It’s Full of Stars! …eeyore.astro.illinois.edu/.../spring05/Lectures/lecture2.pdf · ·...
Transcript of It’s Full of Stars! …eeyore.astro.illinois.edu/.../spring05/Lectures/lecture2.pdf · ·...
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Ast
rono
my
210
Sect
ion
1–M
WF
150
0-15
5013
4 A
stro
nom
y B
uild
ing
Les
lie L
oone
yP
hone
: 24
4-36
15E
mai
l: lw
l w@wui
ucw. w
edu
Off
ice:
Ast
roB
uild
ing
#218
Off
ice
Hou
rs:
MT
F 1
0:30
-11:
30 a
.m.
or b
y ap
poin
tmen
t
http
://e
eyor
e.as
tro.
uiuc
.edu
/~lw
l/cla
sses
/ast
ro21
0/sp
ring
05/
Thi
s C
lass
(L
ectu
re 2
):
The
Nig
ht S
ky
Nex
t Cla
ss:
Ear
ly C
osm
olog
y
Mus
ic: F
ly A
\way
–L
enny
Kra
vitz
Hom
ewor
k #1
due
nex
t Fri
!H
omew
ork
#1 d
ue n
ext F
ri!
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Out
line
•C
onst
ella
tions
•T
he C
eles
tial S
pher
e
•M
otio
ns o
f th
e Sk
y
•Se
ason
s
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
A S
ky F
ull o
f St
ars
On
a cl
ear
nigh
t at a
dar
k si
te (
away
fro
m c
ity
light
s), a
bout
how
man
y st
ars
can
we
see
with
th
e na
ked
eye?
1)A
few
mill
ion
2)A
few
tho
usan
d
3)A
few
hun
dred
4)A
few
hun
dred
tho
usan
d
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
It’s
Ful
l of
Star
s!
http
://co
olco
smos
.ipac
.cal
tech
.edu
/im
age_
galle
ries
/lega
cy/2
m_a
llsky
_sta
rs/
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
A S
ky F
ull o
f St
ars
•T
he a
vera
ge p
erso
n on
a c
lear
nig
ht c
an s
ee
abou
t 30
00 s
tars
–
6000
-800
0 to
tal v
isib
le (
abou
t hal
f ar
e be
low
the
hori
zon)
–A
ll in
our
Gal
axy
and
rela
tivel
y cl
ose
to u
s
•In
late
Jul
y 20
03, t
he t
otal
num
ber
of s
tars
in
the
obse
rvab
le U
nive
rse
was
est
imat
ed t
o be
: –
70 s
extil
lion
(70
thou
sand
mill
ion
mill
ion
mill
ion
or
7×10
22)
–A
bout
10
times
the
num
ber
of g
rain
s of
san
d on
all
of
the
Ear
th’s
bea
ches
and
des
erts
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Bul
l, m
an,
hipp
opot
amus
,cr
ocod
ile(A
ncie
nt E
gypt
)
Tai
l of a
bea
r(A
ncie
nt G
reek
s an
dN
ativ
e A
mer
ican
s)
Cel
estia
l Bur
eauc
rat
(Chi
na)
Plo
w(E
ngla
nd)
Big
Dip
per
(Mod
ern
Nor
th A
mer
ica)
Con
stel
latio
ns
•C
onst
ella
tion
s--
a vi
sual
grou
ping
of
star
s–
nam
ed a
fter
god
s, h
eroe
s, a
nd a
nim
als
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Con
stel
latio
ns &
Ast
eris
ms
•T
oday
we
have
88
“off
icia
l” c
onst
ella
tions
–50
anc
ient
, 38
mod
ern
–E
very
reg
ion
of th
e sk
y “b
elon
gs”
to a
n of
fici
al
cons
tella
tion
•C
omm
only
rec
ogni
zed,
but
“un
offi
cial
” pa
ttern
s ar
e ca
lled
aste
rism
s–
Part
s of
con
stel
latio
ns•
Big
Dip
per,
Gre
at S
quar
e, e
tc..
–C
ross
-con
stel
latio
n
pa
ttern
s•
The
Sum
mer
Tri
angl
e, e
tc..
