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Description
The Our Galaxy App: Understanding the 3D Nature of Our Galaxy
Bill Tschumy
Amateur astronomers generally know where to find deep sky objects in the night sky, but few are aware of their physical locations within the Galaxy. Our Galaxy is a cross-platform app that helps you understand the structural components of the Galaxy and visualize the locations and physical properties of deep sky objects in and around it. Bill will discuss the creation of Our Galaxy and use the app to illustrate what we know about galactic structure and show where some well known deep sky objects are located within and around it.
Bill Tschumy founded Otherwise Software in 1992 to develop innovative software. Besides programming, Bill’s other interests are amateur astronomy and astronomy education. In 2009 he got the chance to combine his programming skills with his love of astronomy and co-authored SkySafari, one of the most popular astronomy apps for mobile devices and Macintosh. Bill has since left the SkySafari project and is now obsessed with understanding where the deep sky objects we observe are actually located in the Galaxy. The Our Galaxy app is the latest result of his efforts.
A
B
C
B
B
Giving
an
overview
of
what
I'll
be
talking
about
tonight.
First,
I
want
to
talk
about
a
little
motivation.
You
know
why
I
was
interested
in
this
project
and
have
been
interested
in
this
kind
of
project
for
a
long
time
mentioned
how
I
got
started
in
this,
because
it's
a
moderately
interesting
story.
I
think
then
go
through
a
few
basic
facts
about
our
milky
way
galaxy,
and
some
of
this
will
be
familiar
with
to
you.
Some
of
it
won't
be
familiar,
so
hopefully
everybody
will
get
a
chance
to
learn
something.
B
B
And
then
I
want
to
talk
about
plato's
cave
allegory,
which
many
of
you
may
have
heard
of.
But
it's
it's
relevant
here.
I
think
and
then
finally,
some
conclusions
and
again
feel
free
to
unmute
yourself
and
ask
a
question
as
I
go
along.
If
there's
something
that's
not
clear
or
if
I've
made
some
horrible
mistake
or
something
like
that,.
B
I
used
to
have
an
app
that
I
wrote
a
long
time
ago
called
where
is
m13
and
it
was
about
the
same
kind
of
concept
about
where
are
things
in
the
galaxy
and
a
friend
of
mine
talked
me
into
naming
the
app
where's
m13,
because
I
always
that
was
one
of
my
favorite.
You
know
globular
clusters
and
I
always
used
it
as
this
question
of.
Where
is
this
thing
in
our
galaxy?
B
So
we
know
where
it
is
in
the
sky,
it's
up
there
in
the
keystone
of
hercules.
But
where
is
that
in
the
galaxy
you
know?
Who
knows,
and
is
it
even
the
northern
galactic
hemisphere
of
the
southern
galactic
hemisphere?
And
I
guarantee
you
because
I've
done
this.
If
you
ask
you
know
a
hundred
people,
maybe
five
percent
might
have
a
clue
on
it
and
the
rest
people
say
I
don't
know
where
it
is.
B
B
B
Looking
at
when
we
are
looking
at
objects-
and
I
really
got
interested
in
this-
and
so
I
read
his
book
and
he-
the
this
book-
has
a
fatal
fl.
Well,
it's
not
a
fatal
flaw,
but
it's
a
a
serious
flaw.
He
doesn't
have
any
illustrations
and
so
he'd
describe
these
things
and
there'd
be
no
pictures
to
help.
B
Maybe
I
got
interested
in
this
again
and
I
decided
to
maybe
write
an
app
and
I
said:
well,
I'm
a
programmer.
I
can,
you
know,
write
an
app
that
will
help
show
this
stuff,
and
so
I
wrote
this
thing
called.
Where
is
m13,
and
this
is
what
the
user
interface
looked
like,
it
was
written
in
java,
and
so
it
was
cross-platform
by
virtue
of
being
in
java,
and
this
is
what
it
looked
like
it's
nowadays.
B
I
look
at
this
and
it
looks
pretty
crude,
but
back
then
I
thought
it
was
pretty
cool
and
basically
it
showed
just
a
face
on
and
an
edge
on
view
of
the
galaxy
with
the
objects
plotted
on
the
screen
and
it's
kind
of
like
a
like
an
architect
uses.
You
know
two
views
of
a
of
a
building
to
kind
of
you
know
see
it
from
the
top
and
from
the
side,
and
so
I
did
that
and
I
plot
these
things
and
I
found
it
pretty
fascinating.
B
I
sold
this
for
a
number
of
years
until
I
got
involved
in
some
other
projects,
so
that's
where's
m13
when
I
started
doing
sky
safari
after
a
couple
years
in
sky
spring,
we
were
looking
around
for
features
to
put
in
sky
safari,
and
I
said
well,
maybe
I
can
use
my
my
do
something
like
where's
m13.
