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PHYS 284 Midterm Exam-Questions with Correct Answers/ Verified/ Latest 2024/2025
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PHYS 284 Midterm Exam-Questions with Correct Answers/ Verified/ Latest 2024/2025
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PHYS 284 Midterm Exam-Questions with Correct Answers/Verified/ Latest 2024/2025
star - ✔✔A large, glowing ball of gas that generates heat and light through nuclear fusion in
its core. Our Sun is a star.
planet - ✔✔A moderately large object that orbits a star and shines primarily by reflecting
light from its star. According to the current definition, an object can be considered a planet
only if it (1) orbits a star, (2) is large enough for its own gravity to make it round, and (3) has
cleared most other objects from its orbital path. An object that meets the first two criteria
but has not cleared its orbital path, like Pluto, is designated a dwarf planet.
moon - ✔✔An object that orbits a planet. The term satellite is also used more generally to
refer to any object orbiting another object.
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.
solar system - ✔✔The Sun and all the material that orbits it, including planets, dwarf
planets, and small solar system bodies. Although the term solar system technically refers
only to our own star system (solar means "of the Sun"), it is often applied to other star
systems as well.
star system - ✔✔A star (sometimes more than one star) and any planets and other materials
that orbit it.
galaxy - ✔✔A great island of stars in space, all held together by gravity and orbiting a
common center, with a total mass equivalent to millions, billions, or even trillions of stars.
, galaxy cluster - ✔✔A collection of galaxies bound together by gravity. Small collections (up
to a few dozen galaxies) are generally called groups, while larger collections are called
clusters.
super cluster - ✔✔A gigantic region of space in which many groups and clusters of galaxies
are packed more closely together than elsewhere in the universe.
universe - ✔✔The sum total of all matter and energy—that is, all galaxies and everything
between them.
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.
astronomical unit - ✔✔The average distance between Earth and the Sun, which is about 150
million kilometers. More technically, 1 AU is the length of the semimajor axis of Earth's
orbit.
light year - ✔✔The distance that light can travel in 1 year, which is about 10 trillion
kilometers (more precisely, 9.46 trillion km).
rotation - ✔✔The spinning of an object around its axis. For example, Earth rotates once
each day around its axis, which is an imaginary line connecting the North and South Poles.
orbit - ✔✔The orbital motion of one object around another due to gravity. For example,
Earth orbits the Sun once each year.
expansion - ✔✔The increase in the average distance between galaxies as time progresses.
constellation - ✔✔a region of the sky with well-defined borders; the familiar patterns of
stars merely help us locate the constellations.
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