Chapter 1 - Modern View of the Universe Flashcards
Light-year
The distance light can travel in one year (10 trillion km or 6 trillion mi)
Local Group
The group of about 40 galaxies of which the Milky Way is included
Universe
The sum total of all matter and energy
Observable universe
The portion of the entire universe that we can potentially observe
AU
Astronomical Unit - Earth’s average distance from the Sun (about 150 million km or 93 million mi)
As viewed from above the North Pole, what direction does Earth rotate?
West to east, or counterclockwise
Ecliptic plane
The plane of Earth’s orbital path
The Earth’s axis is tilted by how many degrees from a line perpendicular to the ecliptic plane?
23.5°
Diameter of Sun
1,400,000km
Earth-Moon distance
384,000km
Diameter of Earth
12,800km
Outer solar system
Generally considered to encompass the region of our solar system beginning at about the orbit of Jupiter
Asteroid
A relatively small and rocky object that orbits a star; asteroids are officially considered part if a category known as “small solar system bodies”
Galaxy
A huge collection of anywhere from a few hundred million to more than a trillion stars, all bound together by gravity
Local Cluster
The supercluster of galaxies to which the Local Group belongs