So
when
you
select
an
object
in
sky
safari,
you
can
say
well
show
this
to
me
in
the
galaxy
view
and
again
it
would
do.
A
B
There
are
some
star
streams
that
appear
to
be
captured
from
other
galaxies
that
you
know
are
coming
in
at
weird
angles
and-
and
you
know
orbit
in
non-expected
ways
around
the
galaxy
and
things
like
that
and,
of
course,
the
globular
clusters
themselves
are
not
in
the
plane,
but
I
can.
I
can
hopefully
talk
about
that
a
little
bit
more
as
we
as
we
go
on
in
this.
B
So
the
image
I
use
in
everything
from
where's
m13
to
the
galaxy
view
to
our
galaxy
is
this,
and
this
was
a
an
artist
rendering
based
upon
data
from
the
spitzer
space
telescope
and
it
took
that
data
and
the
artist
made
its
best
guesses
to
what
our
galaxy
looks
like.
Of
course,
you
know
we,
we
can't
get
a
camera
up
above
the
plane
of
the
galaxy
and
look
down
and
see
what
it
really
looks
like
and
we've
barely
got
anything
out
of
our
solar
system.
B
B
We
know
very
little
about
that
infrared
telescopes
that
you
know
look
back
in
infrared.
They
can
sort
of
see
through
some
of
the
dust
and
kind
of
figure
out
a
little
bit
about
that
and
they're.
You
know
we're
now
learning
more
about
it,
but
this
is
kind
of
you
know.
Very
specula,
even
more
speculative
on
the
other
side
of
our
galactic
core
than
it
is
on
our
side.
B
So
our
galaxy
is
around
100
000
light
years
in
diameter,
some
books
will
say:
150
000,
some
books
will
say:
80
000.,
you
know
they
don't
it's.
It's
not
a
hard
there's,
not
a
hard
line
to
the
the
disc
of
our
galaxy
and
it
kind
of
fades
out,
and
so
the
question
is
well.
Where
do
you?
Where
do
you
say
it
ends?
And
given
that
hundred
thousand
light
years
is
a
nice
round
number?
I
just
use
that
and
a
lot
of
other
people
use
that
too.
B
The
there's
a
galactic
bulge
in
the
center-
it's
not
it's,
not
spherical.
It's
it's!
A
football
shaped
type
thing
about
seven
thousand
light
years
in
that
dimension,
maybe
twenty
thousand
light
years
in
that
dimension
there
and
it's
about
12
000,
light
years
in
thickness.
If
you
look
on
an
edge
on
and
then
our
our
arms
are
our
our
disc
of
our
galaxy,
which
is
called
the
thin
disc,
is
about
1500,
maybe
2
000,
light
years
in
thickness.
B
Of
course
we
like
to
name
things,
so
all
these
arms
have
names,
you
have
the
outer
arm
or
perseus
arm.
This
is
our
arm
is
called
either
the
orion
spur.
Sometimes
it's
called
the
local
arm.
The
next
arm
inward
is
called
the
sagittarius
arm.
Then
the
scutum
centaurus
arm
and
the
normal
arm
is
the
most
inner
one.
B
B
Galactic
longitude
is
measured
along
this
line,
so
zero
galactic
longitude
is
pointing
toward
the
core
of
our
galaxy
and
then
you
measure
around
90
degrees.
Longitude
is
here
so,
if
you're
looking
off
in
that
direction,
sort
of
down
our
own
spiral
arm,
you're,
looking
at
90
degrees,
longitude,
180
degrees,
longitude
over
here
and,
of
course,
270
over
here
and
then,
of
course,
the
north
galactic
poles
at
90
degrees
latitude
in
the
south
galactic
pole
is
minus
90.,
and
so
it's
kind
of
when
I
first
came
across
this.
B
I
thought:
well,
it's
not
really
a
galactic
coordinate
system,
because
it
really
is
it's
it's
centered
on
the
sun,
it's
not
centered
on
the
core
of
the
galaxy,
which
is
kind
of
what
I
might
think
it
would
be.
But
this,
as
it
turns
out,
works
out
very
useful
like
this,
and
of
course
they
do
have
a
another
black
coordinate
system
that
is
centered
on
our
core
and
of
course
back.
Then
they
didn't
really
know
you
know
when
they
first
established.
B
B
B
B
There's
an
object
info
panel,
you
can
pop
up
and
I've
highlighted
the
galactic,
longitude
and
latitude
here.
So
again,
the
angle
from
the
sun
here
up
to
here
is
about
40
41
degrees
up
here
and
it's
59
degrees
from
the
core
of
our
galaxy
on
around
to
where
that
is
and
the
other
thing
that's
kind
of
useful
is
what's
the
distance
from
the
galactic
plane,
and
so
it's
about
15
000,
light
years
above
our
galactic
plane
and,
of
course
up
here.
