Question 1

The Messier Catalog is

Accepted Answer

A)   a listing of all the stars within the Local Bubble
B)   a list of all the HII regions visible without a telescope
C)   a list of nebulae, star clusters, and galaxies that might be mistaken for a comet far from the Sun
D)   a list of regions where dark clouds with large numbers of molecules can be found
E)   the catalog that some graduate students accidentally dropped in the mud C

Question 2

How do fragile structures like acetaldehyde (CH3CHO) molecules survive in the harsh environment of interstellar space? Why are they not destroyed by high-energy radiation from stars?

Accepted Answer

A)   such molecules are only found in the shadows of the stars
B)   such molecules are found only on planets or comets, not in space
C)   such molecules are protected by the presence of hot interstellar hydrogen
D)   such molecules are found only in dense clouds that have a lot of dust; the dust keeps the radiation from hot stars from reaching the molecules
E)   such molecules are found only where very cool stars are present, that's why they are so very rare in the GalaxySection 20.3: Interstellar Dust D

Question 3

An astronomer wants to observe a cloud of dust in a relatively close part of the Galaxy. Unfortunately, this dust cloud is not located in the direction of a crowded region of stars. What instrument would be the most help in finding this cloud.

Accepted Answer

A)   a visible-light telescope (like the Keck)  with a camera or CCD detector
B)   an x-ray telescope in orbit around the Earth
C)   a giant vat of cleaning fluid deep in a mine-shaft
D)   a sensitive infra-red telescope in orbit around the Earth
E)   a spectroscope that can search for the line radiation from highly ionized atoms D

Question 4

Astronomers now understand that the dark regions or rifts visible in parts of our Galaxy that are otherwise crowded with stars are caused by:

Accepted Answer

A)   the absence of stars in regions that have been cleared out by recent explosions
B)   starlight being blocked by otherwise invisible planets at the outskirts of our solar system
C)   clouds with a considerable amount of dust which blocks the light of the stars behind them
D)   huge groups of stars that only give off radiation in the infrared and not in visible light
E)   holes in the structure of our Galaxy

Question 5

The dust in the dust clouds in interstellar space consists of

Accepted Answer

A)   atomic gas
B)   molecular gas
C)   tiny solid grains
D)   pieces of ice ranging from several meters to a kilometer in diameter
E)   none of the above

Question 6

Which of the following descriptions of interstellar dust is FALSE?

Accepted Answer

A)   interstellar dust has a (tiny)  rocky core surrounded by an ice mantle
B)   interstellar dust must be roughly the size of the wavelength of visible light
C)   interstellar dust must be made of some of the most common elements in the universe
D)   interstellar dust must be at a temperature equal to the outer layers of a star
E)   interstellar dust particles can sometimes be found in meteorites and can be identifiedSection 20.4: Cosmic Rays

Question 7

A friend of yours who has not taken an astronomy class looks at your textbook and really likes the picture of the Pleiades, a cluster of stars surrounded by a bluish reflection nebula. She wants to know what causes that beautiful blue glow. To explain it to her, you want to compare the process that causes the blue glow to something that is in your friend's everyday experience. Which of the following terrestrial phenomena is the result of the same type of process that makes a reflection nebula in space?

Accepted Answer

A)   the blueish glow of the flame on a gas stove
B)   the blue light you see reflected from a blue sweater
C)   the blue color of the Earth's sky
D)   the blue-white color of the hottest stars
E)   the blue feeling you get when you don't do well on an astronomy exam

Question 8

The red color we see on a lot of photographs of nebulae comes from which element?

Accepted Answer

A)   helium
B)   oxygen
C)   carbon
D)   hydrogen
E)   not an element at all, but the molecule carbon dioxide

Question 9

You are an astronomer whose supervisor has just forbidden drinking alcoholic beverages near the observatory. In frustration, you under?take a search for alcohol molecules in space. Where would your search be most likely to succeed?

Accepted Answer

A)   in an interstellar cloud of gas and dust
B)   in a binary star system
C)   in the surface layers of our Sun, which is the nearest star
D)   in a region of ionized hydrogen near an O type star
E)   you can't fool me; no one has observed alcohol in space

Question 10

The Local Bubble is

Accepted Answer

A)   a region of low density interstellar gas extending several hundred LY around the Sun
B)   a region around any exploding star where material is expanding from the explosion
C)   another name for the Milky Way Galaxy
D)   the region around very hot stars where hydrogen is ionized
E)   a night club specializing in champagne located in Bayonne, New Jersey

Question 11

Which of the following statements about interstellar matter is FALSE?

