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Astronomy Chapter 1


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
Created by: sgw005