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