The
distance
from
earth
is
about
23
000
light
years.
B
B
B
So
it's
a
fairly
simple
user
interface,
as
I
say,
there's
a
there's
a
this
button
in
the
center,
the
lower
toolbar,
there's
galaxy
and
sky,
the
galaxy's
highlighted
if
I
click
on
sky,
that
gives
you
that
sky
view
right
now.
There's
no
objects
other
than
the
stars.
That
are
there
just
for
reference,
but
this
view
doesn't
have
anything
the
object's
displayed
in
it.
B
You
can
save
your
own
custom
views,
but
these
are
built-in
views,
and
so
one
category
is
stars
and
ob
associations,
open
clusters
and
whatnot
tapping
on
that
info
thing
again
little
thing
about
stars
and
you
know
what's
going
on
with
stars,
but
if
you
drill
down
and
tech
on
the
stars
itself,
it'll
show
you
some
different
views
that
I
built
up
for
showing
the
star.
So
if
you
want
to
see
all
the
stars
say
in
that
are
in
our
app
and
again
it's
not.
I
have
stars
down
to
about
6.5
magnitude.
B
B
B
If
I
pan
around
sure
enough,
there's
zero
degrees,
pointing
back
to
our
galactic
core
180
degrees,
of
course,
is
just
the
opposite,
and
I've
labeled
a
few
of
the
bright
stars
here,
so
you
can
kind
of
get
a
sense
of
where
they
are
and
they're
kind
of
you
know.
Obviously
it
makes
sense.
I
mean
you
and
think
of
antares
antares
is
in
scorpius.
Scorpius
is
back.
You
know
near
the
near
the
galactic
core
and
sure
enough.
B
If
you
go
over
here
and
look
at
it,
it's
going
to
be
back
in
near
the
core
there,
so
you
can
see
where
your
other
stars
are
and
beetlejuice
is.
You
know
180
degrees
away,
almost
looking
out
away
from
the
core
of
our
galaxy,
using
the
buttons,
the
plus
and
minus
buttons
along
the
toolbar.
There
you
can
zoom
in.
B
All
the
bright
stars
are
like
a
little
pile
of
salt
there
near
our
sun
and
if
you
think
about
it,
that
makes
sense
stars
far
away
or
dimmer.
So
all
the
bright
stars,
you
think,
would
be
very
close,
and
so
it's
surprising
and
I've
got
maybe
6
000
stars
in
the
database.
That's
all
I
decided
to
put
in
here,
and
so
that's
where
the
brightest
6
000
stars
are
in
our
galaxy.
There's
a
few
way
out
here.
B
B
B
You
might
expect
eventually
you
get
where
you
can
actually
see
the
constellation
as
you
get
close
to
the
sun,
so
that
so
that
the
positioning
is
what
you
expect.
So
here's
the
bright
stars
of
auriga
kind
of
making
a
circle.
Unfortunately,
I
can't
point
on
my
ipad
to
kind
of
there's
no
cursor
here.
I
can
use
to
outline
them,
but
you
can
see
a
circle
star
string.
Cappella
then
going
up
to
the
left
to
then
column
and
on
around
which
are
the
stars
we're
right,
zoom
back
out.
B
B
B
So
here
we'll
show
you,
when
you're
looking
at
a
particular
constellation
again.
These
are
only
constellations
that
intersect
with
the
milky
way
up
in
the
night
sky.
This
is
where
you're
looking
in
the
galaxy
so
cygnus
again
this
little
wedge
for
cygnus
you're.
Looking
down
at
that
arm,
see
a
ryga
over
there
to
the
left,
that's
the
one
we
were
looking
at
previously
off
in
that
direction,
so
this
is
a
good
way
to
start
to
get
a
sense
of.
Oh
I'm!
Looking
in
this
constellation.
Where
am
I
looking
in
the
galaxy?
B
B
So
those
are
the
stars:
I'm
going
to
skip
ob
associations
right
now.
Obi
associations
are
young
young
groupings
of
hot,
o
and
b
stars
that
have
just
recently
formed.
I
mean
I
can
just
briefly
just
show
all
of
the
associations
they
tend
to
be
in
the
spiral
arms
themselves,
because
that's
where
star
formation
is
happening,
but
these
are
all
the
major
ob
associations
we
know
of
in
the
galaxy
and
where
they're
located
in
their
arms,
I
go
to.
B
So
all
these
are
pretty
close
to
the
sun
in
the
same
way
that
the
bright
stars
are
close
to
the
sun.
I
mean
there's,
surely
ob
associations,
you
know
in
all
the
arms
in
all
positions,
the
arms
around
our
in
the
plane
of
the
galaxy.
We
just
can't
see
them
because
they're
obscured
by
dust,
but
this
is
the
main
ones
that
we've
recognized
right
now.
B
And
I
don't
have
that
in
there.
