Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Ast

rono

my

210

Sect

ion

1–M

WF

150

0-15

5013

4 A

stro

nom

y B

uild

ing

Thi

s C

lass

(L

ectu

re 2

3):

Gia

nt P

lane

ts

Nex

t Cla

ss:

Deb

ris

Mus

ic: A

my

Hit

the

Atm

osph

ere

–C

ount

ing

Cro

ws

Nig

ht O

bser

vatio

n R

epor

t and

H

W 7

due

on

Fri

day

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Out

line

•Sa

turn

-T

he R

eal L

ord

of th

e R

ings

•U

ranu

s &

Nep

tune

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn, L

ord

of th

e R

ings

•N

amed

for

the

fath

er o

f th

e R

oman

god

s•

Satu

rn is

ver

y si

mila

r to

Jup

iter

–L

arge

pla

net

•M

ostly

liqu

id h

ydro

gen

–H

as a

min

i-so

lar

syst

em•

At l

east

30

moo

ns•

Mos

t are

sm

all

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Equa

toria

l rad

ius

9.45

Ear

thCl

oud-

top

grav

ity0.

93 E

arth

Mas

s95

.2 E

arth

Dis

tanc

e fr

om S

un9.

54 A

UEc

cent

ricity

0.05

6Ti

lt26

.7 °

Year

29.5

Ear

th y

ears

Sola

r da

y 10

hou

rs 1

4 m

inut

es

Leas

t sp

heric

al p

lane

t,

less

den

se (

on a

vera

ge)

than

wat

er.

Ear

th-S

atur

n C

ompa

riso

n

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Equa

toria

l rad

ius

0.84

Jup

iter

Mas

s0.

30 J

upite

rD

ensi

ty0.

52 J

upite

r

Jupi

ter-

Satu

rn C

ompa

riso

n

Alm

ost

as b

ig a

s Ju

pite

r, b

ut

Muc

h le

ss m

assi

ve!

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Mis

sion

s to

Sat

urn

•T

here

hav

e be

en 4

un

man

ned

spac

ecra

ft

mis

sion

s to

Sat

urn

•Pi

onee

r 11

–Fl

yby

1979

•V

oyag

er 1

–Fl

yby

1980

•V

oyag

er 2

–Fl

yby

1981

•C

assi

ni-H

uyge

ns–

Arr

ived

last

yea

r

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Cas

sini

Mis

sion

•L

aunc

hed

on O

ctob

er 1

5th, 1

997

•A

rriv

ed a

t Sat

urn

on J

uly

1st, 2

004

•W

ill o

rbit

Satu

rn f

or 4

yea

rs, m

akin

g fl

ybys

of

the

plan

et, i

ts r

ings

, and

som

e of

its

moo

ns•

Con

tain

s 12

sci

entif

ic in

stru

men

ts•

Als

o ca

rrie

s th

e H

uyge

ns p

robe

, whi

ch w

as

drop

ped

onto

Tita

n, S

atur

n’s

larg

est m

oon,

at t

he

begi

nnin

g of

the

sem

este

r. R

emem

ber?

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Roa

d to

Sat

urn

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Atm

osph

ere

•C

ompo

sitio

n si

mila

r to

Jup

iter

–M

ostly

hyd

roge

n an

d he

lium

•A

tmos

pher

e m

ore

“spr

ead

out”

–L

ess

grav

ity–

Con

tras

t of

clou

d ba

nds

redu

ced

•W

ind

spee

ds f

aste

st a

t the

equ

ator

–10

00 k

m p

er h

our!

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Dri

ving

Sat

urn’

s W

eath

er

•A

s on

Jup

iter,

Sat

urn’

s in

tern

al h

eat d

rive

s w

eath

er–

Satu

rn r

adia

tes

80%

mor

e he

at th

an it

rec

eive

s fr

om th

e Su

n–

Lik

e Ju

pite

r, S

atur

n is

stil

l con

trac

ting!

–A

s is

con

trac

ts, h

eat i

s pr

oduc

ed

•A

s on

Jup

iter,

sto

rms

are

prod

uced

bet

wee

n cl

oud

band

s–

No

long

last

ing

stor

m li

ke th

e G

reat

Red

Spo

t

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Gre

at W

hite

Spo

t

•A

sea

sona

l sto

rm!

