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The Manga Guide to the Universe by Verte Corp., Kiyoshi Kawabata, Kenji Ishikawa

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104 Chapter 2 From the Solar System to the Milky Way
Let me explain
the galaxy to
you a lile
beer.
Um, is she
okay?
She's fine.
This always
haens.
The diameter of the disc part
is 100,000 light-years.
100,000 light-
years? What in
the world are
you talking
about?!
It's the distance
that light travels
in 100,000 years!
That doesn’t
help at a.
Isti have no
idea what that
means.
Te me in miles,
ft, even
centimeters!!
I refuse to
respond to
this fld of
questions.
1 light-year is
9.4607309725808
× 10
15
meters =
9.46triion km =
5.88 triion miles=
aroxi mately
63,240 astronomical
units(AU)!
So 1 light-year
is roughly
6triion miles.
Even in
miles,
I can't
wrap
my head
around
it.
The Size of the Milky Way Galaxy
As I said before, the Milky
Way galaxy is a disc-shaped
aregation of stars, which
bulges at the center.
Don't spit
on me.
Ding!
6
t
r
i
i
o
n
m
i
l
e
m
a
r
a
t
h
o
n
The Size of the Milky Way Galaxy 105
We, you know
that 1 astronomical
unit (AU) is the mean
distance betwn
Earth and the Sun.
The orbital radius
of the outermost
planet, Neptune,
is aroximately
30AU.
This is
aroximately 30
times the distance
betwn the Sun
and Earth.
It may be easier to
understand if you
compare it with
something else.
We, then, is the
diameter of the
solar system
30 × 2 = 60 AU?
No. More than
1triion comets are
floating in the Oort
cloud, which extends
to an area 1.6 light-
years from the Sun.
Therefore, the actual
diameter of the solar
system is 3.2 light-
years, or aroximately
200,000 AU.
Since the solar
system is 3.2 light-
years acro and
the galaxy is 100,000
light-years acro...
...the Galaxy is
aroximately
30,000 times
larger!
How about that?
Now you know
how vast the
Galaxy is!
Kaa!
So you
established
thescale...
so what?
1 astronomical
unit (AU)
Earth
Sun
Oort
cloud
Sun and
planets
Neptune
29

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