Yes,
the
ob,
the
guy
data
I've
actually
not
seen
new
named
ob
associations
based
upon
it,
although
surely
probably
people
have
done
that
or
are
doing
that
now,
and
I
will
comment
that
a
lot
of
the
objects
I
have
in
here
are
based
upon
the
dr2
version
of
the
gaia
data,
the
first
release
of
gaia
they're
now
up
to
dr3.
A
B
We
get
this
so
again
we
switch
to
an
edge
on
view
here,
but
that's
all
the
recognized
open
clusters
that
I
was
able
to
pull
out
of
simbad
when
I
sort
of
harvest
the
data
out
of
that.
But
again,
if
you
pan,
you
can
start
to
see
where
they're
oriented
here
again
sort
of
zoom
in
on
them
and
again,
some
of
them
this
guy
over
here,
that's
m24.
It's
not
truly
an
open
cluster.
Of
course
it's
a
it's,
but
it's
the
closest
thing.
We
can
call
it
an
open
cluster.
B
I
guess
all
right,
open
cluster
is
the
closest
category.
I
guess,
but
it's
a
it's
a
view
of
that
arm
through
a
hole
in
the
dust
so
that
we
can
sort
of
see
that
into
that
inner
arm
there
and
that's
where
m24
is.
You
know
other
things
if
you're
going
to
just
tap
on
these
objects,
you
can
see
where
these
different
clusters
are
calling
her.
B
B
You
can
actually,
as
many
of
you
might
know,
when
clusters
form
they
form
in
the
plane
and
as
they
age
they
usually
migrate
out
of
the
plane,
or
at
least
the
ones
that
are
out
of
the
plane
tend
to
be
very
old
because
they
sort
of
migrated
out,
and
you
can
show
that
here.
So,
if
you
do
say,
young
open
clusters-
and
I
think
I'd
find
young
open
clusters-
is
things
younger
than
100
million
like
100
million
years?
B
You'll
see
there
that
they've
there's
quite
a
few
of
them,
just
they're
no
longer
concentrated
along
the
midline
of
our
of
our
disk,
but
they're
they're
they've
migrated
off
and
again
that's
what
things
do
they
they
form
in
the
plane
of
the
galaxy
and
then
as
they
get
gravitationally
disturbed
by
you
know,
other
giant
molecular
clouds
and
things
like
that.
They
get
disturbed
and
get
sort
of
migrated
off
from
the
plane
of
our
galaxy.
B
B
B
B
Making
this
database
was
was
a
bit
of
a
chore.
You
can
often
get,
you
know,
coordinates
of
where
a
nebula
is,
but
the
distance
to
it
is
very
often
unknown,
and
you
know
for
imaging
or
looking
after
a
telescope.
It
doesn't
that
doesn't
matter,
you
don't
need
to
know
the
distance.
You
just
need
its
coordinates
in
in
you
know,
re
and
deck,
but
to
plot
it
in
the
galaxy.
B
Of
course,
you
need
to
know
the
distance
and
because
distance
to
nebulae
and
planetary
neglect
are
often
very
hard
to
get,
particularly
for
things
that
are
further
out.
We
just
don't
have
a
distance
to
it,
so
I
had
to
filter
all
these
objects
only
choose
the
ones
that
we
had
a
known
distance
to
there'd
be
a
lot
more.
If
I
didn't
have
that
restriction.
B
And,
of
course,
I
highlighted
m13
because
it's
my
favorite,
so
this
is
again
you
again.
You
hear
that
they
they
hover
around
the
core
of
our
galaxy
like
a
form
of
bees,
and
this
is
it
turn
around
see
these
guys,
and
let
me
also
mention
this
point
I
magnify
the
most
of
these
deep
sky
objects
by
by
a
factor.
B
I
think
these
are
about
eight
times
bigger
than
they
really
are
only
so
because
you
can't
see
them,
otherwise
they
become
little
pinpoints
there
actually
is
a
option
here
under
visibility,
visibility
to
scale
the
deep
sky
objects.
If
I
turn
that
off,
that's
what
they
really
look
like,
if
you
can
see
that
you
can
see
a
little
pinpricks
there,
that's
how
big
they
really
are
relative
to
the
galaxy,
but
that's
kind
of
a
boring
view.
B
B
B
There
it
is
so
this
is
the
ngc
2419
up
in
the
upper
left.
That's
the
intergalactic
wanderer
and
again,
if
you
select
it
hit
info,
you
can
say:
oh
it's!
The
distance
from
earth
is
about
270
000,
light
years
away
from
us
again,
so
you
get
all
the
facts
and
figures
here.
I
also
mentioned
that
as
part
of
the
app
I've
got,
the
thing
on
you
know
search
the
web.
So
if
you
don't
find
the
information
here
you
want
to
or
you
want
to
learn
more
about
it.
