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“Som
etim
es I
thin
k w
e're
alo
ne. S
omet
imes
I th
ink
we'
re n
ot. I
n ei
ther
cas
e, th
e pr
ospe
ct is
sta
gger
ing!
”A
rthu
r C
. Cla
rke
Wha
t We
Will
Lea
rn T
oday
•H
ow d
o w
e de
tect
pla
nets
aro
und
othe
r st
ars?
•H
ow d
o th
e di
ffere
nt te
chni
ques
w
ork?
•W
hich
tech
niqu
e(s)
hav
e be
en th
e m
ost e
ffect
ive
to-d
ate?
•H
ow w
ill w
e se
arch
for
Ear
th-li
ke
plan
ets?
Pla
nets
Aro
und
Oth
er S
tars
•“E
xtra
-sol
ar p
lane
ts”
or “
Exo
plan
ets”
•T
he C
oper
nica
n re
volu
tion
rais
ed th
e qu
estio
n of
w
heth
er p
lane
ts o
rbit
othe
r st
ars
•B
ut, w
hat i
s a
plan
et?
–T
he IA
U o
nly
defin
ed a
pla
net i
n ou
r S
olar
Sys
tem
–W
e do
not
hav
e a
curr
ent d
efin
ition
of a
pla
net i
n ge
nera
l!
•S
tars
–F
use
Hyd
roge
n in
thei
r co
re d
urin
g th
eir
Mai
n S
eque
nce
phas
e
–A
t lea
st 8
0 M
Jup
•B
row
n D
war
fs–
Fus
e D
eute
rium
or
Lith
ium
in th
eir
core
–A
t lea
st 1
3 M
Jup
•P
lane
ts–
Bel
ow ~
13
MJu
p
–O
rbit
a st
ar
Det
ectin
g E
xopl
anet
s is
Har
d•
If w
e liv
ed o
n a
plan
et a
roun
d a
near
by s
tar,
say
abo
ut
10 li
ght y
ears
aw
ay–
Onl
y 11
kno
wn
star
s ar
e w
ithin
10
lyfr
om th
e S
un
–T
he S
un w
ould
be
visi
ble
to th
e na
ked
eye
as a
sta
r
–E
arth
wou
ld b
e•
0.00
003
arcs
ecin
siz
e–
0.5
mm
pen
cil t
ip h
eld
over
200
0 m
iles
away
!
•0.
3 ar
csec
away
from
the
Sun
–0.
5 m
m p
enci
l tip
hel
d ov
er 2
mile
s aw
ay
•Le
ss th
an a
bill
iont
h as
brig
ht a
s th
e S
un
–Ju
pite
r w
ould
be
•0.
0003
arc
sec
in s
ize
–0.
5 m
m p
enci
l tip
hel
d ov
er 2
00 m
iles
away
!
•1.
5 ar
csec
away
from
the
Sun
•A
bout
a b
illio
nth
as b
right
as
the
Sun
•P
lane
ts a
re v
ery
hard
to s
ee n
ext t
o th
eir
brig
ht s
tars
Dis
cove
ry o
f an
Exo
plan
et•
Ann
ounc
emen
t of e
xopl
anet
disc
over
y–
Oct
ober
6, 1
995
–M
iche
l May
or a
nd D
idie
r Q
uelo
z
–In
depe
nden
tly c
onfir
med
soo
n af
ter
by G
eoffr
ey M
arcy
& P
aul
But
ler
•S
tar:
51
Peg
asi
–50
ligh
t yea
rs a
way
•S
ince
then
, ove
r 20
0 pl
anet
s ha
ve b
een
disc
over
edht
tp://
exop
lane
ts.o
rght
tp://
exop
lane
t.eu
Exo
plan
et D
etec
tion
Tec
hniq
ues
Indi
rect
met
hods
:•
Rad
ial V
eloc
ity•
Tra
nsits
•A
stro
met
ry•
Pul
sar
Tim
ing
•M
icro
lens
ing
Dire
ct m
etho
ds:
•D
irect
imag
ing
The
Clu
e: P
lane
ts M
ake
Sta
rs W
obbl
e
•C
ente
r of
Mas
s –
The
Ear
th g
oes
arou
nd th
e S
un–
The
Moo
n go
es a
roun
d th
e E
arth
•M
ost m
etho
ds in
fer
the
pres
ence
of p
lane
ts b
y de
tect
ing
stel
lar
wob
ble
Ear
th a
roun
d S
un: 3
0 km
/s
Jupi
ter
arou
nd S
un: 1
3 km
/s
Sun
, due
to E
arth
: 0.1
m/s
Sun
, due
to J
upite
r: 1
3 m
/sT
his
can
be d
etec
ted!
