Sept. 4th - Basics Flashcards
Solar System:
Sun, planets, their moons, and smaller objects like asteroids and comets
Galaxy:
great island of stars in space, held together by gravity and orbiting a common center
Galaxy Clusters:
groups of galaxies with many more large members
Superclusters
the regions in which galaxies and galaxy clusters are most tightly packed; essentially, clusters of galaxy clusters
Universe:
made up of all of the above structures (i.e. galaxy, galaxy clusters, superclusters); the sum of all matter and energy, encompassing the superclusters and voids and everything in them
Astronomical Unit:
Earth’s average distance from the Sun - about 150 million kilometers; commonly used to describe distances within our solar system
Light year:
Distance that light can travel in 1 year - about 10 trillion kilometers; commonly used to describe distances of stars and galaxies (UNIT OF DISTANCE, NOT TIME)
- One light second is 300,000 km, one light year is 10 trillion kilometers in 1 year
Star
a large, glowing ball of gas that generates heat and light through nuclear fusion in its core
Planet:
a moderately large object that orbits a star and shines primarily by reflecting light from its star
An object can only be considered a planet only if it…
a) orbits a star
b) is large enough for its own gravity to make it round
c) has cleared most other objects from its orbital path
- Objects that satisfy only a) and b) are deemed dwarf planets, like pluto
Exoplanet:
a planet orbiting a star other than our sun
Moon:
an object that orbits a planet
Asteroid:
a relatively small and rocky object that orbits a star
Comet
a relatively small and ice-rich object that orbits a star
Small Solar System Body
an asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet
World
in the context of astronomy, any planet, dwarf planet, moon, or small body we could imagine visiting
Star System
a star, and any planets and other materials that orbit it
Observable Universe
the portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the entire universe.
Rotation
the spinning of an object around its axis
Orbit
the orbital motion of one object around another due to gravity
Expansion
the increase in the average distance between galaxies as time progresses
Earth moves from…
west to east (counter clockwise), so you’ll see stars move from east to west
Earth’s orbital path defines the ecliptic plane:
axis tilt of 23.5 degrees from a line perpendicular to the ecliptic plane, and remains pointed in the SAME DIRECTION throughout the year