B
You
can
always
tap
on
to
see
if
this
works,
so
there
did
a
web
search
for
you
and
brought
up.
So
now
you
can
go
and
pan
and
look
at
that-
and
you
can
look
at
say
you
know
images
of
the
intergalactic
wanderer
and
things
like
that.
We'll
go
back
to
our
app
and
do
that
and
of
course
it's
got
its
other
names
for
it.
B
So
there's
the
intergalactic
water
we
just
looked
at
now:
we've
panned
out
even
further,
so
these
things
are
other
globular
clusters
that
are
actually
part
of
our
galaxy
they're
gravitationally
bound
to
our
galaxy
again.
These
are
mostly
photographic
objects.
You're
not
going
to
see
these
in
most
telescopes,
some
of
the
palomar
objects
you
can.
B
I
know
imagers
love
galaxies
almost
as
much
as
nebula,
so
I've
got
different
groupings
of
galaxies,
so
you
can
kind
of
get
a
sense
of
where
they
are
relative
to
our
galaxy
and
how
far
away
they
are.
We
can
just
first
start
with
all
galaxies.
I
guess
so
now
we-
and
I
should
mention
in
the
upper
left
corner-
is
the
distance
that
we
are
located
from
the
sun.
So
it
gives
you
a
sense
of
kind
of
how
far
away
we
are
looking
back
on
this.
B
B
These
are
all
you
know,
galaxy
groupings
that
are
known
you
can
look
at
the
local
group,
so
you
go
back
in
here
and
say
our
local
group
of
galaxies
so
now
we're
in
only
about
2
million
light
years
away
here,
kept
doing
that,
I
have
a
thing
that,
after
you've
accessed
these
views
about
20
times
it
pops
up
a
rating
thing.
If
you
haven't
rated
it
yet
to
give
you
a
chance,
I
can't
rate
it
because
I'm
the
developer,
so
it
keeps
doing
this
for
me
anyway.
B
B
B
B
B
B
B
So
the
other
thing
I
wanted
to
mention
here,
I'm
almost
done
with
my
my
demo,
this
the
app
let's
talk
about
galactic
structure,
and
this
is
important
enough.
I'd
like
to
go
through
it.
So
there's
there's
five
main
structures
that
I
talk
about
in
the
app
the
thinness,
the
thick
disc,
the
galactic
bulge,
the
stellar
halo
and
the
dark
matter
halo.
B
B
Highlight
that
region
there
with
that
little
kind
of
wall,
so
that's
the
thickness
of
the
thin
disc
of
our
galaxy
right
there
and
again,
the
thin
disc
is
where
most
star
formation
stuff
happens
and
I'm
gonna.
This
is
gonna
sound
like
I'm
reading,
something
because
I
am
because
I'd
like
to
communicate
this
information
to
you.
The
thin
disk
region
refers
to
an
area
about
a
thousand
light
years
above
and
below
the
plane
of
the
galaxy.
B
B
The
thin
disc,
contains
our
sun,
along
with
sirius
vega,
fragile
beetlejuice
and
alpha
centauri.
It's
thought
that
about
96
of
stars
near
the
sun
belong
to
the
thin
disk.
They
come
in
a
variety
of
ages
from
freshly
formed
over
10
billion
years
old.
The
thin
disc
contains
essentially
all
the
galaxy's
non-stellar
material.
B
B
B
B
Okay
again
metallicity
for
those
that
don't
know
has
to
do
with
the
ratio
of
iron
to
hydrogen
atoms
in
the
stars
or
in
whatever
object,
you're
talking
about
and
so
for
stars
early
in
our
in
the
universe's
creation.
The
first
stars
had
no
metals
at
all.
They
had
no
no
heavier
elements
than
hydrogen
and
helium,
and
so
the
metallicity
there
would
be
you
know,
effectively
zero
stuff,
and
so
our
sun
is
the
reference
point.
We
use-
and
we
say
the
sun
has
a
metallicity-
I
mean
technically
it's
it's
a
it's.
B
A
log
base,
10
of
this
ratio
of
of
iron
to
helium.
Excuse
me
iron
to
hydrogen,
and
it's
a
log
base.
10
of
that
ratio.
So
actually
zero
is
our
sun's
metallicity.
Anything
that's
less
than
zero
has
a
lower
percentage
of
metal
elements
in
there.
So
it
turns
out
like
minus
one.
Metallicity
is
one-tenth.
B
B
So
again,
the
idea
is
that
our
galaxy
cannibalized
other
galaxies
nearby,
those
star
streams,
got
swept
into
our
galaxy
and
they're
mostly
settled
into
it
around
the
disc
but
they're
they're
above
and
below
the
plane
of
the
galaxy
more
more
or
less
and
their
orbits
are
not
circular.
The
way
the
thinnest
stars
are
makes
sense.
