Astro Ch. 28,29
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
By examining rich clusters of galaxies, such as the Coma Clusters, astronomers have discovered that spiral galaxies
Are found mostly in outer regions of such clusters, not in the middle
When astronomers have examined rich clusters of galaxies with their instruments, they have found that these clusters
Are more likely to contain giant elliptical galaxies than poor clusters
Where in space did the expansion of the universe begin?
Everywhere at once
What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized?
Galaxy groups are organized into huge filaments with great voids between them -- something like the structure one would see taking a cross-section of some soap bubbles
How do astronomers know that there aren't significant amounts of dark matter within our solar system?
a lot of dark matter would affect the motions (orbits) of our spacecraft as the move through the solar system, and see no such effect
If you want to check on what conditions were like in the universe a few hundred thousand years after the Big Bang, what sort of instrument would it be best to use:
a satellite with infrared and microwave telescopes on board
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
Which of the following statements about dark matter is False
astronomers have a pretty good idea what the dark matter is made of
Which of the following is not a way that astronomers can find how much dark matter there is in cluster of galaxies?
observe the radio waves coming from all dark matter; from the strength of the radio waves from each cluster, estimate the amount of dark matter needed to produce them
Why do galaxies collide, while stars almost never do?
stars are much further apart (compared to how big they are) than galaxies are
Which of the following is pretty good evidence that the universe began with a Big Bang?
the 3-degree cosmic microwave background radiation
According to the most recent data from satellites making precise measurements of the properties of the cosmic background radiation (CBR),
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)
Astronomers have measured that there is more helium in the universe than can be explained by the fusion in stars over the last 13 billion years. How do they think the extra helium got into the universe?
the extra helium was made during the first few minutes of the Big Bang, when the entire universe was hot enough for fusion to occur briefly
If a very distant galaxy looks blue overall to astronomers, from this they can conclude that:
the galaxy must have a lot of young stars and thus active star formation must still be going in it
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
Some scientists speculate that our universe is not the only universe that exists, but the only one we can gather evidence about. This idea is called
the multiverse theory
When astronomers say that the groups of galaxies are distributed isotropically, they mean that
the way galaxies are arranged in space looks the same in all directions
Which of the following can we Not learn from studying the Doppler shifts in the spectrum of galaxies beyond our Local Group?
whether they have Jupiter-mass planets around many of their stars
