Question 1

Cepheids and RR-Lyrea stars are characterized by each of the following EXCEPT ONE.Which is the exception?

Accepted Answer

A)  giants 
B)  unstable 
C)  supernova remnants 
D)  variable

Question 2

Which stars undergo a helium flash in their cores?

Accepted Answer

A)  stars of less than 2 solar masses 
B)  stars that contain helium 
C)  stars of more than 2 solar masses 
D)  stars that have become red giants

Question 3

What is the relationship between a giant molecular cloud and an H II region?

Accepted Answer

A)  They are two names for the same entity. 
B)  In giant molecular clouds, H II regions surround ultraviolet-emitting stars (types O and 
B) , which have ionized the hydrogen around them. 
C)  In H II regions, giant molecular clouds are concentrations of other molecules like CO and H₂O. 
D)  Giant molecular clouds evolve into H II regions as the molecules other than hydrogen are used up in star formation.

Question 4

Degeneracy occurs when:

Accepted Answer

A)  electrons inside a star resist being pushed closer together than a certain limit. 
B)  solar wind particles become trapped in Earth's magnetic field. 
C)  magnetic fields inhibit the motion of charged particles in sunspots. 
D)  thermonuclear reactions halt the contraction of a protostar.

Question 5

In about five billion years,the core of our Sun will be composed of:

Accepted Answer

A)  hydrogen. 
B)  helium. 
C)  carbon. 
D)  silicon.

Question 6

If you make a list of the 100 nearest stars in the sky,you will find that most of them are:

Accepted Answer

A)  white dwarfs. 
B)  main-sequence stars. 
C)  giants and supergiants. 
D)  brown dwarfs.

Question 7

When a star consumes all of the energy it can from hydrogen fusion in its core, the next long-term energy-producing phase is:

Accepted Answer

A)  helium fusion in the core. 
B)  helium fusion in a shell around the core 
C)  hydrogen-fusion in a shell around the core. 
D)  gravitational energy released in a Kelvin-Helmholtz condensation.

Question 8

To detect MOST interstellar material requires:

Accepted Answer

A)  optical telescopes. 
B)  gamma ray observatories. 
C)  radio telescopes. 
D)  ultraviolet detectors.

Question 9

What is a protostar?

Accepted Answer

A)  a sphere of gas after collapse from an interstellar cloud but before nuclear reactions have begun 
B)  a small interstellar cloud before it collapses to become a star 
C)  a star near the end of its life before it explodes as a supernova 
D)  a shell of gas left behind from the explosion of a star as a supernova

Question 10

What happens to the luminosity of a low-mass star as it passes through a helium flash?

Accepted Answer

A)  The luminosity, which was increasing slowly before the helium flash, suddenly brightens by several orders of magnitude. 
B)  The luminosity, which was decreasing slowly before the helium flash, suddenly brightens by several orders of magnitude. 
C)  The helium flash affects only the core. The luminosity of the star remains unchanged for a long time after the flash. 
D)  The luminosity, which was rising before the helium flash, drops quickly after the helium flash.

Question 11

What is the relationship between the mass of a protostar and the time needed for it to reach the main sequence after it forms inside an interstellar cloud?

Accepted Answer

A)  More massive protostars reach the main sequence in a shorter time than less massive protostars. 
B)  Less massive protostars reach the main sequence in a shorter time than more massive protostars. 
C)  The time needed is independent of the mass of the protostar. 
D)  The time needed is least for a protostar of approximately 4 solar masses and longer for protostars of either greater or lesser mass.

Question 12

The density of carbon monoxide is observed in a particular interstellar cloud to be 500 CO molecules per cubic meter.What will be the expected density of molecular hydrogen gas,H₂,in this cloud?

Accepted Answer

A)  500 million molecules of H₂ per cubic meter 
B)  500 molecules of H₂ per cubic meter 
C)  5 million molecules of H₂ per cubic meter 
D)  50,000 molecules of H₂ per cubic meter

Question 13

How long does core helium burning last in a star compared with core hydrogen burning?

Accepted Answer

A)  about 1/2 of the time spent burning hydrogen 
B)  about 1/10 of the time spent burning hydrogen 
C)  about 1/100 of the time spent burning hydrogen 
D)  about three times as long as the time spent burning hydrogen

Question 14

A reflection nebula is made visible by:

Accepted Answer

A)  thermal energy emitted as a continuous spectrum by the very hot gas, much like that emitted by a hot body on Earth. 
B)  light from embedded stars reflected over a wide range of wavelengths toward Earth by crystals of water, methane, and ammonia ices. 
C)  emission lines from hydrogen, which itself has been ionized by UV light from embedded stars. 
D)  blue light preferentially scattered by dust grains.

Question 15

The Pauli exclusion principle states that two identical electrons (or other particles)cannot have the same:

Accepted Answer

A)  electrical charge at the same time. 
B)  speed at the same time. 
C)  position at the same time. 
D)  speed and direction at the same time.

Question 16

From the time a star of more than 1 solar mass reaches the ZAMS until it leaves the main sequence,the star's evolution on the main sequence is:

Accepted Answer

A)  upward and to the left, along the main sequence. 
B)  down and to the left, toward the white dwarves. 
C)  upward and to the right, but only very slightly. 
D)  straight upward as its luminosity increases.

Question 17

At what point in its evolution does a protostar stop shrinking and stabilize into a star?

Accepted Answer

A)  when nuclear processes generate enough energy and internal pressure to resist gravitational contraction 
B)  when gravitational contraction has heated up the gas to the point where radiation pressure opposes gravity for the first time 
C)  when the protostar has spun off enough of its matter and is spinning fast enough that centrifugal force opposes the gravitational contraction 
D)  when nuclear reactions end in the star's core

Question 18

What is an emission nebula (H II region)? See Figure 11-3 in Comins,Discovering the Essential Universe,6th ed.

Accepted Answer

A)  a region of ionized hydrogen around one or more hot O- and B-type stars 
B)  a region of molecular hydrogen inside a giant molecular cloud 
C)  a region of neutral, atomic hydrogen in interstellar space 
D)  a region of gas and dust formed by the explosion of a massive star

Question 19

The stars of a cluster are plotted on an H-R diagram.It is seen that the main sequence is well populated all along its length and that there are many stars above (and to the left of)the main sequence at its lower end.What can you say about the age of this cluster?

Accepted Answer

A)  This cluster is very young. 
B)  This cluster is very old. 
C)  These characteristics could represent either a very young or a very old cluster. 
D)  This description is not sufficient to make any conclusions about the age of the cluster.

Question 20

Dark nebulae are extreme examples of:

Accepted Answer

A)  interstellar extinction. 
B)  interstellar reddening. 
C)  emission nebulae. 
D)  a reflection nebula.

Exam 11: The Lives of the Stars From Birth Through Middle Age