Astro 7N Exam 2 Questions and
Answers
A high luminosity star
✓ ~~~Emits more light than a low-luminosity star
If a red giant appears the same brightness as a red main sequence star, which one
is farther away?
✓ ~~~The red giant
The heaviest nuclei of all are formed...
✓ ~~~During a supernova explosion
Hydrogen-2 + proton = ____ + energy:
✓ ~~~Helium-3
Which of the following has the smallest radius?
✓ ~~~Neutron star
Why does the main sequence part of a star's life end?
✓ ~~~The hydrogen in the core is exhausted.
Which of the following will have the shortest lifetime on the main sequence?
✓ ~~~Main sequence star with surface temperature 20000 K
,Many of the brightest 100 stars viewed from Earth are not on the main sequence
(even though most stars are) because...
✓ ~~~The most luminous stars are giants and supergiants that have already finished their
main sequence lifetimes
A 2-solar-mass main sequence star is the same distance as a 0.2-solar-mass main
sequence star. Which star appears brighter?
✓ ~~~The 2 solar mass main sequence star appears brighter
The temperature of the photosphere of the Sun is closest to...
✓ ~~~6000 Kelvin
An estimate of the number of communicating/technological civilizations that we
expect in our Galaxy would be a larger number if...
✓ ~~~The average number of planets that could support life for each star were larger
If the sun had twice its mass, then which of these planets would be in its habitable
zone?
✓ ~~~Jupiter
how do astronomers measure the temperature of stars?
✓ ~~~By looking at which absorption lines are present in the star's spectrum.
The largest fraction of nearby stars (e.g. within 100 light years) are...
✓ ~~~Red main sequence stars
, The parallax angle of a nearby star is measured to be 0.02 arcseconds. What is the
distance to the star?
✓ ~~~50 parsecs
Which of the following is the sequence of events for a 40-solar mass star (one of the
most-massive stars)?
✓ ~~~Stellar nursery, protostar, blue star on main sequence, Type 2 supernova, black hole
Star A is 9 times as luminous as Star B. The two stars appear the same brightness.
What is true about their distance?
✓ ~~~Star A is 3 times farther away than Star B.
What is the name of the slightly cooler layer of the Sun just outside the photosphere?
✓ ~~~Chromosphere
How does a star move on the H-R diagram during the period of time it is converting
hydrogen to helium in its core?
✓ ~~~It remains nearly fixed at a certain point on the main sequence and does not move on
the H-R diagram.
If the entire mass of Earth were concentrated in a region the size of a marble, the
resulting object would be...
✓ ~~~A black hole
Which is the smallest object?
Answers
A high luminosity star
✓ ~~~Emits more light than a low-luminosity star
If a red giant appears the same brightness as a red main sequence star, which one
is farther away?
✓ ~~~The red giant
The heaviest nuclei of all are formed...
✓ ~~~During a supernova explosion
Hydrogen-2 + proton = ____ + energy:
✓ ~~~Helium-3
Which of the following has the smallest radius?
✓ ~~~Neutron star
Why does the main sequence part of a star's life end?
✓ ~~~The hydrogen in the core is exhausted.
Which of the following will have the shortest lifetime on the main sequence?
✓ ~~~Main sequence star with surface temperature 20000 K
,Many of the brightest 100 stars viewed from Earth are not on the main sequence
(even though most stars are) because...
✓ ~~~The most luminous stars are giants and supergiants that have already finished their
main sequence lifetimes
A 2-solar-mass main sequence star is the same distance as a 0.2-solar-mass main
sequence star. Which star appears brighter?
✓ ~~~The 2 solar mass main sequence star appears brighter
The temperature of the photosphere of the Sun is closest to...
✓ ~~~6000 Kelvin
An estimate of the number of communicating/technological civilizations that we
expect in our Galaxy would be a larger number if...
✓ ~~~The average number of planets that could support life for each star were larger
If the sun had twice its mass, then which of these planets would be in its habitable
zone?
✓ ~~~Jupiter
how do astronomers measure the temperature of stars?
✓ ~~~By looking at which absorption lines are present in the star's spectrum.
The largest fraction of nearby stars (e.g. within 100 light years) are...
✓ ~~~Red main sequence stars
, The parallax angle of a nearby star is measured to be 0.02 arcseconds. What is the
distance to the star?
✓ ~~~50 parsecs
Which of the following is the sequence of events for a 40-solar mass star (one of the
most-massive stars)?
✓ ~~~Stellar nursery, protostar, blue star on main sequence, Type 2 supernova, black hole
Star A is 9 times as luminous as Star B. The two stars appear the same brightness.
What is true about their distance?
✓ ~~~Star A is 3 times farther away than Star B.
What is the name of the slightly cooler layer of the Sun just outside the photosphere?
✓ ~~~Chromosphere
How does a star move on the H-R diagram during the period of time it is converting
hydrogen to helium in its core?
✓ ~~~It remains nearly fixed at a certain point on the main sequence and does not move on
the H-R diagram.
If the entire mass of Earth were concentrated in a region the size of a marble, the
resulting object would be...
✓ ~~~A black hole
Which is the smallest object?
