PSU Astro Exam 4 – Flashcards
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What parameters do Hubble's law relate to each other
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Galaxy recession velocity and distance
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What technique for measuring distance can you use to discover Hubble's law?
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Cepheid variables in galaxies
Redshifts of bright objects in galaxies
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How do we measure speed of a galaxy relative to you?
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Doppler Shifts
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What is Hubble's law
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Faster a galaxy is moving, farther away it is
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where is the center of the universe?
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There is no center to the universe. Expansion is happening everywhere
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How many astronomers interpreted the unexpectedly fast rotation of galaxies?
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There must be a lot of dark matter whose gravity can be felt but not seen
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True or False: Dark matter and dark energy are two aspects of the same phenomenon
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False
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Why do we think there is a lot of dark matter in clusters of galaxies?
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Individual galaxies are moving so fast that they could not be held together by the gravity of visible matter
Gravitational lensing lets us measure mass even when we can't see it
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How do we know that the universe's expansion is speeding up?
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We look at objects from different times in the past to see how expansion changes with time
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How could the universe be accelerating, despite the gravitational pull of all the matter in it?
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There could be a new force or property of space that affects the universe on its largest scales
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Which feature is responsible for holding the nucleus together via gluons
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Strong
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How many types of fundamental particles exist?
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30
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How many types of quarks are there and how many types of anti quarks
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6 quarks and 6 anti quarks
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What kind of particle carries the force?
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Boson
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Considering the contents of the universe (including dark matter and dark energy) Hydrogen and Helium are....
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less than 5% of the total
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Compared to spiral galaxies elliptical galaxies have
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Less gas
Redder colors
Less new star formation
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A supernova is expected in the Milky Way
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Once in every couple hundred years, and we are overdue
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Hubble's constant is
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expansion rate of our universe at present
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The four forces are
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Gravity
Electromagnetic
Weak
Strong
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A nova is
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A star that suddenly brightens and then goes to its normal brightness again, and then the process repeats
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Why can't we see dark matter?
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It doesn't emit radiation of any sort
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What do the spiral arms in spiral galaxies contain?
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Hottest, newest stars
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Which has the events in the right order from early to late?
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Quark soup
Protons form
Nucleosynthesis
Atoms form
Star formation
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What formed in Big Bang nucleosynthesis?
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Most of the Helium-4 in the universe
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Galaxy A appears twice the angular size of Galaxy B. Assuming the 2 galaxies have the same physical size in kilo parsecs, which of the following is true?
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Galaxy B is 2 times further away then Galaxy A
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What is a quasar?
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A very luminous source due to a black hole at the center of a galaxy that is quickly growing
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The largest stars are almost the size of
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our solar system
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Why can't we see back the whole way to the Big Bang?
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Radiation scatters off matter frequently so the universe is opaque
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How many and what kind of quarks do neutrons have?
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2 down and 1 up
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What other information do we combine with the luminosity of a Type Ia supernova to measure its distance?
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Apparent brightness
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What force has its boson the photon?
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Electromagnetic
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The large magellanic cloud and small magellanic cloud are...
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Satellite dark galaxies of the Milky Way
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Which of the following is not true dark matter?
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Dark matter and dark energy are two aspects of the same phenomenon
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Which of the following main sequence turnoffs indicates the oldest globular cluster?
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G2
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What happens to the planets in a galaxy when that galaxy collides with another galaxy
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Nothing, because the spaces between stellar systems in a galaxy is much larger than their size
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True or False: Primary evidence for an accelerating universe comes from observations of young stars in the Milky Way
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False, in order to measure accelerating expansion, we need to measure the distances of objects billions of light years away
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How many times bigger are galaxies than individual stars?
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Billions/trillions of times bigger
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Which component of the Milky Way galaxy is the closest to its center?
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Bulge
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What about the spectra of Type 1 supernova?
Think: What are these different types of expansions made of?
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They should be similar but only Type II supernova have hydrogen lines
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What does our Galaxy look like?
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1. It has a large disk with spiral arms, relatively flat and thin
2. It has clouds of gas and dust in arms
3. Older yellow stars are found mostly in the central bulge
4. Old stars and globular clusters are located in a spherical halo above and below the disk
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What fraction of the energy density of the universe is disk matter?
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24%
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Why do you suppose the cat's eye Nebula has a certain symmetry?
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Bipolar jets are creating matching shapes on both sides
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How many up quarks are there in Helium-3?
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5
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What happens when two spiral galaxies collide?
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Star clusters form, initially with many young, massive blue stars in them
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How many galaxies are there in the observable universe (based on the Hubble Deep Field Academy activity that you did?
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50-100 billion
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The sun is located
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In the disk of the Milky Way, about half way out
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True or False: Stars form in molecular clouds where temperatures are about 10 degrees kelvin
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True
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The colors of the crab nebula are produced by the same elements as usual (hydrogen, oxygen, sulfur) but what about that blueish haze in the middle of the crab nebula?
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It is produced by accelerated electrons
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If a galaxy had no dark matter, we'd observe?
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The rotation velocity would decrease with increasing distance like the keplerian curve in our solar system
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True or False: A nova is more luminous than a supernova
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False
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What populations of stars are relatively old?
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Globular clusters
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True or False: At the time that the Big Bang expansion began all matter and energy in our observable universe was compressed into a single point of space
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True
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Which mysterious phenomena do scientists attribute to dark energy
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increasing rate of expansion of the universe
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How many times bigger across is the local Group of galaxies in which the Milky Way resides than the Milky Way itself?
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About 100x bigger
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Which is more luminous
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Quasar
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What causes those arcs and bubble shapes in the dust and gas distribution of the orion nebula?
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Stellar wind from local stars
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The stars in the halo of our Milky Way Galaxy are
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older and redder than those in the disk
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What is the boson for the force of gravity
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graviton
