According to Hubble's Law, if two galaxies are not part of our Local Group, and galaxy B is three times farther away from us as Galaxy A, then Galaxy B will - ️️ove away from us three times faster than A
According to our current understanding, giant elliptical galaxies form: - ️️by the mer...
ASTR 121|85 Quiz Questions Perfectly
Answered|2024
According to Hubble's Law, if two galaxies are not part of our Local Group, and galaxy B is three times
farther away from us as Galaxy A, then Galaxy B will - ✔ ✔ ove away from us three times faster than
A
According to our current understanding, giant elliptical galaxies form: - ✔ ✔ by the merger (or
swallowing) of a number of smaller galaxies in a cluster of galaxies
According to the models of the universe we discussed in this course, why do the galaxies move apart
(why do we have Hubble's law)? - ✔ ✔ as a result of the Big Bang, space itself is stretching, and this
stretching carries the galaxies away from each other
According to the most recent data from satellites making precise measurements of the properties of the
cosmic microwave background, - ✔ ✔ the dark energy makes up just a little less than 70% of the
density of the universe, making it the most significant constituent of the mass-energy
After the Big Bang, in order for the universe to become transparent to light and other electro-magnetic
radiation, what had to happen? - ✔ ✔ the density of the universe had to decrease (to 1000 nuclei
per cubic centimeter or less)
Among irregular galaxies, what makes the Large and Small Magellanic Cloud especially useful for
astronomers? - ✔ ✔ they are (for galaxies) very close to us, so they are easy to study
An astronomer discovers a massive galaxy which has four nuclei. What is a likely explanation for a galaxy
having more than one nucleus? - ✔ ✔ the galaxy must have swallowed several smaller galaxies that
were its neighbors
An astronomer is observing a distant galaxy which looks blue. Which of the following can she conclude
from this observation? - ✔ ✔ the galaxy must have a lot of star formation going on at the time we
are seeing it
Astronomers believe that the center of our Galaxy has a black hole with enough mass inside to make
almost 4 million Suns! How do astronomers think a black hole could acquire so much mass? - ✔ ✔
the center of our Galaxy is a much more crowded region than where the Sun is found; we still see
material falling toward the center and material has fallen in for billions of years
Astronomers believe that the large elliptical galaxies formed - ✔ ✔ from the collision and merger of
many smaller fragments
, Astronomers can now report that active star formation was going on at a time when the universe was
only 20% as old as it is today. When astronomers make such a statement, how can they know what was
happening inside galaxies way back then? - ✔ ✔ they examine the spectra of galaxies (or the overall
colors of galaxies) with the highest redshifts they can find
Astronomers now know that surrounding the main body of our Galaxy and our fainter halo of stars there
is - ✔ ✔ an invisible halo made of what astronomers are calling "dark matter"
Astronomers now think that there is a black hole with more than 4 million times the mass of our Sun at
the center of our Galaxy? Roughly how large would the event horizon of such a supermassive black hole
be? - ✔ ✔ about 35 times the size of the Sun (0.3 AU)
Astronomers today know a lot about the size and shape of the Milky Way Galaxy. Which of the following
common objects most resembles the shape of our Galaxy? - ✔ ✔ a CD or DVD
At first, right after the Big Bang, the universe was too hot for nuclei and electrons to combine into the
kinds of neutral atoms that are familiar to us today. How soon after the beginning did it become cool
enough for neutral atoms to form? (i.e. nucleons with electrons, not just the nucleons) - ✔ ✔ a few
hundred thousand years
Based on many surveys of the average density of matter in the universe (regular matter and dark
matter), astronomers now conclude that the average density of the universe is:
(To answer this, think about the role an increase in density (and thus gravity) has on the expansion of
the universe) - ✔ ✔ essentially equal to zero (density is super low)
Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of
that galaxy? - ✔ ✔ you must take a spectrum of the galaxy and measure the red shift
By examining rich clusters of galaxies, such as the Coma Clusters, astronomers have discovered that
spiral galaxies - ✔ ✔ are found mostly in the outer regions of such clusters, not in the middle
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify
galaxies? - ✔ ✔ their shape
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther a galaxy is
from us, the - ✔ ✔ the faster it is moving away from us
Factoring in everything we currently know about the history of the universe, our best estimate for the
age of the universe is - ✔ ✔ about 13.8 billion years
For the next 5 questions, consider the following five kinds of objects: open cluster, giant molecular
cloud, globular cluster, group of O and B stars, and planetary nebulae. - ✔ ✔ open cluster
giant molecular cloud
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