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Zod
iac
•T
he m
ost f
amou
s of
anc
ient
con
stel
latio
ns–
Ori
gins
dee
p in
our
agr
icul
tura
l pas
t–
Man
y co
nste
llatio
ns s
ymbo
lize
plan
ting
or h
arve
stin
g–
12 c
onst
ella
tions
(so
rt o
f), o
ne f
or e
ach
luna
r cy
cle
per
year
.
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Rea
l Zod
iac
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Lio
ns, V
irgi
ns, a
nd B
ears
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Ang
ular
Siz
es o
n th
e Sk
y
•D
iam
eter
of
Sun
or M
oon
roug
hly
half
a d
egre
e
•Ju
pite
r is
abo
ut 4
5 ar
csec
onds
•Ear
th r
otat
es a
t 36
0 de
gree
s/24
hou
rs o
r15
deg
rees
per
hou
r
•1 a
rcse
cond
is th
e an
gula
r si
ze o
f a
dim
e fr
om a
bout
2.
5 m
iles
away
2.5
mile
s!
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Sum
mer
Tri
angl
e
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Cla
sh o
f th
e T
itans
(F
all S
ky)
•T
he f
all s
ky te
lls
the
tale
of
And
rom
eda
and
Pers
eus
•A
n en
tire
Gre
ek
myt
h in
the
sky!
•A
lso
a m
ajor
m
otio
n pi
ctur
e!
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Star
Nam
es
•M
any
brig
ht s
tars
hav
e pr
oper
nam
es•
Exa
mpl
es–
Siri
us –
from
Gre
ek f
or
“sco
rchi
ng”
–B
etel
geus
e –
from
Ara
bic
for
“the
arm
pit o
f th
e ce
ntra
l one
”
The
win
ter
tria
ngle
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Con
stel
latio
ns A
re P
atte
rns
•R
emem
ber,
the
cons
tella
tions
are
pa
tter
ns–
Usu
ally
not
phy
sica
lly
asso
ciat
ed–
Star
s in
a c
onst
ella
tion
can
be
very
far
away
fr
om e
ach
othe
r
•T
he s
ky w
ould
look
ve
ry d
iffe
rent
fro
m
anot
her
sola
r sy
stem
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Dat
a•
Loo
k at
the
Star
s.
•W
hat a
re th
e D
ata?
–D
iurn
al m
otio
ns
–Se
ason
al m
otio
ns
•H
ow c
an w
e us
e th
ose
to m
ake
a m
odel
of
wha
t we
can
see
with
na
ked
eye
astr
onom
y?
http
://w
ww
.ex-
astr
is-s
cien
tia.
org/
galle
ry/s
tmag
azin
e/da
ta-q
ueen
-kis
s.jp
g
http
://a
trop
os.a
s.ar
izon
a.ed
u/ai
z/te
achi
ng/a
250/
lect
ure1
.htm
l
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Ter
min
ator
6:00
AM
6:00
PM
Noo
nM
idni
ght
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Pol
aris
, the
Pol
e St
ar
•Po
lari
s is
a s
tar
that
appe
ars
very
clo
se
to th
e N
orth
C
eles
tial P
ole
(NC
P)
•If
you
fin
d Po
lari
s,
you
know
Nor
th.
•V
ery
usef
ul f
or o
cean
na
viga
tion
•Is
it th
e br
ight
est s
tar
in th
e Sk
y?
Pola
ris
⊗N
CP
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Pola
ris
Que
stio
n
If w
e to
ok a
tim
e-la
pse
phot
o of
the
sta
rry
nigh
t sk
y to
war
d P
olar
is, w
hat
wou
ld it
look
like
?
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Dai
ly P
aths
•E
arth
’s r
otat
ion
crea
tes
daily
(d
irun
al)
mot
ion
of
the
star
s, S
un, M
oon,
&
pla
nets
•
Ear
th s
pins
eas
twar
d,
so s
tars
app
ear
to
mov
e w
estw
ard
–da
ily p
aths
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Cel
estia
l Sph
ere
Imag
ine
the
Sun,
M
oon,
& s
tars
on
a tr
ansp
aren
t gl
obe
arou
nd th
e E
arth
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Seas
onal
Mot
ion
•A
s th
e E
arth
orb
its th
e Su
n, th
e st
ars
visi
ble
at
nigh
t cha
nge–
The
con
stel
latio
ns a
re d
iffe
rent
in
ever
y se
ason
.