B
The
galactic
bulge
is
an
ellipsoidal
region,
centered
on
the
galactic
core,
it's
around
two
thousand
light
years
across
and
approximately
twelve
thousand
light
years
thick.
The
bulge
is
filled
with
stars
which
are
both
old
and
they're,
also
metal,
rich,
and
that
seems
like
a
contradiction,
because
old
stars
tend
not
to
be
high
in
metals,
but
it
turns
out
that
it's
thought
the
high
concentration
of
stars
in
the
bulge
results
in
having
many
generations
of
stars
in
a
short
period
of
time.
B
You
see
on
the
screen
and
just
read
that
little
section
for
you,
the
cellular
halo,
is
a
spherical
region
surrounding
the
galactic
core,
with
a
radius
of
approximately
65
000
light
years.
The
halo
contains
only
very
old
population,
two
stars,
so
those
early
stars
were
formed.
They
are
considered
among
the
first
stars
to
have
formed
in
the
galaxy.
B
B
I'm
gonna
stop
there
on
that
one
and
then
go
to
the
final
one,
which
is
the
dark
matter
halo,
so
we've
zoomed
out
yet
again
for
now,
as
you
see
in
the
upper
left,
we're
looking
we're
about
two
eight
hundred
thousand
light
years
away
from
from
before
the
galaxy
here.
Looking
back
at
it,
the
dark
matter,
halo
is
a
vest
vast,
spherical
shell
surrounding
the
galaxy
and
filled
with
dark
matter.
B
This
indicated
that
most
of
the
mass
of
the
galaxy
is
beyond
the
edge
of
the
disk
in
this
spherical
shell,
with
a
radius
of
around
3
000
300
000
light
years,
the
dark
matter
is
believed
to
make
up
about
85
percent
of
the
mass
of
the
universe.
At
this
time
it's
uncertain
what
dark
matter
really
is.
Maybe
brown
dwarfs
white
dwarfs
black
holes
or
some
more
exotic
form
of
matter?
B
B
Do
this,
let's
go
back
here:
orientation,
reset
the
orientation
and
turn
off.
So
you
can
I've
built
these
views
that
you,
the
built-in
views
you
can
construct
all
these
things
yourself
and
then
some.
So
if
you
go
to
visibility
right
now,
I've
got
the
dark
matter,
halo
shown.
If
I
turn
that
one
off
that
disappears
again,
I
can
say:
remove
all
the
deep
sky
objects
that
are
shown
there.
So
now
I'm
kind
of
back
to
a
generic
beginning
view
or
nothing
shown
there.
B
B
B
You
mentioned
you
obtained
the
coordinates
from
somewhere
else
from
somewhere
else,
mostly
so
there's
something
called
the
simbad
database.
I
use
simbad
to
get
most
of
these
coordinates.
It
depends
on
the
object
type.
There
are
certain.
The
galaxies
are
something
called
the
there's,
a
a
catalog
that
some,
a
russian
astronomer
made
for
what's
called
the
local
volume
and
basically
the
local
volume
is
galaxies
out
to
about
33
million
light
years.
B
Although
a
few
galaxies
out
to
like
80,
like
80
million
light
years,
are
in
that
local
volume
also
and
so
I'd
use
the
coordinates
that
he
had
there
for
that
and
but
by
and
large
the
coordinates
come
from
simbad
and
things.
So
did
it
answer
your
question
anything
else
about
that
yeah.
Okay,
impressive,
thank
you.
B
B
B
B
B
I
will
mention.
I
wrote
this.
I
wrote
this
app
using
the
unity
game
engine
to
do
all
the
3d
stuff
and
the
unity
game
engine
doesn't
work
well
on
some
mobile
devices,
at
least
for
the
kind
of
stuff
I'm
trying
to
do
so.
That's
why
it
doesn't
it's.
It's
really
a
desktop
thing
for
the
for
the
browser
based.
B
My
website
it'll
have
details
about
the
app
and
it
will
have
download
links.
Some
of
the
links
go
to
the
app
store,
so,
of
course,
to
download,
for
you
know,
ios
you've
got
to
go
to
the
apple
app
store.
Likewise,
for
the
mac,
it's
on
there,
the
mac
app
store
windows,
it's
on
available
on
the
windows
store,
although
you
can
there,
I
do
have
a
link
there
to
just
download
the
executable
directly.
B
If
you
don't
want
to
deal
with
the
windows
app
store,
which
I
know
some
people
hate
and
there's
a
linux
version
also
and
an
android
version,
so
hopefully
everybody
I
will
mention.
I
originally
wrote
this
app
for
only
for
for
ios
and
mac
os,
so
it's
apple
products
and
I
wrote
that
using
a
very
different
technology
than
the
unity
game
framework
people
liked
it
a
lot
and,
of
course,
where's.
The
windows
version
where's
the
android
version.