–U

nlik

e Ju

pite

r, S

atur

n do

es

have

sea

sons

•A

n am

mon

ia b

ubbl

e th

at

form

s in

the

nort

hern

-he

mis

pher

e su

mm

er–

Las

ts a

few

mon

ths

–G

ets

wra

pped

aro

und

the

plan

et b

y th

e eq

uato

rial

win

ds

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Int

erio

r

•Si

mil

ar s

truc

ture

to

Jupi

ter’

s–

But

Sat

urn

is le

ss m

assi

ve

–T

he in

teri

or is

less

co

mpr

esse

d

•L

iqui

d m

etal

lic h

ydro

gen

crea

tes

a m

agne

tic f

ield

–30

% w

eake

r th

an E

arth

’s

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Rin

gs

•T

wo

mai

n ri

ngs

–Se

vera

l fai

nter

rin

gs

–E

ach

ring

is d

ivid

ed

into

rin

glet

s

•T

he r

ings

are

thi

n–

Onl

y a

few

tens

of

met

ers

thic

k–ra

zor

thin

!

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Vie

w o

f Sa

turn

’s R

ings

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Mak

eup

of th

e R

ings

•T

he r

ings

of

Satu

rn

are

not

solid

rin

gs–

Mad

e of

icy

rock

s

–1c

m to

10m

acr

oss

•N

ew C

assi

nida

ta s

how

s ri

ng p

artic

le s

ize

vari

es

with

dis

tanc

e fr

om S

atur

n–

Not

e th

e ga

p is

fill

ed w

ith

smal

l par

ticle

s

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Gap

s in

the

Rin

gs

•T

here

are

two

prom

inen

t “ga

ps”

in th

e ri

ngs

–C

assi

nidi

visi

on–

Enc

kega

p

•W

hat c

ause

s th

ese

gaps

?•

Cas

sini

divi

sion

–G

ravi

tatio

nal i

nter

actio

ns w

ith M

imas

, a m

oon

of S

atur

n

•E

ncke

gap

–Sw

ept f

ree

by a

sm

all m

oon

in th

e ga

p

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Dir

ty G

ap

•T

he C

assi

niga

p in

Sa

turn

’s r

ings

is

not

com

plet

ely

empt

y•

Con

tain

sri

ngle

ts o

f “d

irty

dus

t”•

Muc

h le

ss r

efle

ctiv

e th

at th

e m

ain

ring

s

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Pro

met

heu

s

Pan

do

ra

Shep

herd

ing

the

Rin

gs

•T

he F

rin

g is

ext

rem

ely

narr

ow

•It

is k

ept t

hat w

ay b

y a

pair

of

moo

ns th

at

flan

k th

e ri

ng

•K

eep

the

ring

par

ticle

s in

line

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

“Spo

kes”

in th

e R

ings

•Sa

turn

’s m

agne

tic

fiel

d ca

n “l

ift”

pa

rtic

les

out o

f th

e ri

ngpl

ane

•D

ecre

ases

ref

lect

ivity

in

par

ts o

f th

e ri

ngs

•C

reat

es a

“sp

oke”

ef

fect

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Why

so

Rin

gy?

•T

ime

to p

lay

mor

e w

ith ti

dal f

orce

s.

•Im

agin

g a

rubb

le p

ile o

f sm

all r

ocks

that

is o

nly

held

toge

ther

by

grav

ity, t

otal

mas

s m

with

ra

dius

r.

•N

ow, p

ut y

our

pile

in th

e gr

avity

fie

ld o

f a

larg

e ob

ject

, mas

s M

and

rad

ius

R a

t a d

ista

nce

d

•W

hen

does

the

tidal

for

ces

pull

it ap

art?

