Chptr 25 The Milky Way Galaxy - Starry Night

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 recent stars in our Milky Way.) What is the likely explanation for this deficiency?

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

Where would you look for the youngest stars in the Milky Way Galaxy?

in the disk

What was especially noteworthy about the Sagittarius Dwarf Galaxy when it was discovered among the small galaxies near the Milky Way?

it was on a collision course with the Milky Way and would be swallowed by it eventually

Which statement best describes the position of the Sun and Solar System within the Milky Way?

The Sun and Solar System are located about two thirds of the way from the center to the edge of the galaxy

Which statement best describes the geometry of the solar system's location within the Milky Way galaxy?

The angle between the plane of the solar system and the galactic plane is large but less than a right angle.

Carefully examine the shape of the spiral arms. In which direction do you think the galaxy is rotating?

The galaxy is rotating in a clockwise direction

Objects orbiting around the center of the Milky Way obey Kepler's 3rd Law. This means that:

a cloud of gas or star that is further from the center will generally take more time to orbit

You suddenly get an uncontrollable urge to find out more about the other side of the Milky Way Galaxy (the regions beyond the center). Where should you rush off to?

a radio telescope that can observe at 21-cm wavelengths

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 17 times the size of the Sun

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

The Sun moves with a velocity of about 220km/sec in its orbit about the galactic center. What is the approximate time required for the Sun (and the entire Solar System) to complete one orbit of the galactic center?

230 million years

What is the general shape of the Milky Way galaxy?

A flattened disk in a spiral shape with a bulge in the center

The Milky Way appears to us as a patchy and irregular band across the sky. What accounts for this?

Irregular clouds of interstellar dust block out the central regions of the galaxy from our view

Your weird cousin, who is really into astronomy, decides that the return address he uses on his letters is incomplete! To his city, state, and country, he begins to add: "North America, Earth, Solar System..." If he now wants to include the name of the Galaxy's spiral-structure feature in which the Earth is located, how should his address end?

Orion Spur

The current Sky Chart view shows a gamma ray view of our galaxy. Locate our galaxy's "hot spot" in order to determine the location of the supermassive black hole at the center of the Milky Way. In which constellation is the galactic core of the Milky Way located?

Sagittarius

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

Sagittarius A

The Solar System is embedded within the galaxy. Why does the Milky Way appear as a narrow band of light instead of appearing as faint but evenly distributed light across the entire sky?

The galaxy is flattened and we view it edge-on from its interior

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

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

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?

all of the above

The Population I stars in the Milky Way Galaxy

all of the above

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

Radio astronomy has played a pivotal role in showing us the detailed structure of the Milky Way Galaxy. Which of the following techniques would a radio astronomer use as an essential part of an investigation of this structure?

measuring the Doppler shift of a line in a radio spectrum

Our Milky Way Galaxy is what type of galaxy?

spiral

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

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

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: a. the time it takes the Earth to go around the Sun (starting with when it's closest in its orbit to the center of the Galaxy)

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