ASTRO 7N EXAM 2 INTRODUCTION TO
ASTRONOMY CORE CONCEPT REVIEW
AND STEP BY STEP EXPLANATIONS 2026
STUDY GUIDE
◉ If a red giant appears the same brightness as a red main sequence
star, which one is further away?
Answer: the red giant
◉ The heaviest nuclei of all are formed
Answer: during a supernova explosion
◉ Hydrogen-2+proton=________+energy
Answer: Helium-3
◉ Which has the smallest radius?
Answer: neutron star
◉ Why does the main sequence part of a star's life end?
Answer: the hydrogen in the core is exhausted
, ◉ Which will have the shortest lifetime on the main sequence?
Answer: 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...
Answer: 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?
Answer: the 2 solar mass star appears brighter
◉ The temperature of the photosphere of the sun is closest to...
Answer: 6,000K
◉ An estimate of the number of communicating/technological
civilizations that we expect in our Galaxy would have a larger
number if...
Answer: 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?
ASTRONOMY CORE CONCEPT REVIEW
AND STEP BY STEP EXPLANATIONS 2026
STUDY GUIDE
◉ If a red giant appears the same brightness as a red main sequence
star, which one is further away?
Answer: the red giant
◉ The heaviest nuclei of all are formed
Answer: during a supernova explosion
◉ Hydrogen-2+proton=________+energy
Answer: Helium-3
◉ Which has the smallest radius?
Answer: neutron star
◉ Why does the main sequence part of a star's life end?
Answer: the hydrogen in the core is exhausted
, ◉ Which will have the shortest lifetime on the main sequence?
Answer: 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...
Answer: 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?
Answer: the 2 solar mass star appears brighter
◉ The temperature of the photosphere of the sun is closest to...
Answer: 6,000K
◉ An estimate of the number of communicating/technological
civilizations that we expect in our Galaxy would have a larger
number if...
Answer: 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?
