, spiral, or irregular
- AGES
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Solar System - 4.5 billion years
Milky Way Galaxy - 10 billion years
Universe - 12 to 14 billion years