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ASTRO 7N EXAM 3-2025/2026 QUESTIONS WITH 100%
DETAILED ANSWERS
Hertsprung-russel diagram - answer-shows the brightness
of the stars on a scale. Plots the luminosity (y-axis)
against the star's surface temperature (x-axis) *the surface
temperature gets hotter from right to left, so the hotter
stars are bluer and the cooler stars are redder. The closer
that you get to the y axis, the hotter the surface
temperature gets
The spectral class of stars - answer-from hottest to coldest
they are ranked obafgkm
Obafgkm - answer-oh be a fine girl kiss me
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We determine the spectral class of a star using the -
answer-absorption spectrum
The vertical axis of the hertsprung-russel diagram -
answer-represents the luminosity expressed in terms of
the luminosity of the sun
A 2-solar mass main sequence star is at the same
distance as a 0.2-solar mass main sequence star. Which
star appears brighter?
A: depends on the phase of the moon
B: the 2 solar mass main sequence star appears brighter
C: the stars are approximately the same brightness
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D: the 0.2 solar mass main sequence star appears
brighter
E: we cannot tell with the information given - answer-b: the
2 solar mass main sequence star appears brighter
The temperature of the photosphere of the sun is closest
to ...
A: 107 kelvin
B: 106 kelvin
C: 100 kelvin
D: 600,000 kelvin
E: 6000 kelvin - answer-e: 6000 kelvin
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An estimate of the number of communicating/technological
civilizations that we expect in our galaxy would have a
larger number if ...
A: the average lifetime of a communicating civilization was
smaller
B: the star formation rate in our galaxy was smaller
C: the average number of planets that could support life
for each star was larger
D: it was more difficult for life to develop intelligence, once
life had formed
E: a smaller percentage of stars formed planets - answer-
c: the average number of planets that could support life for
each star was larger
ASTRO 7N EXAM 3-2025/2026 QUESTIONS WITH 100%
DETAILED ANSWERS
Hertsprung-russel diagram - answer-shows the brightness
of the stars on a scale. Plots the luminosity (y-axis)
against the star's surface temperature (x-axis) *the surface
temperature gets hotter from right to left, so the hotter
stars are bluer and the cooler stars are redder. The closer
that you get to the y axis, the hotter the surface
temperature gets
The spectral class of stars - answer-from hottest to coldest
they are ranked obafgkm
Obafgkm - answer-oh be a fine girl kiss me
,2|Page
We determine the spectral class of a star using the -
answer-absorption spectrum
The vertical axis of the hertsprung-russel diagram -
answer-represents the luminosity expressed in terms of
the luminosity of the sun
A 2-solar mass main sequence star is at the same
distance as a 0.2-solar mass main sequence star. Which
star appears brighter?
A: depends on the phase of the moon
B: the 2 solar mass main sequence star appears brighter
C: the stars are approximately the same brightness
,3|Page
D: the 0.2 solar mass main sequence star appears
brighter
E: we cannot tell with the information given - answer-b: the
2 solar mass main sequence star appears brighter
The temperature of the photosphere of the sun is closest
to ...
A: 107 kelvin
B: 106 kelvin
C: 100 kelvin
D: 600,000 kelvin
E: 6000 kelvin - answer-e: 6000 kelvin
, 4|Page
An estimate of the number of communicating/technological
civilizations that we expect in our galaxy would have a
larger number if ...
A: the average lifetime of a communicating civilization was
smaller
B: the star formation rate in our galaxy was smaller
C: the average number of planets that could support life
for each star was larger
D: it was more difficult for life to develop intelligence, once
life had formed
E: a smaller percentage of stars formed planets - answer-
c: the average number of planets that could support life for
each star was larger
