Unit Test 2
(According to our textbook) roughly what percent of the mass and energy contents of the universe is made up of dark matter?
95%
if you wanted to write the complete cosmic address for yourself, including every location or the structure you live in, which of the following would be that address?
Earth, the Solar System, the Milky Way Galaxy, the Local Group, the Virgo Supercluster
The very strong source of radio waves at the center of our galaxy is called
Milky Way CC1
Astronomers today know a lot about the size and shape of the Milky Way Galaxy. Which of the following common objects most resemble the shape of our galaxy.
a CD or DVD
According to the general theory relativity, light and other radiation coming from a white dwarf or neutron star should (and experiments show that it does) exhibit
a gravitational redshift
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 (orbit) or our spacecraft as the move through the solar system, and see no such effect
The center of a black hole is called
a singularity
From which of the following will a wave of light show the greatest gravitational redshift:
a white dwarf
which of the following did NOT happen during the first few minutes after the Big Bang a) some very massive early stars were formed b)energy was converted into matter c) two or three of the simplest elements fused together d) matter and antimatter collided and turned into energy c) temperatures throughout the universe were hotter than the cores of stars today
a) some very massive early stars were formed
factoring everything we currently know about the universe, our assumed age of the universe is
about 13.8 billion years
the reciprocal of the Hubble constant (1/4H) is a rough measure of the:
age of the universe
In our modern view of the expansion of the universe, we understand that it is SPACE that is stretching; individual galaxies don't speed away from each other as if they were rocks. In that case, why do galaxies show a red-shift?
as space stretches, the waves of radiation in space also strech and their wavelengths increase
Which of the following is NOT true about the Local Group of galaxies (of which the Milky Way is a member) a) it is a member of the same supercluster as the Virgo cluster b) it has about a thousand member galaxies c) it has more elliptical galaxy members than spiral galaxies d) the Milky Way is one of its more massive members e) it has few galaxies when compared to a rich cluster
b) it has about a thousand member galaxies
Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally
bluer and smaller
How did Edwin Hubble establish that there are other galaxies , quite removed from the Milky Way Galaxy?
by observing a Cepheid variable in the nearby galaxy and using it to get the distance.
When Einstein proposed his General Theory of Relativity, he suggested some pretty strange ideas about space, time, and gravity. How did scientist in 1919 show that Einsteins theory described the behavior of the real world and wasn't just as a crazy hypothesis?
by observing starlight coming close to the Sun during an eclipse
Which of the following objects (small or large) have not been ruled out as a potential source of dark matter in the Galaxy? a) hydrogen gas that is at low temperatures compared to stars b) Jupiter mass planets or brown-dwarf planets c) a new kind of subatomic particle d) large quantities of dust (like we find in nebulae) e) black holes
c) a new kind of subatomic particle
Which type of galaxy is observed to contain mostly older stars
elliptical
where in space did the expansion of the universe begin?
everywhere all at once
Edwin Hubble was able to show that (with the exception of our nearest neighbors) the farther the galaxy is from us, the
faster it is moving away from us
When quasars "shine" (in visible light and other kinds of radiation) with a lot of energy, where (what location) does this huge amount of energy come from?
from an accretion disk around a supermassive black hole
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.
What objects did Harlow Shapley use as "signposts" to figure out the extent of Milky Way Galaxy and the location of its center.
globular clusters
Where would you look for the youngest stars in the Milky Way galaxy?
in the disk
According to the general theory of relativity, the presence of mass
is equivalent to the presence of light
According to Cosmological Principle, the universe:
is isotropic and homogeneous
The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and
its rotational velocity
If quasars are at the distance most astronomers think they are, then (for most luminous ones) their luminosity must be:
like the combined luminosity of a hundred trillion (1014) suns
To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?
mass
Today, astronomers find compelling evidence that the energy source of the quasars and active galaxies is
matter falling toward a supermassive black hole at the center of the galaxy
Why is the use of Hubble's Law to measure distances so important to astronomers.
most galaxies are so far away, the only way to get distances to them is to use Hubble's Law.
