Astronomy Exam 4 MTSU

Question and answer review

Use the attached H-R diagram. Where are the dimmest stars?

A. Y
B. V
C. W
D. T

B. V

Use the attached H-R diagram. The location of the most massive main sequence stars is

A. T
B. Z
C. W
D. V

C. W

Use the attached H-R diagram. The location of the hottest stars is

A. W
B. Z
C. T
D. V

A. W

Use the attached H-R diagram. The location of the largest-size stars is

A. V
B. T
C. Z
D. W

B. T

Use the attached H-R diagram. The location of the giant stars on this diagram is

A. U
B. W
C. S
D. X

C. S

What are the two physical parameters of stars which are plotted in the H-R diagram?

A. Luminosity and mass
B. Radius and mass
C. Mass and temperature
D. Luminosity and temperature

D. Luminosity and temperature

Which star will spend the longest time on the main sequence?

A. 0.5 Msun
B. 1.0 Msun
C 2.0 Msun
D. 4.0 Msun
E. 8.0 Msun

A. 0.5Msun

What is one characteristic of a pulsar?

A. Low temperature
B. Large magnetic field
C. Large size
D. Gravity so strong that light cannot escape

B. Large magnetic field

A neutron star is about the same size as

A. the sun
B. a US city
C. the Earth
D. the Moon

B. a US city

What are the large interstellar gas and dust clouds shown on Slide 1?

A. old stars dying
B. red giant stars
C. groups of white dwarf stars
D. new star formation

D. new star formation

Sirius is about 2 times the temperature as the Sun and 2 times the size. The luminosity of Sirius compared to the sun is

A. 4 times larger than Lsun
B. 32 times larger than Lsun
C. 16 times larger than Lsun
D. 64 times larger than Lsun

D. 64 times larger than Lsun

Modern stellar spectral types (like OBAFGKM)
represent a sequence of changing

A. Temperatures
B. Absolute magnitudes
C. Chemical compositions
D. Pressures

A. Temperatures

Compared to a star in the middle of the H-R diagram, a star in the upper right part of the diagram is

A. Smaller and fainter
B. Larger and fainter
C. Hotter and brighter
D. Larger and cooler

D. Larger and cooler

The interstellar medium is made up of matter in the form of

A. Hydrogen and dust
B. Oxygen and carbon
C. Hydrogen and iron
D Water and ices

A. Hydrogen and dust

What is the distance to a star with an apparent magnitude of +7 and an absolute magnitude of +42

A. 100pc
B. 25 pc
C. 40 pc
D. 1000 light years

C. 40 pc

All the elements heavier than iron are made

A. In the center of the Sun
B. In nebulae
C. In supernova explosions
D. In nova explosions

C In supernova explosions

Star clusters help us to learn about the evolution of stars because stars in a cluster are

A. About the same temperature
B. About the same mass
C. About the same spectral type
D. About the same age

D. About the same age

What are the bluish clouds of gas around the stars in Slide 3?

A. a supernova
B. a planetary nebula
C. reflection nebula
D. an emission nebula

C. reflection nebula

A star is found to have a parallax of 1.0 arcseconds. What is the distance to this star?

A. 1 parsec
B. 4 light years
C. 10 parsecs
D. 2 parsecs

A. 1 parsec

The beautiful object shown on slide 32 is the envelope of a Sun-like star as it finally runs out of fuel. It is

A. a planetary nebula
B. a supernova explosion
C. a nova explosion
D. a red giant star

A. a planetary nebula

What is the object at the center o the Ring Nebula on Slide 2?

A. High mass main sequence star
B. A supernova
C. A white dwarf object
D. A neutron star

C. A white dwarf object

The total energy output emitted at all wavelengths by a star is

A. The parallax
B. The apparent magnitude
C. The temperature
D. The luminosity

D. The luminosity

What is a characteristic of a black hole?

A. They are invisible and can never be detected by astronomers
B. They only appear in starless dark areas of the milky way
C. They suck in planets and stars, no matter where they are
D. They have a size that depends on their mass

D. They have a size that depends on their mass

From the beginning, how long can a star like the Sun keep burning hydrogen in its core?