•A
sta
r cr
osse
s th
e m
erid
ian
one
hour
ear
lier
ever
y tw
o w
eeks
.
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Cel
estia
l Pol
es a
nd E
quat
or
•C
eles
tial
pol
es–
exte
nsio
ns o
f th
e E
arth
's a
xis
onto
th
e ce
lest
ial
sphe
re
•C
eles
tial
equ
ator
–pr
ojec
t the
Ear
th's
eq
uato
r on
to th
e ce
lest
ial s
pher
e
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
You
r V
iew
of
the
Sky
•Z
enit
h–
poin
t di
rect
ly o
verh
ead
•H
oriz
on–
mar
ks
the
inte
rsec
tion
of E
arth
and
sky
•M
erid
ian
–fr
om
Nor
th to
Sou
th th
roug
h th
e ze
nith
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Cel
estia
l Coo
rdin
ates
•M
easu
ring
Nor
th-S
outh
–E
arth
:L
atitu
de, m
easu
res
from
the
equa
tor
–Sk
y:D
eclin
atio
n, m
easu
res
from
the
cele
stia
l eq
uato
r
•M
easu
ring
Eas
t-W
est
–E
arth
:L
ongi
tude
, mea
sure
d fr
om G
reen
wic
h,
Eng
land
–Sk
y:R
ight
Asc
ensi
on, m
easu
red
from
the
Ver
nal E
quin
ox (
posi
tion
of th
e Su
n on
fir
st d
ay
of S
prin
g)
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Mot
ions
in th
e Sk
y
Celestial E
quator
To N
orth
Cel
estia
l Pol
e
Ang
le =
Lat
itude
NW
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Cha
nges
with
Lat
itude
•T
he p
ositi
ons
of th
e ce
lest
ial p
oles
and
cele
stia
l equ
ator
on th
e sk
y de
pend
on y
our
latit
ude
•N
ote:
The
cel
estia
l eq
uato
r al
way
s cr
osse
s th
e ho
rizo
n at
due
eas
t and
du
e w
est
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Que
stio
n
You
obs
erve
a s
tar
risi
ng d
irec
tly to
the
east
. W
hen
this
sta
r re
ache
s its
hig
hest
po
sitio
n ab
ove
the
hori
zon,
whe
re w
ill it
be
?a)
Hig
h in
the
nort
hern
sky
b)H
igh
in th
e ea
ster
n sk
yc)
Hig
h in
the
sout
hern
sky
d)H
igh
in th
e w
este
rn s
kye)
Dir
ectly
ove
rhea
d
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Cir
cum
pola
r St
ars
•T
he s
ky a
ppea
rs to
spi
n ar
ound
Po
lari
s.•
Ear
th’s
rot
atio
n is
cou
nter
cl
ockw
ise,
if y
ou w
ere
to lo
ok
dow
n on
the
Nor
th P
ole
•M
ost s
tars
’ da
ily p
aths
ris
e in
th
e ea
st a
nd s
et in
the
wes
t•
But
, som
e ar
e so
clo
se to
Po
lari
s, th
ey c
an’t
rea
ch th
e ho
rizo
n!•
Cal
led
circ
umpo
lar
star
s
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
At t
he N
orth
Pol
e
•Po
lari
s is
dir
ectly
over
head
•T
he s
ky a
ppea
rsto
spi
n ar
ound
it
•St
ars
don’
t ris
e or
set
, the
y ju
st
go a
roun
d
•A
ll st
ars
are
circ
umpo
lar
at th
e po
le!
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
At t
he E
quat
or
•Po
lari
s is
rig
ht
on th
e ho
rizo
n
•St
ars
rise
str
aigh
t up
fro
m th
e ea
ster
n ho
rizo
n an
d se
t str
aigh
t do
wn
on th
e w
este
rn h
oriz
on
•N
o st
ars
are
circ
umpo
lar
at th
e eq
uato
r!