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 than Galaxy A, the Galaxy B will
move away from us three times faster than A
How do astronomers now explain the fact that the energy emitting regions for quasars are so small?
quasars are the result of matter falling into a black hole; the event horizons of even supermassive black holes are extremely small on the cosmic scale
Today we know that all quasars have in common is that they appear to be small sources of energy with
redshifts that indicates they are far away
Which of the following observations is a convincing argument for the idea that quasars are located inside galaxies? a) you can't fool me; there is no evidence whatsoever b) relatively nearby quasars show "fuzz" around them with the same spectra and redshift as the quasars c) quasars vary with brightness over time d) quasars have been discovered in more time than one direction in space
relatively nearby quasars show "fuzz" around them with the same spectra and redshift as the quasars
Far from a black hole (at the distance of another star), which of the following is a possible way to detect it.
search for flickering x-rays being given off from an accretion disk around the black hole, as it "eats" part of a neighbor star
Our galaxy is what type of galaxy?
spiral
When astronauts aboard the International Space Station in space let go of an orange, it just floats there. Why is that?
the ISS is falling around Earth, in free fall, things feel no weight
In which of the following domains of the universe have astronomers NOT found evidence for the presence of dark matter today?
the Solar System
The Hubble Space Telescope has enabled astronomers to explore an active galaxy such as M87 in remarkable detail. Which of the following observations of M87 is NOT an important part of the web of evidence that shows it must have a supermassive black hole at the center.
the discovery of a gravitational lens in M87
what observations in astronomy, made AFTER the discovery of quasars, was a big help to astronomers in figuring out what quasars really were
the discovery that the Milky Way Galaxy has a black hole at the center with enough mass for 4 million Suns
the model of the universe that involves an enormous increase in scale in a very short time is called
the inflationary universe model
How do astronomers explain the energetic jets that come out of quasars and active galactic nuclei in opposite directions
the jets are "spit out" from the chaotic accretion disk of supermassive black holes in directions that are perpendicular to the disk
Once a black hole forms, the size of its event horizon is determined only by
the mass inside the event horizon
Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?
the observations of long moving streams of stars that continue to orbit through our Galaxy's halo
According to our modern theories, the geometry of the entire universe(all of space-time) may be curved or warped. This is a pretty bizarre notion; what other discovery in astronomy has made us believe that space be able to curve or warp?
the properties of black holes
The first time that astronomers observed both gravitational waves and electromagnetic waves from the same event, what they were observing was:
the spiraling toward each other of two neutron stars
the first time that astronomers observed both gravitational waves and electromagnetic waves from the same event, what they were observing was:
the spiraling toward each other of two neutron stars
What is the strongest known force in the universe?
the strong nuclear force
When astronomers say that the groups of galaxies are distributed isotropically they meant that
the way galaxies are arranged in space looks the same in all directions
Edwin Hubble developed a classification scheme for galaxies. By what characteristic did he classify galaxies?
their shape
Recently, astronomers have studied stars and other objects that orbit the center of the Milky Way Galaxy farther out than our sun, but move around faster than we do. How do astronomers think such observations can be explained?
there must be a great deal of invisible dark matter outside the orbit of the Sun whose gravitational pull explains the faster motions we see out there
Astronomers have established that quasars and active galaxies have a lot of mass in their centers in a very small volume of space. Why can't this mass be in the form of a cluster of stars that are quite closer to each other?
to fit as much matter into the cluster as we observe, the stars in the cluster must be so close to each other they would merge into a superstar and soon collapse into a black hole
Which of the following objects is considered useful to astronomers as a standard bulb" for determining distances?
type la supernovae
After several decades of observation, astronomers have concluded that quasars are
very powerful and compact sources of energy at the centers of distant galaxies
Where is the approximate location of the Sun in the Milky Way galaxy?
we are in the disk of the Galaxy, about 3/5 of the way from the center