A. 10,000 years
B. 10 billion years
C. 200 billion years
D. 1 million years

B. 10 billion years

A lower limit to the mass of a star exists because

A. A star must have enough mass to become a black hole
B. A star must have enough mass to ignite hydrogen reactions
C. The need enough mass for gravity to contract them into spheres
D. A star must have enough mass to fuse iron in the core

B. A star must have enough mass to ignite hydrogen reactions

The star Bellatrix has a luminosity of 10,000 suns and the star Altair has a luminosity of 10 suns. If both stars are on the main sequence, then it follows that

A. Bellatrix is smaller than Altair
B. Bellatrix is fainter than Altair
C Bellatrix is hotter than Altair
D. Bellatrix is closer than Altair

C Bellatrix is hotter than Altair

Most known star masses have been determined from observations of single-star systems

A. True
B. False

B. False

Most stars form because of collisions of other stars

A. True
B. False

B. False

Supermassive black holes exist at the centers of star clusters

A. True
B. False

B. False

A star of apparent magnitude +3 looks brighter than on of apparent magnitude +6.

A. True
B. False

A. True

The brightest stars visible in the night sky are found in the lower part of the H-R diagram.

A. True
B. False

B. False

The sun will get dimmer as it begins to run out of hydrogen fuel in its core.

A. True
B. False

B. False

According to general relativity, space is warped or curved by mass.

A. True
B. False

A. True

The best place to search for black holes is in a region of space that

A. has strong x-ray emission
B. is dark and empty
C. is cooler than its surroundings
D. has recently lost some stars

A. Has strong x-ray emissions

Measurements show a certain star has a very low luminosity (0.0001 times the sun's) while its temperature is quite hot (20,000K) How can this be?

A. It must be quite small in size
B. It must be a main sequence star
C. It must be quite large in size
D. It must e a brown dwarf and not a regular star

A. It must be quite small in size

What critical event must occur in order for a protostar to become a main sequence star?

A. The cloud reaches a certain size
B. Nuclear reactions begin in the core
C. The cloud forms planets around it
D. The protostar first becomes small and cold

B. Nuclear reactions begin in the core

Which of the following objects has the highest density?

A. A neutron star
B. Red giants
C. Main sequence stars
D. White dwarfs
E. Black holes

E. Black holes

While a star is a red giant, what is the primary nuclear reaction in the core?

A. Hydrogen -> Uranium + Energy
B. Helium + Energy -> Hydrogen
C. Helium -> Carbon + Energy
D. Hydrogen -> Oxygen + Energy

C. Helium -> Carbon + Energy

For a massive star, what is the final object left behind in the image above (slide 4)?

A. Planetary nebula
B. White dwarf
C. Red supergiant
D. Neutron star

D. Neutron star

Two stars A and B appear the same brightness in the sky but star B is intrinsically brighter. Which star is more distant?

A. Star A
B. Star B
C. Both have equal distance

B. Star B

White dwarfs are less luminous than red giants because

A. White dwarfs are hotter
B. White dwarfs are closer
C. White dwarfs are smaller
D. White dwarfs are denser
E. All of the above

C. White dwarfs are smaller

What determines the lifetime of of a main sequence star on the H-R diagram?

A. Its composition
B. Its velocity
C. Its distance
D. The number of companion stars orbiting it
E. Its mass

E. Its mass

The characteristics of red supergiant stars are

A. Brightness of 20,000 suns and a diameter of about Mars' orbit
B. The brightness of the sun and size of about Mercury's orbit
C. Brightness of about 1 million suns and a diameter of the whole solar system
D. Brightness of 10,000 suns and a diameter of 1/10 of that sun

A. Brightness of 20,000 suns and a diameter of about Mars' orbit

What is the significance of the Turn-off point for a star cluster?

A. It tells which stars might be binary stars
B. It tells the composition of the star cluster
C. It tells the position of the star cluster
D. It tells the age of a star cluster

D. It tells the age of a star cluster

Which type of star is most common?

A. Main sequence
B. Red giants
C. Supergiants
D. White dwarfs

A. Main sequence

Stellar parallax measurements are used in astronomy to determine which of the following properties of stars?

A. Colors
B. Distances
C. Speeds
D. Temperatures
E. Compositions

B. Distances

Two stars have the same luminosity. Star b is three times farther away than star a. Compared to star a, star b will look

A. 9 times fainter
B. 3 times brighter
C. 9 times brighter
D. 50 times fainter
E. both will look equally bright

A. 9 times fainter

A white dwarf is composed primarily of

A. Silicon and neon
B. Carbon and oxygen
C. Iron
D. Cosmic rays

B. Caron and oxygen

Cool stars can be very bright if they very

A. small
B. hot
C. large
D. close to the solar system

C. large

A star like the sun will end up as which kind of object

A. blue giant
B. white dwarf
C. binary star
D. red dwarf

B. white dwarf