Homework 11

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Started: Nov 16 at 9:38am Quiz Instructions

Question 1 1 pts

One of the factors that misled the Herschels into concluding that we are at the Universe's center was

hot hydrogen gas in our 's disk, its emission hiding the more distant

dust that obscures the more distant stars and thereby localizes observations

gravitational lensing of light by dark matter, distorting the positions of the stars

some “neutron clusters" are actually distant that are distributed uniformly around the

Question 2 1 pts

Galaxies are like very big, very distant star clusters. Galaxy P is composed of easily visible, bright blue stars with many dimmer red stars but no bright, red stars. Galaxy Q is composed of easily visible bright, red stars with many dimmer red stars and some dimmer blue/white dwarfs but no bright, blue stars. Which galaxy is older (i.e. which galaxy's stars formed longer in the past)? Galaxy P is older

Galaxy P and Galaxy Q are about the same age

Galaxy Q is older

It is impossible to know which galaxy has existed longer from the information provided

Question 3 1 pts

What appears to happen to a clock as it approaches and reaches the event horizon around a black hole, when viewed by a remote observer?

Time appears to pass at a much faster rate, becoming infinitely fast at the event horizon

Time appears to slow down and completely stop

Time speeds up because of the strong gravitational field but does not pass infinitely fast

Time passes uniformly since nothing changes the progress of time

Question 4 1 pts

If most of the mass of a particular galaxy was located in a big ball near the very center of the galaxy, then in the outer part of this galaxy we would expect the orbital speeds of stars to decrease with increasing distance from the center. This behavior would be described by Newton's Third Law

Wien's Law

Hubble's Law

Kepler's Third Law

Question 5 1 pts

From our Galaxy's rotation curve, astronomers know that there is a large amount of dark matter distributed evenly around our Galaxy's halo. The matter is "dark" because it emits no obvious, bright light. Our Galaxy formed from a collapsing ball of gas, and stars started to form first at the outskirts of our Galaxy's halo. Given the information in this question, which of these objects is NOT a good candidate for the dark matter?

Black Holes

White Dwarfs

Red Dwarfs

A-type stars

Question 6 1 pts Suppose it were possible to lower a yellow light toward the event horizon of a black hole. What would you see while watching from a safe distance?

The color of the light would change to green and then to blue

The light would remain yellow, but would appear brighter and brighter

The color of the light would change to orange and then to red

The brightness and color of the light would each remain unchanged

Question 7 1 pts

Where would you look for a supermassive black hole?

at the center of a galaxy

at the center of our Universe

orbiting a normal star in our Galaxy

at the center of a

Question 8 1 pts

Orbiting GPS satellites can precisely map locations on the Earth from the time it takes a signal to travel between the satellites and the location. Depending on the position of the satellites in the Earth's gravitational field, travel times have to be corrected by about 0.01 seconds per year. If this correction was not made, GPS directions would lead to the wrong locations on the Earth. That this correction needs to be made tests which law or theory? Wien's Law

Einstein's Theory of General Relativity

Kepler's Third Law

Newton's Theory of

Question 9 1 pts

Cepheid variable stars are useful to astronomers as indicators of

stars with very high-speed motion

sizes, particularly of white dwarfs

the existence of black holes

distances, particularly to galaxies

Question 10 1 pts

Stars in star clusters are born and arrive on the at roughly the same time. An astronomer observes a and notices no bright blue Main Sequence stars in the cluster. In fact, the last Main Sequence star visible in the cluster is a green star of spectral type F that has a surface temperature of about 7000K. All other stars have turned off towards the area of the H-R diagram. How long has the star cluster existed?

About 3 billion years

About 10 billion years

About 30 billion years

About 100 billion years