Chapter 19
Basic Skills/Definitions Quiz
Part A
What do we call the bright, sphere-shaped region of stars that lie within a few thousand light-years of the center of the Milky Way Galaxy?
Hint A.1
Study Section 19.1
ANSWER:

the galaxy's halo the galaxy's bulge the galaxy's disk a globular cluster
Part B
The Sun's location in the Milky Way Galaxy is ______.
Hint B.1
Study Section 19.1
ANSWER:

in the galactic disk, roughly halfway between the center and the outer edge of the disk. in the halo of the galaxy, about 28,000 light-years above the galactic disk. very near the galactic center. At the very outer edge of the galactic disk.
Part C
How do disk stars orbit the Galaxy?
Hint C.1
Study Section 19.1
ANSWER:

Disk stars orbit the Galaxy, all staying in the same thick plane-shaped region in space. Disk stars may orbit the Galaxy in opposite directions. The orbits of disk stars would eventually fill a spherical volume surrounding the center of the Galaxy. Disk stars can be found orbiting spiral arms.
Part D
What are the Magellanic Clouds?
Hint D.1
Study Section 19.2
ANSWER:

The clouds of dust and gas found interspersed in many places throughout the Milky Way Galaxy. Two small galaxies that probably orbit the Milky Way Galaxy. Two nebulae located in the disk of the Milky Way galaxy and visible only from the Southern Hemisphere. Star-forming clouds found in the constellation Orion.
Part E
Fill in the blank: Elements other than hydrogen and helium constitute about ____ of the mass of the interstellar medium.
Hint E.1
Study Section 19.2
ANSWER:

0.002 % 70 % 98% 2 %
Part F
How do we know how much mass there is in the Milky Way galaxy, inside the Sun's galactic path?
Hint F.1
Study Section 19.1
ANSWER:

By estimating the amount of gas and dust in between the stars. By measuring stellar orbits around the center of the Galaxy. By measuring the rotation speed of the spiral arms. By counting the number of stars in the Galaxy.
Part G
What do we mean by the star-gas-star cycle?
Hint G.1
Study Section 19.2
ANSWER:

It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium. It is another name for what is sometimes called the galactic fountain, in which gas rises out of the disk and then falls back down. It is the set of nuclear reactions by which heavy elements are produced in the cores of massive stars. It is the idea that stars in close binary systems can exchange gas with one another.
Part H
What are cosmic rays?
Hint H.1
Study Section 19.2
ANSWER:

They are fast moving dust particles in the interstellar medium They are subatomic particles that travel close the speed of light They are lasers used as weapons by extraterrestrials. They are another name for gamma rays and X-rays They are the highest-energy form of light.
Part I
What is a superbubble?
Hint I.1
Study Section 19.2
ANSWER:

It is a very high density region of interstellar space, filled with gas ejected from nearby star systems. It is the spherical shell of gas ejected by an unusually large supernova. It is very hot and low-density region of interstellar space, created by the combined shock waves from numerous supernovae that occurred recently within it. It is a giant cloud of gas that can form a million or more stars.
Part J
A leading model of galactic recycling holds that gas is blown high above the disk of the galaxy by supernovae and eventually cools and rains back down into the disk. This model is called _____.
Hint J.1
Study Section 19.2
ANSWER:

the cosmic ray model. the geocentric model. the galactic fountain. the star-gas-star cycle.
Part K
The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with ______.
Hint K.1
Study Section 19.2
ANSWER:

radio telescopes observing at a wavelength of 21 centimeters. space-based ultraviolet telescopes. x-ray telescopes ground-based visible-light telescopes.
Part L
Which of the following analogies best describes a spiral density wave?
Hint L.1
Read the end of Section 19.2.
ANSWER:

A spiral that winds up tighter with every galactic rotation. Traffic slowing to look at an accident in the on-coming lane. Military jets flying in formation above a football stadium. The fins of a giant pinwheel toy.
Part M
What do we mean by a protogalactic cloud ?
Hint M.1
Study Section 19.3
ANSWER:

The cloud-like halo that surrounds the disks of spiral galaxies. A cloud of gas that was once a galaxy. A term once used historically to refer to any galaxy. A cloud of hydrogen and helium that contracts to become a galaxy.
Part N
Most stars in the Milky Way's halo are ______.
Hint N.1
Study Section 19.3
ANSWER:

very young. found inside molecular clouds. blue or white in color. very old.
Part O
What is an ionization nebula?
Hint O.1
Study Section 19.2
ANSWER:

It is a colorful cloud of gas that glows because it is heated by light from nearby hot stars. It is a region of very hot, low-density gas surrounding a recent supernova. It is a clump of gas that will soon give birth to a new star. Other galaxies are sometimes called ionization nebulae.
Part P
What do halo stars do differently from disk stars?
Hint P.1
Study Section 19.1
ANSWER:

Halo stars explode as supernovae much more frequently than disk stars. They remain stationary, quite unlike disk stars that orbit the galactic center. They orbit the center of the galaxy at much lower speeds than disk star. They orbit the galactic center with many different inclinations, while disk stars all orbit in nearly the same plane.
Part Q
Which of the following statements about stars in the Milky Way appears to be generally true, based upon observations?
Hint Q.1
Study Section 19.3
ANSWER:

The older the star, the lower its abundance of heavy elements. The older the star, the faster its orbital speed. The less massive the star, the older it is. The older the star, the bluer its color. The younger the star, the higher its mass.
Part R
Which of the following correctly describes dark matter?
Hint R.1
Study Section 19.3
ANSWER:

It is another name for black holes, which emit no light. Matter that exerts a gravitational effect but does not emit any light we have been able to detect. Matter that emits only infrared light, which our eyes cannot see. It is a minor constituent of the gas in the interstellar medium.
Part S
Where does most star formation occur in the Milky Way Galaxy?
Hint S.1
Study Section 19.2
ANSWER:

It occurs around the central bulge. It occurs throughout the disk of the galaxy at a uniform rate. It occurs within the halo. It occurs in the galaxy's spiral arms.
Part T
What strange object do we think lies in the center of the Milky Way Galaxy?
Hint T.1
Study Section 19.4
ANSWER:

A gigantic X-ray binary system. A more than 2 million solar mass black hole. An enormous collection of dark matter, explaining why we detect no light at all from the galactic center. A dense cluster of young, hot stars.