Astronomy Quiz week 7 – Flashcards
Unlock all answers in this set
Unlock answersquestion
Which two energy sources can help a star maintain its internal thermal pressure?
answer
nuclear fusion and gravitational contraction.
question
The following questions refer to the sketch below of an H-R diagram for a star cluster.
Based on its main-sequence turnoff point, the age of this cluster is
answer
about 10 billion years.
question
What did Carl Sagan mean when he said that we are all "star stuff"?
answer
that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores.
question
Which event marks the beginning of a supernova?
answer
the sudden collapse of an iron core into a compact ball of neutrons.
question
When does a star become a main-sequence star?
answer
A star becomes a main-sequence star when the rate of hydrogen fusion within the star's core becomes high enough to balance the rate at which the star radiates energy into space.
question
Which of the following statements about brown dwarfs is not true?
answer
Brown dwarfs will eventually collapse to become white dwarfs.
question
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) helium core?
answer
iv
question
Refer to the labels (a) through (e) on the following sketch of an H-R diagram. [Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choices (c) or (d) offer better answers to the question than (a), use the best choice.]
Which group represents stars that are cool and dim?
answer
D
question
Refer to the labels (a) through (e) on the following sketch of an H-R diagram. [Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choices (c) or (d) offer better answers to the question than (a), use the best choice.]
Which group represents stars of the largest radii?
answer
E
question
Refer to the labels (a) through (e) on the following sketch of an H-R diagram. [Note that choice (a) refers to the entire main sequence, while (c) and (d) refer to only small parts of the main sequence. If choices (c) or (d) offer better answers to the question than (a), use the best choice.]
Which group represents the most common type of stars?
answer
D
question
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
Which stage lasts the longest?
answer
iii
question
This diagram represents the life track of a 1 solar mass star. Refer to the life stages labeled with roman numerals.
During which stage does the star have an inert (non-burning) carbon core surrounded by shells of helium and hydrogen burning?
answer
viii
question
Where would a brown dwarf be located on an H-R diagram?
answer
It would be located below and to the right of the lowest part of the main sequence.
question
Which of the following lists the stages of life for a low-mass star in the correct order?
answer
protostar, main-sequence star, red giant, planetary nebula, white dwarf.
question
When a main-sequence star exhausts its core hydrogen fuel supply
answer
the core shrinks while the rest of the star expands.
question
The main source of energy for a star as it grows in size to become a red giant is
answer
hydrogen fusion in a shell surrounding the central core.
question
The ultimate fate of our Sun is to
answer
become a white dwarf that will slowly cool with time.
question
The following questions refer to the sketch below of an H-R diagram for a star cluster.
Consider the star to which the arrow points. How is it currently generating energy?
answer
by hydrogen shell burning around an inert helium core.
question
What type of star is our Sun?
answer
low-mass star.
question
No stars are expected with masses greater than 150 times our Sun because
answer
they would generate so much power that they would blow themselves apart.
question
Which of the following statements about degeneracy pressure is not true?
answer
Degeneracy pressure varies with the temperature of the star.
question
What happens when a star exhausts its core hydrogen supply?
answer
Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
question
Compared to the star it evolved from, a red giant is
answer
cooler and brighter.
question
At approximately what temperature can helium fusion occur?
answer
100 million K.
question
Why does a star grow larger after it exhausts its core hydrogen?
answer
Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
question
How many helium nuclei fuse together when making carbon?
answer
3.
question
What is a planetary nebula?
answer
the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star.
question
What happens to the core of a star after a planetary nebula occurs?
answer
It becomes a white dwarf.
question
Which of the following sequences correctly describes the stages of life for a low-mass star?
answer
protostar, main-sequence, red giant, white dwarf.
question
Compared to the star it evolved from, a white dwarf is
answer
hotter and dimmer.
