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astr 101 chp 1
the cosmic perspective 6ed author Bennett
All planets are made of rock and all stars are made of gas.
Which of the following is not a general difference between a planet and a star?
the Sun and all the objects that orbit it
Our solar system consists of _________.
collection of a few hundred million to a trillion or more stars, bound together by gravity
A typical galaxy is a _________.
The sum total of all matter and energy
Which of the following best describes what we mean by the universe?
The event that marked the beginning of the expansion of the universe
What do astronomers mean by the Big Bang?
Average distances between galaxies are increasing with time.
What do we mean when we say that the universe is expanding?
14 billion years
Based on observations of the universal expansion, the age of the universe is about _________.
it uses "light-years" to talk about time, but a light-year is a unit of distance
A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
that portion of the universe that we can see in principle, given the current age of the universe
The term observable universe refers to _________.
small enough to fit within your hand
On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
About the distance across the United States
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
a few hundred billion
The number of stars in the Milky Way Galaxy is approximately _________.
the average distance between Earth and the Sun
An astronomical unit (AU) is _________.
The plane of Earth's orbit around the Sun
What is the ecliptic plane?
How long does it take the Earth to complete one orbit around the Sun?