Astro 7N Exam 2 ACTUAL EXAM QUESTIONS
WITH ANSWERS 2026/2027 GRADED A+
• Hydrogen-2+proton=________+energy -✓✓ Helium-3
• Which 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 will have the shortest lifetime on the main sequence? -✓✓ main sequence star
with surface temperature of 20,000K
• Many of the 100 brightest 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 at the same distance as a .2-solar-mass main
sequence star. Which star appears brighter? -✓✓ the 2 solar mass star appears brighter
• The temperature of the photosphere of the sun is closest to... -✓✓ 6,000K
• An estimate of the number of communicating/technological civilizations that we expect
in our Galaxy would have 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, which of the planets would be in its habitable zone? -✓✓
Jupiter
• What is the exoplanet's orbital period, and the percent brightness drop in light, for the
case in the image above? -✓✓ 5 days and 0.30%
• How do astronomers measure the temperature of stars? -✓✓ by looking at which
absorption lines are present in the star's spectrum
• In the inverse square law activity, what would the wattage of the top lightbulb need to
be, such that it appeared as bright as the bottom lightbulb which is a 25-watt bulb? -✓✓
100 watts
• The largest fraction of nearby stars (e.g. within 100 light years) are: -✓✓ red main
sequence stars
• Which of the stars in the diagram above is the hottest? -✓✓ D
, • If they were all formed at the same time, which of the stars in the diagram will live the
longest? -✓✓ B
• 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 II
supernova, black hole
• Star A is 9 times more luminous than Star B. The two stars appear the same
brightness. What is true about their distances? -✓✓ star A is 3 times farther away than
star B
• In the p-p chain, what particles must be input in order to produce one 4He nucleus? -
✓✓ 6 protons, but 2 of them are returned when the 4He is produced
• 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? -✓✓ a neutron star
• A galaxy has an H-alpha emission line observed at a wavelength 10 percent larger
than the rest wavelength of H-alpha. What is the redshift of the galaxy? -✓✓ 0.1
• What is in this image? -✓✓ supernova remnant
• Which is most luminous? -✓✓ quasar
• Which contains the most stars? -✓✓ a spiral galaxy
• Galaxy A appears twice the angular size of Galaxy B. Assuming the two galaxies have
the same physics size in kiloparsecs, which of the following is true? -✓✓ Galaxy B is 2
times farther away than galaxy A
WITH ANSWERS 2026/2027 GRADED A+
• Hydrogen-2+proton=________+energy -✓✓ Helium-3
• Which 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 will have the shortest lifetime on the main sequence? -✓✓ main sequence star
with surface temperature of 20,000K
• Many of the 100 brightest 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 at the same distance as a .2-solar-mass main
sequence star. Which star appears brighter? -✓✓ the 2 solar mass star appears brighter
• The temperature of the photosphere of the sun is closest to... -✓✓ 6,000K
• An estimate of the number of communicating/technological civilizations that we expect
in our Galaxy would have 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, which of the planets would be in its habitable zone? -✓✓
Jupiter
• What is the exoplanet's orbital period, and the percent brightness drop in light, for the
case in the image above? -✓✓ 5 days and 0.30%
• How do astronomers measure the temperature of stars? -✓✓ by looking at which
absorption lines are present in the star's spectrum
• In the inverse square law activity, what would the wattage of the top lightbulb need to
be, such that it appeared as bright as the bottom lightbulb which is a 25-watt bulb? -✓✓
100 watts
• The largest fraction of nearby stars (e.g. within 100 light years) are: -✓✓ red main
sequence stars
• Which of the stars in the diagram above is the hottest? -✓✓ D
, • If they were all formed at the same time, which of the stars in the diagram will live the
longest? -✓✓ B
• 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 II
supernova, black hole
• Star A is 9 times more luminous than Star B. The two stars appear the same
brightness. What is true about their distances? -✓✓ star A is 3 times farther away than
star B
• In the p-p chain, what particles must be input in order to produce one 4He nucleus? -
✓✓ 6 protons, but 2 of them are returned when the 4He is produced
• 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? -✓✓ a neutron star
• A galaxy has an H-alpha emission line observed at a wavelength 10 percent larger
than the rest wavelength of H-alpha. What is the redshift of the galaxy? -✓✓ 0.1
• What is in this image? -✓✓ supernova remnant
• Which is most luminous? -✓✓ quasar
• Which contains the most stars? -✓✓ a spiral galaxy
• Galaxy A appears twice the angular size of Galaxy B. Assuming the two galaxies have
the same physics size in kiloparsecs, which of the following is true? -✓✓ Galaxy B is 2
times farther away than galaxy A