B
B
Here
they
were
chained
to
a
wall,
their
heads
were
fixed,
so
they
could
only
look
forward
and
what
they
could
see,
though,
on
the
wall
facing
them,
there
was
light
coming
from
a
fire
over
here
and
all
their
keepers
would
be
moving
around
up
here
and
they
could
see
their
shadows
up
on
this
wall
and
it
was
a
flat
two-dimensional
wall
and
that
became
the
prisoner's
reality.
They
thought
the
world.
B
It's
this
whole
other
thing
I
never
noticed
knew
existed,
and
I
think
this
is
very
apt
for
what
I'm
trying
to
do
with
our
galaxy.
Most
of
us
are
familiar
with.
You
know,
star,
charts
and
where
things
are
in
the
night
sky
and
it's
a
2d
representation,
we
see
it
on
the
celestial
sphere
and
you
say
well:
where
is
it
three
dimensionally
in
the
galaxy
or
around
the
galaxy
and
say
I
don't
know
I've
never
seen
that
before
and
so.
B
B
B
Well,
in
the
same
way,
I
think
it's
really
beneficial,
or
at
least
interesting,
to
know
where
it
is
three-dimensionally,
and
it
really
will
enhance
your
observing,
probably
enhance
your
imaging
just
to
have
this
sense
of
where
these
objects
are.
I
also
find
doing
I
do
a
lot
of
public
outreach.
That's
one
of
my
favorite
aspects
of
the
hobby
actually,
and
I
use
this
app
at
public
outreach
all
the
time
and,
of
course,
people
always
say
well,
how
far
away
is
that
thing?
B
We're
looking
at
and
I'll
tell
them
and
I'll
say:
well,
here's
where
it
actually
is
in
the
galaxy
that
you're
looking
at
and
they're
blown
away.
They
think
it's
just
really
really
cool
to
be
able
to
see
this
representation
of
where
it
is
they're.
Looking
in
the
galaxy,
when
they're
looking
at
a
global
cluster,
an
open
cluster
nebulae
things
like
that
or
some
other
galaxy.
B
And
then
there's
this
question:
why
has
this
been
neglected
for
so
long?
I
don't
fully
understand.
I
don't
understand
what
professional
astronomers
know
I
mean.
Maybe
they
think
about
this
stuff
in
three
dimensions,
all
the
time
or
maybe
not,
but
I
can
guarantee
you
from
talking
to
amateurs
most
amateur
astronomers.
Just
don't
think
this
way,
and
it's
kind
of
a
mystery
to
me
and
again
until
I
read
craig
crossan's
book
that
binocular
astronomy
book.
B
I
didn't
understand
this
stuff
and
yes,
it's
mentioned
in
you
know,
magazine
articles
and
websites
and
things
like
that.
They
might
mention
a
little
bit
about
it,
but
they
really
don't
have
a
good
visualization
tool
to
see
it
and
there
are
a
few
websites
that
that
try
to
do
it,
but
it's
more
of
a
static
kind
of
view.
It's
not
something
you
can
kind
of
pan
around
and
zoom
in
and
out
and
see
it.
B
What
I
consider
be
a
revolutionary
way
of
looking
at
things
doesn't
catch
on
more.
So
you
know,
if
you
guys
use
this
thing
download
it
again.
It's
free
app,
doesn't
cost
you
anything
matter
of
fact.
If
you
go
to
the
our
galaxy.otherwise.com,
you
don't
even
have
to
download
anything.
You
just
go
to
the
website.
You
can
play
with
a
little
bit
if
you
find
it
exciting
and
think
it's
you
know
cool.
I
would
appreciate
it
very
much
if
you
would
spread
the
word.
B
B
B
A
B
B
B
I'm
actually
trained
as
a
zoologist,
I'm
not
a
programmer
by
training.
I've
had
like
one
computer
programming
course,
I'm
kind
of
self-taught,
but
I'm
I'm
actually
interested
in
theoretical
population
dynamics
and
ecosystem
modeling,
and
things
like
that.
That's
how
I
got
my
initial
experience
with
computers
and
things
I
left
academics
to
start
a
software
company.
I
was
up
in
washington
state
in
seattle
at
the
time.
I
then
and
we've
we
founded
a
company.
B
We
wrote
software
for
well,
we
started
writing
a
word
processor
for
macintoshes
and
that
could
just
well
matt
came
out
in
84.
a
couple
years
before
that
apple
approached
us
and
wanted
us
to
write
a
word
processor
for
the
macintosh.
We
actually
right
now.
If
anybody
is
familiar
with
right
now
and
that's
another
app
I've
written
way
back
when
in
the
dark
ages
and
then
when
steve
jobs
got
kicked
out
of
next
computers.
I
was
gonna,
get
kicked
out
of
apple
and
founded
next
computers.
