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