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tot

ally

Tid

al, A

gain

•C

ompe

titio

n of

sel

f-gr

avity

and

out

war

d tid

es

•C

ompa

re f

orce

s on

a te

st p

artic

le a

t sur

face

of

pile

2 r

mm

GF

test

g=

32

d

rM

mG

Fte

stt=

32

2d

rM

mG

r

mm

Gte

stte

st=

33

2r

mMd

=

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tot

ally

Tid

al, A

gain

•C

ompe

titio

n of

sel

f-gr

avity

and

out

war

d tid

es

•C

ompa

re f

orce

s on

a te

st p

artic

le a

t sur

face

of

pile

•If

den

sitie

s ar

e si

mila

r

•T

hen

⇒

33

2r

mMd

=

33

rm

RM≈

33

2Rd

=R

d3.1

=

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Roc

he L

imit

•If

do

a m

ore

deta

iled

anal

ysis

•A

nyth

ing

insi

de th

is li

mit

is to

rn a

part

.

•N

ote

that

the

ring

s ar

e in

side

this

lim

it, w

hile

the

moo

ns a

re o

utsi

de o

f it.

•R

ings

are

cap

ture

d m

oon

or p

roto

-moo

n th

at n

ever

co

ales

ced

Rd

4.2=

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Moo

ns•

Satu

rn h

as a

larg

e nu

mbe

r of

moo

ns–

At l

east

30

•O

nly

Tita

n is

com

para

ble

to J

upite

r’s

Gal

ilean

moo

ns•

Sm

alle

r m

oons

are

mos

tly ic

e, s

ome

rock

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Odd

Moo

ns

•M

imas

-C

rate

r tw

o-th

irds

its

own

radi

us•

Enc

elad

us-

Fres

h ic

e su

rfac

e, w

ater

vol

cano

es?

•H

yper

ion

–Ir

regu

larl

y sh

aped

•Ia

petu

s-

Hal

f its

sur

face

is

10x

dark

er th

an th

e ot

her

half

•P

hoeb

e-

Orb

its S

atur

n ba

ckw

ards

Mimas

Phoebe

Hyperion

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Satu

rn’s

Odd

Moo

ns

Bra

nd n

ew im

ages

fro

m

Mar

ch 9

thE

ncel

adus

has

ate

nuou

s at

mos

pher

e

Phoebe

Hyperion

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tita

n

Tita

n’s

atm

osph

ere

•Sa

turn

’s la

rges

t moo

n–bi

gger

than

Mer

cury

.•

2nd

larg

est m

oon

in th

e so

lar

syst

em a

fter

G

anym

ede.

•O

nly

moo

n to

hav

e a

dens

e at

mos

pher

e–

Den

se n

itrog

en/m

etha

ne a

tmos

pher

e (b

asic

ally

sm

og)

–S

mal

l gre

enho

use

effe

ct–

85%

nitr

ogen

•co

mpo

sitio

n of

anc

ient

Ear

th

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tita

n

Tita

n’s

atm

osph

ere

•A

tmos

pher

ic p

ress

ure

is 1

.5 ti

mes

Ear

th’s

•L

iqui

d/ic

e hy

droc

arbo

ns?

•O

rgan

ic c

ompo

unds

–li

fe?

•Pr

obab

ly n

ot –

too

cold

: 95

K•

May

be

a “d

eep

free

ze”

of th

e ch

emic

al

com

posi

tion

of a

ncie

nt E

arth

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Pie

rcin

g th

e Sm

og

•C

assi

niha

s sp

ecia

l inf

rare

d ca

mer

as to

see

thro

ugh

Tita

n’s

smog

•G

reen

are

as a

re w

ater

ice

•Y

ello

w-o

rang

e ar

eas

are

hydr

ocar

bon

ice

•W

hite

are

a is

a m

etha

ne c

loud

ov

er th

e so

uth

pole

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Cas

sini

-Huy

gens

Huy

gens

Pro

bede

scen

t to

Tita

nJa

n 14

, 200

5

Arr

ival

at S

atur

nJu

ly 1

, 200

4

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Map

ping

Tita

n

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Map

ping

Tita

n

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tita

n•

N2

cam

e fr

om a

mm

onia

(N

H3)

–co

mm

on in

out

er s

olar

sys

tem

•

Seco

nd m

ost a

bund

ant c

ompo

nent

is m

etha

ne (

natu

ral g

as)