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Sout
h of
the
Equ
ator
http
://w
ww
.dan
hell
er.c
om/i
mag
es/A
fric
a/T
anza
nia
/Kili
man
jaro
/Mou
ntai
n/Sl
ides
how
/im
g15.
htm
l
•So
uth
of th
e eq
uato
r,
you
can'
t see
Pol
aris
•Y
ou d
o se
e th
e So
uth
Cel
estia
l Pol
e
SCP
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Fre
e T
rip
Aro
und
the
Sun
•T
he E
arth
orb
its th
e Su
n ev
ery
365
days
•T
he p
lane
of
the
Ear
th’s
orb
it is
cal
led
the
eclip
tic
“Liv
ing
on E
arth
may
be
expe
nsiv
e, b
ut it
incl
udes
an
annu
al f
ree
trip
aro
und
the
sun.
”-A
slei
ghB
rilli
ant
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Ecl
iptic
on
the
Cel
estia
l Sp
here
•T
he e
clip
tic c
an a
lso
be d
raw
n on
the
cele
stia
l sph
ere
•N
ote,
the
eclip
tic a
nd
the
cele
stia
l equ
ator
ar
e no
t the
sam
e ci
rcle
s
•T
he E
arth
’s a
xis
is
tilte
d to
the
eclip
tic
plan
e by
23.
5º
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Sun
Mov
es in
the
Sky
http
://pl
anck
.phy
s.uw
osh.
edu/
mik
e/ex
erci
ses/
anim
/ecl
iptic
_mov
ie.m
ov
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
The
Gre
gori
an C
alen
dar
•A
ctua
lly, t
he r
evol
utio
n pe
riod
is
365
.242
2...
days
long
•A
reg
ular
cal
enda
r ye
ar is
365
da
ys lo
ng
•A
ccou
ntin
g fo
r di
ffer
ence
–L
eap
year
s: 1
ext
ra d
ay
ev
ery
4 ye
ars
= 3
65.2
5 da
ys
–N
o le
ap y
ears
ever
y 10
0 ye
ars
= 3
65.2
4 da
ys
–A
dd le
ap y
ear
ever
y 40
0 ye
ars
= 3
65.2
425
days
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Bui
ldin
g A
Cel
estia
l Sph
ere
•N
CP
is u
p fr
om h
oriz
on a
t an
ang
le e
qual
to
you
r la
titud
e•
Equ
ator
is 9
0o
from
NC
P•
Ecl
iptic
is
23.5
otil
ted
from
equ
ator
Zen
ith
Nad
ir
Hor
izonM
erid
ian
No
rth
Cel
esti
alP
ole
So
uth
Cel
esti
alP
ole
Latit
ude
Eq
uat
or Ecl
ipti
c
23
.5o
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Wha
t Cau
ses
the
Seas
ons?
The
Ear
th is
clo
ser
to
the
Sun
in th
e su
mm
er?
•N
o!•
Whi
leth
e E
arth
’s o
rbit
is n
ot p
erfe
ctly
cir
cula
r,
it is
act
ually
clo
sest
to
the
Sun
in J
anua
ry•
Als
o, s
umm
er in
Nor
ther
n H
emis
pher
e is
win
ter
in
Sout
hern
and
vic
e ve
rsa
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Wha
t Cau
ses
the
Seas
ons?
So w
hat d
oes
caus
e th
e se
ason
s?
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Sun'
s D
aily
Pat
hs•
In th
e su
mm
er, t
he
Sun
is n
orth
of
the
cele
stia
l equ
ator
–L
ong
days
–H
igh
in th
e sk
y
•In
the
win
ter,
it is
so
uth
of th
e ce
lest
ial
equa
tor
–Sh
ort d
ays
–L
ow in
the
sky
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Sum
mer
vs.
Win
ter
Sun
ligh
tC
once
ntr
ated
Sun
ligh
tSp
read
Ou
t
Jan
21, 2
005
Ast
rono
my
210
Spri
ng 2
005
Sunl
ight
Spr
ead
Out
_
Sunl
ight
Con
cent
rate
d-
Sunl
ight
Spr
ead
Out
Sunl
ight
Con
cent
rate
d
Seas
ons
Aro
und
the
Wor
ld
Nor
ther
n W
inte
r
Sout
hern
Sum
mer
Sout
hern
Win
ter
Nor
ther
n Su
mm
er