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Astro Exam 3
Terms in this set (22)
How do a white dwarf's observable properties change as it ages, if it is left alone? Choose the TWO correct answers
temperature decreases, luminosity decreases
Rank the following objects in order of increasing density, from 1 (least dense) to 5 (most dense).
1) main sequence stars 2) Earth 3) white dwarf 4) neutron stars 5) black holes
which are more crowded and thus likely to collide with one another: stars within a galaxy, or entire galaxies with one another?
Entire galaxies, since neighboring galaxies are much closer together relative to their size.
How does the escape velocity from Earth change if you climb to the top of Mt. Everest?
It decreases a tiny little bit.
If a 1 solar mass black hole has Rs = 3 km, a 4 million solar mass black hole (with a mass 4 million times bigger) will have a Rs that is 4 million times bigger...
Consider that the radius of our galaxy is 50,000 light years (ly). How does the size of the black hole's event horizon (Rs) compare to the size of the galaxy?
it less than a billionth the radius of the galaxy — an utterly negligible fraction of the size of the galaxy
Compare the size of the black hole's event horizon to the typical spacing between stars in a galaxy. Neighboring stars are typically dozens of lightyears apart. Are the stars in our galaxy in danger of being swallowed up by the black hole?
What kind of stars end up as core-collapse (type II) supernovae?
high-mass main sequence star
Imagine that you take images of two main sequence stars that have the same mass. From your observations, both stars appear to be the same age. Consider the following possible interpretations that could be made from your observations. Which ones are possible? Check all that apply.
Both stars are the same age and the same distance from you // The star that is farther from you is actually the older of the two stars.
If a galaxy is 20 Mpc away from us, about how fast is it receding from us? Use 70 km/s/Mpc for the Hubble constant (H0).
Which of the following states "Hubble's Law" in words?
The farther away a galaxy is, the faster it is moving.
This question is taken from the last question in the "Expansion of the Universe" worksheet on page 91-92. It is the student debate. Student 2 makes a confusing and ambiguous statement: "each galaxy must be at the center of the universe."
Why is this statement incorrect?
because not all the galaxies are at the same place right now, so you can't say that they are all at the center
Let's reconsider Student 2's statement "each galaxy must be at the center of the universe." Is is actually possible to argue that this statement is correct. Which of the following is/are a reasonable argument that each galaxy is at the center of the universe?
if each galaxy is at the center, then there is no unique center, which is like saying that there is no center
the center of the universe is everywhere, yet nowhere
all of the space and matter in the universe was all compacted together with zero spacing in between it at the beginning
Correct! all of the above/below are reasonable
which Hubble plot belongs to the youngest universe, and why?
Figure 3, because it has the steepest slope
Assuming a constant rate of expansion, the age of the Universe equals
Why is the Andromeda galaxy moving toward us, anyway?
because it is gravitationally bound to our galaxy
When the Andromeda galaxy collides with the Milky Way galaxy, what will most likely happen to our Sun as a result?
It will not collide with any other stars.
We can measure the current expansion rate and average spacing of galaxies in the universe. Assuming that expansion rate had always been constant leads to an estimate of about 14 billion years for the age of the universe. If our measurement of the expansion rate were wrong, and the expansion had always been slower than we thought, then the actual age of the universe would be
older (but still finite).
If we could somehow remove the supermassive black hole from the center of the Milky Way galaxy, what would happen to the rest of the galaxy?
The stars would continue to orbit as normal.
How is our Sun moving in the Galaxy? What is its instantaneous direction of motion?
perpendicular / tangent to the center; sideways (90 degrees from the center)
Which of the following best describes the Big Bang?
The expansion and cooling of the universe from an originally hot and dense state.
The CMB is visible in every direction because
we are looking back to when the universe was young in every direction.
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