-O

ne o

ptio

n is

UV

+ m

etha

ne

hydr

ocar

bons

(e.

g., e

than

e)-

The

n, e

than

e co

nden

ses

and

rain

s do

wn

on T

itan’

s su

rfac

e•

So, i

t mig

ht h

ave

liqui

d et

hane

or

met

hane

lake

s/oc

eans

?•

Man

y or

gani

c co

mpo

unds

sho

uld

be in

atm

osph

ere–

redu

cing

at

mos

pher

e.•

If li

fe e

xist

s he

re, t

hen

it w

ill c

hang

e ou

r w

ater

–cha

uvin

istic

idea

s.

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Dis

cove

ry o

f U

ranu

s

•D

isco

vere

d by

acc

iden

t by

Will

iam

Her

sche

l in

1781

•N

amed

for

the

fath

er o

f Sa

turn

•Fi

rst p

lane

t dis

cove

red

sinc

e an

cien

t tim

es

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Dis

cove

ry o

f N

eptu

ne•

Obs

erva

tions

sho

wed

that

U

ranu

s w

as n

ot o

rbiti

ng th

e w

ay N

ewto

n pr

edic

ted

•T

wo

scie

ntis

ts p

redi

cted

a

new

pla

net,

Nep

tune

–W

ithin

1 d

egre

e of

whe

re it

was

fo

und

in 1

846

•A

triu

mph

of

New

ton’

s L

aws!

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Equa

toria

l rad

ius

4.01

Ear

thCl

oud-

top

grav

ity0.

79 E

arth

Mas

s14

.5 E

arth

Dis

tanc

e fr

om S

un19

.2 A

UTi

lt of

rot

atio

n ax

is98

deg

rees

Year

84 E

arth

yea

rsSo

lar

day

17 h

ours

14

min

utes

(on

its

side

)

Ura

nus-

Ear

th C

ompa

riso

n

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Equa

toria

l rad

ius

3.88

Ear

thCl

oud-

top

grav

ity1.

12 E

arth

Mas

s17

.1 E

arth

Dis

tanc

e fr

om S

un30

.1 A

UTi

lt of

rot

atio

n ax

is29

.6 d

egre

esYe

ar16

4.8

Eart

h ye

ars

Sola

r da

y16

hou

rs 7

min

utes

Nep

tune

-Ear

th C

ompa

riso

n

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Orb

it of

Ura

nus

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

The

Orb

it of

Ura

nus

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Atm

osph

eres

of

Ura

nus

and

Nep

tune

•C

ompo

sed

of a

bout

90%

hyd

roge

n, 9

% h

eliu

m, 1

%

met

hane

and

sm

all a

mou

nts

of a

cety

lene

and

oth

er

hydr

ocar

bons

•T

empe

ratu

res

are

so lo

w, t

hat m

etha

ne ic

e cr

ysta

ls f

orm

cl

ouds

•M

etha

ne a

bsor

bs r

ed li

ght,

mak

ing

the

plan

ets

appe

ar

blui

sh•

The

atm

osph

eres

are

arr

ange

d in

to c

loud

ban

ds r

unni

ng a

t co

nsta

nt la

titud

es–

Sim

ilar

to th

e or

ient

atio

n of

the

clou

d ba

nds

seen

on

Jupi

ter

and

Satu

rn

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Atm

osph

ere

of U

ranu

s

•W

hen

Voy

ager

2 v

isite

d U

ranu

s in

198

6, it

saw

a

feat

urel

ess

pale

blu

e cl

oud

laye

r

•H

igh

cont

rast

im

ages

sho

w

clou

d ba

ndin

g

•W

ind

spee

ds

of 3

50 k

m/h

r

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Stor

ms

on U

ranu

s

•In

the

1990

’s, H

ubbl

e ob

serv

atio

ns o

f U

ranu

s fo

und

stor

ms!

•W

hy n

one

befo

re?

•U

ranu

s’ o

dd s

easo

ns m

ay b

e th

e ca

use

•T

rigg

ered

by

sunl

ight

re

achi

ng a

reg

ion

of th

e pl

anet

for

a f

irst

tim

e in

de

cade

s?

