HW 13 - Chapter 25

An astronomer needs to measure the distance to a globular cluster of stars that is part of the Milky Way Galaxy. What method should she try to use to find the distance?

find a variable star (cepheid or RR Lyrae) in the cluster

Which of the following is Not part of the growing chain of evidence that makes many astronomers suspect there is a black hole at the very center of the Milky Way Galaxy?

the Hubble Space Telescope has shown us a visible-light image of an accretion disk at the center of the Galaxy

What have we learned from the work of Harlow Shapley and others about the 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

The scientist who made the first telescopic survey of the Milky Way and discovered that it is composed of a huge number of individual stars was

Galileo Galilei

Astronomers observe the Small Magellanic Cloud (SMC), a not very dense, rather small galaxy near us. They notice that even those stars that formed recently have relatively few heavier elements (when compared to such

because the SMC is small and its stars are widely spaced, the rate of star formation (and star death) is much slower there

Which of the following statements about dark matter in the Galaxy is False?

While the dark matter cannot be observed with our present-day instruments, we still have a pretty good idea what it consist of

The very strong source of radio waves at the center of our Galaxy is called

Sagittarius A

Astronomers making observations in our Galaxy have been able to rule out a number of suggestions for what the dark matter in the Galaxy might be. Which of the following have we Not been able to rule out (which suggestion is still "in the running")?

a new kind of subatomic particle

The central region of our Galaxy is not as flat as its main disk of stars. Which of the following has roughly the same shape as our central region of stars?

a peanut

Astronomers now know that surrounding the main body of our Galaxy (which our various kinds of telescopes have shown to us) and our fainter halo of stars there is

an invisible halo made of what astronomers are calling "dark matter"

If I want to find a sizeable collection of Population II stars in the Milky Way Galaxy, where would be a good place to look?

in a globular cluster high above the Galaxy's disk

Our Milky Way Galaxy is what type of galaxy?

spiral

In the future, astronomers believe that the Milky Way Galaxy has additional collisions in store. Which of the following nearby galaxies are eventually going to collide with our own?

the Large Magellanic Cloud

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

William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. Today we know this is not the case. What was a key reason that Herschel did not realize our true position in the Milky Way?

the dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the Milky Way that surrounds us

Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies?

the observation of long moving streams of stars that continue to orbit through our Galaxy's halo

What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical?

the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth

A "galactic year" as defined by astronomers is:

the time it takes the Sun to revolve once around the center of the Milky Way Galaxy

Recently, astronomers have observed 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 an observation 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

How do astronomers measure the mass that the Galaxy contains inside the orbit of the Sun?

they measure the distance to the center of the Galaxy and the period of the Sun's orbit and then use Kepler's Third Law