B
They
needed
programmers
and
they
needed
somebody
to
write
a
word
processor
and
they
said
well
how
about
those
guys
up
in
seattle.
They
did
right
now
and
that
worked
out
pretty
well,
and
so
they
actually
bought
our
company
and
hired
us,
and
I
went
down
and
worked
in
the
bay
area
for
about
four
years
working
with
steve
and
stuff
and
worked.
I
was
employed
18
there,
so
you
know
a
fairly
regular
interaction
with
him
and
things
like
that,
and
then
I
decided
to
leave.
B
I
got
tired
of
the
bay
area
and
wanted
to
get
back
up
into
washington
state
and
when
I
was
gonna
form
a
company
up
there.
I
was
looking
around
for
names
and
it's
been
a
long
story
here.
I
just
wanted
to
do
some
software.
That
was
a
little
different.
It
was
not
you
know
the
run-of-the-mill
thing,
and
so
I
thought
well,
let's
call
my
company
otherwise
and
again,
because
I
registered
this
domain
back
in
1990
before
all
the
good
domains
were
snapped
up.
B
B
Sorry
about
that
what
it
is,
I
guess
I
could
consider
open
sourcing
it,
but
I'm
not
sure
that's
what
I
want
to
do.
Thank
you.
I
appreciate
that.
Can
we
contribute
code?
No,
it's
not
open
source.
What's
the
cross-platform
technologies,
I
mentioned
it's.
The
unity
game,
engine
unity,
game
engine
is
something
totally
different
than
what
I
was
familiar
with
before
and
it's
a
totally
different
way
of
writing
apps,
and
so
there
was
definitely
a
learning
curve
for
me
to
do
that.
B
In
reality,
I
actually
started
out
with
a
different
cross-platform
thing
called
xamarin,
but
xamarin
had
so
many
bugs
and
it
was
so
frustrating
I
finally
just
gave
up
on
it.
It's
like.
I
can't
make
this
work
in
xamarin.
That's
why
I
went
over
and
tried
unity
and
unity
actually
works
pretty
well,
but
I'd
say
it's
very
different
than
most
of
the
programming
I've
done.
A
Let
me
ask
one
so
it
seems
like
well.
The
one
thing
that
struck
me
when
you
were
showing
you
know
like
the
stars
was
obviously
like.
You
said,
since
you
were
limited
to
the
you
know,
magnitude,
6
or
whatever
it
was
going
to
be
nearby
stars.
So,
and
you
mentioned
that
you
you
needed
to
limit
the
number
of
stars
for,
for,
I
guess
display
reason,
but
it
seems
like
it's
screaming,
for
you
know
why
not
show
well,
I
could.
B
B
B
A
A
B
There's
definitely
a
I
mean,
there's
a
sampling
problem
that
you
know
if
you
showed
you
know
dimmer
stars
or
further
stars
and
things
there.
I
mean
there's
a
lot
of
stars
that
we
we
we
understand
on
our
neighborhood
of
the
sun
pretty
well,
and
what
the
stars
are
there
as
you
get
further
out.
You
know
in
the
next
spiral
arm
outward,
even
and
maybe
with
the
gaia
data.
It's
it's
changing
for
sure,
but
we
don't
have
nearly
the
a
thorough
sampling
of
the
stars.
B
There
there's
just
stuff,
that's
too
obscured
by
dust
and
and
whatnot
so
that
it
it
kind
of
might
give
a
wrong
impression
again.
You'll
you'll
still
see
this
thing
where
hey
it
still
looks
like
things
are
clustered
around
our
sun
and
that's
only
because
it's
not
because
the
stars
aren't
out
there.
It's
because
they're
so
obscured
that
even
with
gaia,
we
don't
have
good
information
on
them.
I
mean
gaia
does
have
a
lot
more
stars,
but
it's
not
a
uniform
representation.
A
B
Nobody
has
asked
for
it.
It
would
be
a
lot
of
work
too,
and
it
would
also
probably
you
could
probably
run
it
on
desktop
machines
with
a
lot
more
stars
again.
One
of
my
goals
was
to
have
this
run
on
mobile
devices,
so
you
could,
you
know,
carry
it
out
under
the
night
sky
and
use
it
for
outreach
and
things
like
that,
and
there
it's.
I
mean
they're
fast
enough
now,
but
it's
more
memory
each
star,
you
know,
has
a
bunch
of
data
associated
with
it.
B
B
This
is
very
satisfying
my
brain
likes
to
know
where
I
am
and
where
things
are
in
relationship,
I
like
binocular,
viewing
for
3d
effective.
Thank
you
very
much
well.
Thank
you.
Thanks
for
the
presentation,
okay,
all
right!
Well,
I've
enjoyed
talking
to
you
guys.
I
hope
you
I've
at
least
nudged
you
and
excited
you
enough
that
you
might
go,
try
the
app
and
see
what
it
does
again.