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Astrophysics
Classification of Stars
Stellar Spectral Classes
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Created by
Harry Parker
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Cards (49)
Who categorised the spectral classes used today?
Annie Jump-Cannon
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How many temperature classes did Annie Jump-Cannon create?
Seven
temperature classes
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What are the spectral classes in order?
O
B
A
F
G
K
M
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What intrinsic colour corresponds to spectral class O?
Blue
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What is the temperature range for spectral class O?
25,000
–
50,000
K
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What prominent absorption lines are found in spectral class O?
He
, He, H
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What intrinsic colour corresponds to spectral class B?
Blue
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What is the temperature range for spectral class B?
11,000
–
25,000
K
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What prominent absorption lines are found in spectral class B?
He
, H
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What intrinsic colour corresponds to spectral class A?
Blue-white
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What is the temperature range for spectral class A?
7500
–
11,000
K
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What prominent absorption lines are found in spectral class A?
H (strongest),
ionised metals
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What intrinsic colour corresponds to spectral class F?
White
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What is the temperature range for spectral class F?
6000
–
7500
K
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What prominent absorption lines are found in spectral class F?
Ionised metals
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What intrinsic colour corresponds to spectral class G?
Yellow-white
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What is the temperature range for spectral class G?
5000
–
6000
K
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What prominent absorption lines are found in spectral class G?
Ionised
and neutral
metals
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What intrinsic colour corresponds to spectral class K?
Orange
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What is the temperature range for spectral class K?
3500
–
5000
K
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What prominent absorption lines are found in spectral class K?
Neutral metals
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What intrinsic colour corresponds to spectral class M?
Red
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What is the temperature range for spectral class M?
Less than
3500 K
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What prominent absorption lines are found in spectral class M?
Neutral atoms,
TiO
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How does the intrinsic colour of a star relate to its temperature?
Intrinsic colour correlates with peak emission wavelength
Peak emission wavelength is determined by temperature
Described by
Wien's law
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What happens to atoms at low temperatures in stars?
Not enough energy to
excite
atoms
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What happens to atoms at higher temperatures in stars?
Atoms have too much energy to form
molecules
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What is found in the atmospheres of the hottest stars?
Hydrogen
and
helium
in higher abundance
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Why are the spectral lines of the hottest stars dominated by hydrogen and helium?
Due to their higher
abundance
in atmospheres
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What is the significance of the Balmer series in astronomy?
Involves
electron transitions
to/from
n = 2
Wavelengths are in the
visible spectrum
Important for studying hydrogen and helium
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How does the prominence of Balmer lines vary among spectral classes?
Depends on the
surface temperature
of stars
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What is the prominence of Balmer lines in spectral class O?
Weak
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Why are Balmer lines weak in spectral class O?
Star's atmosphere too hot for
hydrogen
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What is the prominence of Balmer lines in spectral class B?
Slightly
stronger
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What is the prominence of Balmer lines in spectral class A?
Strongest
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What is the prominence of Balmer lines in spectral class F?
Weak
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What is the prominence of Balmer lines in spectral class G?
Very
weak
/
none
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What is the prominence of
Balmer
lines in spectral class
K
?
None
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What stars are included in the Winter Triangle?
Procyon
,
Betelgeuse
,
Sirius
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What type of star is Betelgeuse?
Type
M star
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