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School
Stephen F Austin State University *
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Course
105
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
6
Uploaded by husbandjc
Stellar
Distance
Figure
Distant
Stars
Figure
2
A
Jull
Nea
y
Star
1
B'
View
through
a
Telescope
Nearby
Star
'A'
Earth
January
1
Page
69
Astronomy
i
103
Laboratory
Manual
Figure
3
8
co
Page
70
Astronomy
1103
Laborato
Manual
Name
Lab
Section
Date
Questions
1.
Is
a
parsec
a
unit
of
distance,
an
angular
unit,
or
a
unit
of
time?
Of
Visearr.-e
2.
For
a
star
with
a
parallax
of
0.167
arc
seconds
(p
0.167
arc
sec),
what
is
its
distance
from
us
in
light-years?
M
S
iöghHltaCS
3.
Consider
two
stars
that
are
different
distances
from
the
Earth.
Star
1
has
a
parallax
1/5
as
large
as
Star
2.
Which
star
is
farther
away?
How
much
farther?
'I
avva_q
HØ.JO
5+ar
Z
4.
Find
the
distance
in
light-years
to
the
star
Wolf
359.
The
necessary
information
to
make
this
calculation
can
be
found
in
the
telescopic
observations
shown
below.
(Hint:
Use
a
ruler
to
measure
the
parallax
displacement
in
centimeters,
then
convert
it
to
arc
seconds
and
don't
forget,
parallax
is
1/2
the
measured
displacement.)
Show
your
work!
Telescope
View
Position
of
Wolf
359
on
March
1
RA
IOh
56m
Dec
01'
Star
field
around
the
nearby
red
dwarf
star
"Wolf
359"
Position
of
Wolf
359
on
Seotember
1
These
two
stars
are
very
distant
background
stars
that
have
a
measured
angular
separation
of
1.5
arc
seconds.
Page
72
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Name
Procedure
Stellar
Distance
Lab
Section
1,
Study
carefully
the
two
plots
on
pages
81
and
82.
One
plot
is
a
color-magnitude
diagram
of
the
Pleiades
cluster
and
the
other
is
a
standard
HR
diagram.
2.
Determine
the
distance
modulus
for
the
Pleiades
Star
cluster.
Distance
Modulus
=
mv
—
MV
Method
1:
In
this
exercise
you
will
determine
the
color
index,
the
apparent
magnitude
and
the
absolute
magnitude
for
each
of
the
six
stars
listed
in
the
table
below.
1.
Use
the
color-maqnitude
plot
to
find
the
color
index
(mb
—
mv)
and
apparent
magnitude
(mv)
for
each
star
listed
(stars
are
labeled
on
plot
by
their
Eggen
number).
Enter
the
values
in
table
below.
2.
Now
determine
the
absolute
magnitude
(MD
for
each
star
using
the
standard
HR
diagram
and
its
color-index.
Enter
the
values
in
the
table
below.
3.
Calculate
the
distance
modulus
for
each
star
then
form
an
average
using
the
values
from
all
six
stars.
Color
Apparent
Absolute
Distance
Eggen
#
Index
Magnitude
Magnitude
Modulus
m
9
41
18
20
voo
22
01
7.1
27
1.0
31
Average
Distance
Modulus
=
Page
75
Astronomy
1103
Laboratory
Manuaj
Method
2:
Your
teaching
assistant
will
provide
you
with
a
properly
scaled
standard
HR
diagram
and
a
transparency
of
the
Pleiades
color-magnitude
diagram,
Place
the
color-
magnitude
diagram
over
the
standard
main-sequence
plot
making
sure
the
two
color
index
scales
(ml,
mv)
align.
Now
move
the
top
graph
up
and
down
until
the
color-
magnitude
data
points
best
overlay
the
standard
main-sequence
curve.
Keep
the
color
index
scales
aligned
during
this
process.
Once
the
best
fit
has
been
found,
determine
the
difference
between
the
corresponding
values
of
MV
and
mv
from
the
vertical
axes
of
the
graphs.
This
is
the
distance
modulus.
Distance
Modulus
=
(U
Questions
1.
Calculate
the
distance
to
the
Pleiades
in
both
parsecs
and
light-years
using
the
distance
modulus
values
from
Method
1
and
Method
2
(show
your
work).
distance
modulus
(Method
1)
(e
I
d:
IDx
(0.11/5)
?aO€CS
distance
parsecs
distance
913,
light-years
distance
modulus
(Method
2)
'Ox
10
distance
distance
parsecs
light-years
3
.
fiq
k3uq
Page
76
Stellar
Distance
2.
What
was
the
most
important
assumption
made
for
finding
the
distance
to
the
Pleiades
star
cluster
using
the
above
methods?
Explain,
wc
;tac5
[n
fhL
P/ciadus
are
all
3.
How
would
interstellar
gas
and
dust
affect
your
results?
matt
thum
appar
afmnnuan/
/urkVær
f/uø
4.
Consider
a
star
whose
absolute
magnitude
is
4
and
apparent
magnitude
is
2.
Is
this
star
closer
than
10
parsecs,
farther
than
10
parsecs
or
exactly
10
parsecs
away?
Explain
your
reasoning.
c(ozr
khan/0
parzcs
5.
For
very
distant
star
clusters,
why
must
astronomers
use
the
main-sequence
method
rather
than
the
stellar
parallax
method?
MLHnod
only
woncs
Page
77
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