CP 1 A Modern View of the Universe Flashcards
What is a star
A large, glowing ball of gas that generates heat and light through nuclear fusion
What is a planet
A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition.
what is a moon
AN object that orbits a planet
what is a comet
A relatively small and icy object that orbits a star
what is a solar system
A star and all the material that orbits it, including its planets and moons
what is a nebula
- An interstellar cloud of gas and/or dust
- a star forming region
What is an AU
average distance between the Earth and the
Sun (150 million kilometers)
what is a light year
The distance that light can travel in 1 year
what is a galaxy
A great island of stars in space, all held together by gravity and orbiting a common center
what is a galaxy group
A gravitationally bound
group of up to a few dozen galaxies,
typically a few million light years across
what is a galaxy cluster
Galaxy Cluster A group of a few hundred
to a few thousand galaxies
how can we know what the universe was like in the past
Light travels at a finite speed (300,000 km/s).
Thus, we see objects as they were in the past: The farther away we look in distance,
the further back we look in time
statement:
At great distances, we see objects as they were when the universe was much younger.
how old is the universe
14 billion years old
TF the universe is expanding
T
