study exam 3 ast
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Valencia College *
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Course
1002
Subject
Astronomy
Date
Apr 3, 2024
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docx
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3
Uploaded by HighnessOtter11079
A spiral density wave in a Galaxy refers to - a slight "bunching together" of the stars and
gas in the spiral arms of a disk galaxy, causing a large increase in the local star formation rate.
dark energy is probably made up of - a phenomenon that may be revealed by a good enough theory of quantum
During the particle era soon after the Big Bang, particles and their antiparticles were constantly being created and destroyed in a process called - annihilation
Elliptical galaxies - have no obvious galactic disk and contain mostly old, halo-type stars.
from the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that - the universe is expanding
From the fact that virtually every galaxy is moving away from us and more distant galaxies are moving away from us at a faster rate than closer ones, we conclude that - the universe is expanding
Given that white dwarf supernovae are such good standard candles, why don't we use them to measure the distance to all galaxies? - they are rare events, so we have observed them in only a tiny fraction of all galaxies
how can we tell the age of the universe? - by using the inverse of the Hubble's constant
how do we know that quasars are no larger than the solar system? - they vary in brightness on a timescale of days
how do we know that quasars are no larger than the solar system? - they vary in brightness on a timescale of days
how would you expect a star that formed recently in the disk of the galaxy to differ from one that formed early in the history of the disk? - it should contain a higher fraction of elements heavier than hydrogen and helium
Hubble's law tells us that - more distant galaxies are receding from us faster than nearby galaxies
if observations had shown that the cosmic microwave background was perfectly smooth
( rather than having very slight variations in temperature). then we would have no way to account for _____ - how galaxies came to exist
if we make the simple assumption that the current expansion rate of the universe has and will remain constant, what is the age of the universe? - 14 billion years
in spiral galaxies, why do the spiral arms appear brighter than the areas between the arms? - there are more bright stars in the spiral arms because they formed there and are short-lived, so they never move out the spiral arms
in the milky way, we see two main populations of stars. which of the following statements about these populations is TRUE? - disk stars tend to have a heavy element
content similar to the Sun
Is space within clusters of galaxies expanding according to Hubble's law? - no, because
their gravity is strong enough to hold them together even when the universe as a whole expands.
is space within clusters of galaxies expanding according to hubble's law? - no, because their gravity is strong enough to hold them together even while the universe as a whole expands
list several distance measuring techniques in order of their distance determining ability, from the most nearby objects to the most distant objects? - stellar parallax, spectroscopic parallax, variable stars, Tully-Fisher, Hubble law
most of the mass of a galaxy is contained in - dark matter of the galaxy
Olbers' paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question? - why is the sky dark at night?
Powerful jets coming from active galactic nuclei are sometimes seen to fly away from their driving source at apparent speeds much faster than light. This is due to - a relativistic illusion
the amount of normal matter in the Universe (i.e., people, planets, and stars) is roughly ___ of the total mass-energy density of the Universe? - 5%
the Big Bang theory predicts the relative abundances of various elements created during the era of nucleosynthesis, and these have been confirmed by observations. the abundance ( by mass) are about - 75\ % hydrogen, 25\% helium, and 0.001\% deuterium
the cosmic microwave background refers to - the leftover radiation from the Big Bang, last emitted at the end of the era of nuclei, and redshifted into the microwave part of the electromagnetic spectrum
the Fermi paradox, named after the early 20th century physicist Enrico Fermi, refers to -
his question "where are they?" about the lack of evidence fro extraterrestrial civilizations
the GUT force in the early universe operated as a unification of the _____ forces at high
temperatures - strong and electroweak
the large and small magellanic clouds, which are small, satellite galaxies of the milky way, are examples of what kind of galaxy? - irregular galaxies
the milky way is - an isolated large system of billion stars
the rotation curve ( rotation velocity vs. distance from center) for objects in our Galaxy - is flat and remains flat at radii beyond the visible edge of the Galaxy indicating that significant dark matter is present.
what are the ways we can tell that galaxy cluster contain large amounts of dark matter? - all three methods
what did Carl Sagan mean when he said that we are all "star stuff"? - that the carbon, oxygen, and other elements essential to life were created by nucleosynthesis in stellar cores
what do astronomers currently think is at the center of the milky way galaxy - a massive black hole
what evidence supports the existence of a black hole at the center of our galaxy? - the motions of the gas and stars at the center indicate that it contains 4 million solar masses
within a region only 3 light-years across.
What is powering an Active Galaxy? - accretion onto a supermassive black hole
what is the age distribution observed for stars in various regions of our galaxy? - most stars in the disk are younger than stars in the halo
what is the best method for measuring distances to relatively nearby galaxies - cepheid variables
what is the primary evidence that has led astronomers to conclude that the expansion of
the universe is accelerating? - observations of white dwarf supernovae
what is the universe's likely long-term fate? - The expansion will continue to accelerate.
when a star is gravitationally lensed by a foreground object, the star appears - brighter
When a star is gravitationally lensed by a foreground object, the star appears - brighter
Where did the Big Bang occur? - Everywhere in the universe at once
where is the Sun located within the Milky Way? - in the disk, about halfway from the center of the edge
which of the following is a consequence of Hubble's Law? - the more distant a galaxy is from us, the faster it moves away from us
which of the following is a false statement about the cosmic microwave background? - it
was discovered by theoretical physicists at Princeton
which of the following is an example of a standard candle. - Type- I supernovae
which of the following is not a possible scenario for the past and future development of the universe according to the available evidence? - the universe could have existed in an infinitely large state for all eternity
which of the following models best explains why our galaxy has spiral arms? - the spiral arms are a wave of star formation caused by wave of density propagating through the disk of the galaxy
which of these statements is NOT an accurate description of one of the stages in the milky way's formation? - star formation in the disk has been gradually decreasing the heavy element concentration in the interstellar medium
which type of galaxy contains the least amount of interstellar material? - ellipticals
Why are infrared and radio telescopes the instruments of choice for studying the galactic center? - dust in the plane of the milky way obscures observations at other wavelengths
why isn't the space within our solar system or the milky way expanding according to Hubble's Law? - the gravity exerted by the solar system and the milky way is strong enough to hold them together against the expansion of the universe
why should galaxy collisions have been more common in the past than they are today - galaxies were closer together in the past because the universe was smaller
why should galaxy collisions have been more common in the past than they are today? - galaxies were closer together in the past because the universe was smaller
Why should galaxy collisions have been more common in the past than they are today? - galaxies were closer together in the past because the universe was smaller
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