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ASTRO 7N Exam 2
QUESTIONS AND 100% CORRECT DETAILED
ANSWERS
How is spectral class determined? - ANSWER-using the
absorption spectrum, where absorption lines from different
chemical elements with different levels of ionization arise
at different temperatures
H-R diagram vertical axis - ANSWER-luminosity,
expressed in terms of the luminosity of the sun ( "L⊙" )
What is the closest star and how far is it from the sun? -
ANSWER-Alpha centauri
4.3 light years (1.35 parsecs) from the sun
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Part of triple star system, with its brightest member similar
to sun
Properties of nearest stars - ANSWER-cool
Dim
Fall on the lower right of the H-R diagram
What is the brightest star in the nighttime sky? -
ANSWER-Sirius the Dog Star
Twice as massive as Sun
It has a binary companion star, a white dwarf
Properties of "brightest stars" - ANSWER-varied properties
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Red and blue, low and high luminosity, some on the lower
right of H-R diagram, but others near where the sun is,
some on the upper left and some on the upper right ( red
giant region)
What are the "brightest stars" biased towards? -
ANSWER-stars that already have high luminosities, so
they appear bright to us even at large distances; we
simply cannot see low-luminosity stars if they are too far
away (even in great number)
Properties of a star - ANSWER-luminosity, mass, size,
temperature, and age
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Sizer and temperature directly affect luminosity, as in: L ∝
R^2 x T^4 - ANSWER-- a larger size = larger light-emitting
surface area = greater luminosity
- higher temperature = much greater luminosity (also
peaks in bluer colors)
Where are the main sequence stars located on the HR
Diagram? - ANSWER-in a band from lower right across to
upper left - around the slightly -wavy red line in the
example H-R diagram
What are stars during in their cores on when on the main
sequence? - ANSWER-Hydrogen and helium (by the p-p
chain)
ASTRO 7N Exam 2
QUESTIONS AND 100% CORRECT DETAILED
ANSWERS
How is spectral class determined? - ANSWER-using the
absorption spectrum, where absorption lines from different
chemical elements with different levels of ionization arise
at different temperatures
H-R diagram vertical axis - ANSWER-luminosity,
expressed in terms of the luminosity of the sun ( "L⊙" )
What is the closest star and how far is it from the sun? -
ANSWER-Alpha centauri
4.3 light years (1.35 parsecs) from the sun
,2|Page
Part of triple star system, with its brightest member similar
to sun
Properties of nearest stars - ANSWER-cool
Dim
Fall on the lower right of the H-R diagram
What is the brightest star in the nighttime sky? -
ANSWER-Sirius the Dog Star
Twice as massive as Sun
It has a binary companion star, a white dwarf
Properties of "brightest stars" - ANSWER-varied properties
,3|Page
Red and blue, low and high luminosity, some on the lower
right of H-R diagram, but others near where the sun is,
some on the upper left and some on the upper right ( red
giant region)
What are the "brightest stars" biased towards? -
ANSWER-stars that already have high luminosities, so
they appear bright to us even at large distances; we
simply cannot see low-luminosity stars if they are too far
away (even in great number)
Properties of a star - ANSWER-luminosity, mass, size,
temperature, and age
, 4|Page
Sizer and temperature directly affect luminosity, as in: L ∝
R^2 x T^4 - ANSWER-- a larger size = larger light-emitting
surface area = greater luminosity
- higher temperature = much greater luminosity (also
peaks in bluer colors)
Where are the main sequence stars located on the HR
Diagram? - ANSWER-in a band from lower right across to
upper left - around the slightly -wavy red line in the
example H-R diagram
What are stars during in their cores on when on the main
sequence? - ANSWER-Hydrogen and helium (by the p-p
chain)
