study exam 3 ast

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Valencia College *

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Course

1002

Subject

Astronomy

Date

Apr 3, 2024

Type

docx

Pages

3

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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.
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