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Stor

ms

on U

ranu

s•

In th

e 19

90’s

, Hub

ble

obse

rvat

ions

of

Ura

nus

foun

d st

orm

s!•

Why

non

e be

fore

?•

Ura

nus’

odd

sea

sons

may

be

the

caus

e•

Tri

gger

ed b

y su

nlig

ht

reac

hing

a r

egio

n of

the

plan

et f

or a

fir

st ti

me

in

deca

des?

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Nep

tune

’s A

tmos

pher

e•

Whe

n vi

site

d by

Voy

ager

2

in 1

989,

Nep

tune

sho

wed

m

ore

feat

ures

than

Ura

nus

•L

arge

sto

rms

–G

reat

Dar

k Sp

ot–

Lik

e th

e G

reat

Red

Spo

t?–

Dis

appe

ared

by

1994

•W

hite

clo

uds

–Fr

ozen

met

hane

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Met

hane

Clo

uds

of N

eptu

ne

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Wat

er W

orld

s

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Mag

netic

Fie

lds

•O

n bo

th U

ranu

s an

d N

eptu

ne–

Com

pres

sed

wat

er m

antle

con

duct

s el

ectr

icity

–R

apid

rot

atio

n (a

bout

17

hour

s)

•G

ener

ates

ver

y od

d m

agne

tic f

ield

s–

Off

-cen

ter

& h

ighl

y til

ted

to th

e pl

anet

s’ s

pin

axes

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Ura

nus’

Rin

gs•

Dis

cove

red

1977

fro

m E

arth

dur

ing

occu

ltatio

n of

a s

tar

•L

ater

obs

erve

d cl

ose-

up b

y V

oyag

er 2

(19

86)

•R

ings

are

dar

k, n

arro

w, d

usty

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Ura

nus’

Rin

gs•

Dis

cove

red

1977

fro

m E

arth

dur

ing

occu

ltatio

n of

a s

tar

•L

ater

obs

erve

d cl

ose-

up b

y V

oyag

er 2

(19

86)

•R

ings

are

dar

k, n

arro

w, d

usty

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Voy

ager

2

Nep

tune

’s R

ings

•T

hin

and

dark

•L

ike

Ura

nus’

ri

ngs

•Se

en b

y V

oyag

er 2

in

198

9

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Nep

tune

’s R

ings

•N

eptu

ne’s

ou

term

ost r

ing

appe

ars

to b

e tw

iste

d!•

Cau

sed

by a

gr

avita

tiona

l in

tera

ctio

n w

ith

one

of it

s m

oons

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Tita

nia

(larg

est)

Mira

nda

(sm

alle

st

of th

e m

ajor

s)

Moo

ns o

f U

ranu

s•

5 in

term

edia

te s

atel

lites

, non

e G

alile

an-s

ized

–T

itani

a, A

riel

, Um

brie

l, O

bero

n, M

iran

da–

Com

pose

d of

50%

roc

k, 5

0% ic

e

•10

min

or o

nes

disc

over

ed b

y V

oyag

er 2

•5

addi

tiona

l min

or o

nes

disc

over

ed s

ince

then

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Moo

ns o

f U

ranu

s

•M

iran

da’s

pat

chw

ork

appe

aran

ce s

ugge

sts

a ca

tast

roph

ic im

pact

•M

iran

da w

as

com

plet

ely

shat

tere

d,

then

rea

ssem

bled

it

self

•D

id a

sim

ilar

impa

ct

flip

Ura

nus

on it

s si

de?

Mar

16,

200

5A

stro

nom

y 21

0 Sp

ring

200

5

Moo

ns o

f N

eptu

ne

•E

ight

moo

ns k

now

n–

2 in

term

edia

te s

ized

, Ner

eid

& P

rote

us

•1

Gal

ilean

-siz

ed, T

rito

n–

Thi

n ni

trog

en a

tmos

pher

e–

50%

roc

k, 5

0% ic

e–

Surf

ace

froz

en

met

hane

/nitr

ogen

–E

vide

nce

of g

eolo

gic

activ

ity (

few

cra

ters

)–

Orb

its N

eptu

ne

back

war

ds