Accepted Answer

A)   99% of it is in the form of gas
B)   it is clumpy: much of it is distributed in patchy, irregular clouds
C)   the total mass in interstellar matter in our Galaxy is about 5% of the mass in stars
D)   if the matter were spread out evenly, it would be about as dense as the Earth's atmosphere
E)   it also includes grains of dust

Question 12

Some of the interstellar gas in our Galaxy has been heated to millions of degrees, a temperature that surprised astronomers when it was first discovered. How do we now think that gas between stars gets that hot?

Accepted Answer

A)   any gas close to a star will naturally get that hot
B)   very powerful shock waves from exploding stars heat the gas they come into contact with
C)   gas gets to be this hot when hydrogen atoms flip their spin and give off 21-cm radiation
D)   such gas is heated by the radiation given off by complex molecules in clouds
E)   astronomers have no idea how gas gets this hot; this is an unsolved mystery in astronomy

Question 13

The term "baryon cycle," as astronomers use it, refers to:

Accepted Answer

A)   the steps in the fusion of hydrogen into helium at the center of stars
B)   the kinds of orbits short-period comets take around the Sun
C)   the movement of interstellar material into the Galaxy and into stars and then the movement out when stars end their lives
D)   the change of individual atoms into molecules in dusty interstellar clouds
E)   exercise equipment they had in the White House for President Obama

Question 14

Why can astronomers not tell from what direction a particular cosmic ray started toward the Earth?

Accepted Answer

A)   all cosmic rays are scattered by dust in interstellar space
B)   we don't believe cosmic rays have a particular source; they have always been circulating around the Galaxy
C)   cosmic rays are reflected by interstellar matter and thus are always reversing direction
D)   cosmic rays are charged particles and are thus spiral around the Earth and the Galaxy's magnetic field
E)   cosmic rays are very strongly Doppler shifted

Question 15

If an astronomer wanted to find some relatively complex molecules in space, what technique should she use?

Accepted Answer

A)   point a gamma-ray telescope toward the center of the Milky Way Galaxy
B)   take a spectrum of the visible light coming from our own Sun
C)   point a radio telescope into regions in the galaxy where there is a lot of dust
D)   use an ultra-violet telescope above the Earth's atmosphere to find highly ionized atoms
E)   use the Hubble Space Telescope to take many visible-light images of faint nebulae

Question 16

Cosmic rays are

Accepted Answer

A)   high-energy electro-magnetic radiation
B)   fast-moving dust grains
C)   neutrinos of various types
D)   highly reddened light emerging from dust clouds
E)   high-speed atomic nuclei, electrons, and positrons

Question 17

Which of the following is not a place where astronomers believe interstellar dust grains can form?

Accepted Answer

A)   in the cooling winds of material ejected from red giant stars
B)   in the material flowing out of exploded stars, after it has cooled
C)   in denser clouds of interstellar matter
D)   in HII regions
E)   all of the above are places where dust grains regularly formSection 20.6: Interstellar Matter around the Sun

Question 18

Given the presence of dust throughout the disk of the Milky Way Galaxy, what is the best technique for learning about more distant regions of our galaxy's disk.

Accepted Answer

A)   look for blue radiation from stars and nebulae, since the light is reddened
B)   look for red light from stars and nebulae
C)   look for radiation at long wavelengths, for example in the infrared region of the spectrum
D)   look for HII regions, whose high-energy radiation penetrates dust
E)   send a spacecraft to Pluto, from where we can see above the Galaxy's disk

Question 19

What happens in the process of fluorescence?

Accepted Answer

A)   water molecules are broken up into hydrogen and oxygen
B)   atoms absorb ultraviolet rays and convert them to visible light as their electrons cascade to lower energy levels
C)   hydrogen is transformed into helium where gas is very, very hot
D)   radio waves are given off as molecules change their vibration or rotation
E)   fluorine gas is released by chemical reactions in the outer layer of a star

Question 20

The largest types of clouds found in interstellar space are

Accepted Answer

A)   HI regions -- clouds of neutral hydrogen
B)   molecular clouds with supplies of dust and molecules
C)   HII regions -- clouds of ionized hydrogen
D)   interstellar grains
E)   all these clouds are approximately the same size

Exam 20: Between the Stars