Fig
13.
1
The
Clu
e: P
lane
ts M
ake
Sta
rs W
obbl
e
•C
ente
r of
Mas
s –
The
Ear
th g
oes
arou
nd th
e S
un–
The
Moo
n go
es a
roun
d th
e E
arth
•M
ost m
etho
ds in
fer
the
pres
ence
of p
lane
ts b
y de
tect
ing
stel
lar
wob
ble
Ear
th a
roun
d S
un: 3
0 km
/s
Jupi
ter
arou
nd S
un: 1
3 km
/s
Sun
, due
to E
arth
: 0.1
m/s
Sun
, due
to J
upite
r: 1
3 m
/sT
his
can
be d
etec
ted!
Fig
13.
2
Rad
ial V
eloc
ity: T
he D
oppl
er E
ffect
•M
easu
re th
e st
ar’s
vel
ocity
tow
ard
or a
way
fro
m
Ear
th
Fig
13.
3 a
Ste
llar
RV
Lea
ds to
Pla
net I
nfo
Rad
ial V
eloc
ity: S
umm
ary
•S
pect
rosc
opy
is u
sed
to m
easu
re
Dop
pler
shi
fts•
Mos
t pro
duct
ive
met
hod
so fa
r–
95%
of a
ll pl
anet
s de
tect
ed
•A
ll ar
e gi
ant p
lane
ts, d
own
to a
bout
N
eptu
ne’s
mas
ses
•N
eeds
a fa
irly
incl
ined
sys
tem
•R
equi
res
a ve
ry f
ine-
tune
d pr
oces
s to
det
ect p
lane
ts–
Spe
cial
ized
fie
ld (
3 m
/s p
reci
sion
)–
Ded
icat
ed lo
ng-t
erm
sur
veys
•C
an o
nly
obta
in m
inim
um
com
pani
on m
ass
–H
ow m
any
“pla
nets
” ar
e ac
tual
ly
stel
lar
com
pani
ons?
Fig
13.
3 b
Tra
nsits
•R
emem
ber
any
Mer
cury
or
Ven
us tr
ansi
t ev
ents
?•
Pho
tom
etry
is u
sed
to m
easu
re c
hang
e in
ste
llar
brig
htne
ss a
s th
e pl
anet
pas
ses
in fr
ont
Fig
13.
7
Tra
nsits
: Plu
ses
& M
inus
es•
Adv
anta
ges
–C
an g
et lo
ts o
f inf
orm
atio
n•
Rad
ii•
Incl
inat
ion
•E
ccen
tric
ity–
Can
pro
be p
lane
tary
atm
osph
eres
!•
Dis
adva
ntag
es–
Fav
ors
clos
e-in
pla
nets
, or
very
incl
ined
orb
its–
Har
d to
do,
spe
cial
ists
req
uire
d–
Sys
tem
s de
tect
ed c
an b
e fa
r, fo
llow
-up
obse
rvat
ions
di
ffic
ult
•F
utur
e–
NA
SA
’s K
eple
rM
issi
on–
Laun
ch: F
ebru
ary
2009
–W
ill d
etec
t Ear
th-s
ized
pla
nets
!
Fig
13.
8
Ast
rom
etry
•P
reci
se lo
catio
n of
sta
rs•
Det
ect s
tar’s
wob
ble
in p
lane
of s
ky•
Adv
anta
ges:
–
Wor
ks fo
r al
l inc
linat
ions
–C
an g
et a
ll or
bita
l par
amet
ers,
incl
udin
g in
clin
atio
n an
d m
asse
s!
•D
isad
vant
ages
:–
Incr
edib
ly h
ard
to d
o: s
pace
-bas
ed in
terf
erom
etry
–W
orks
wel
l onl
y fo
r ne
arby
sys
tem
s
•F
utur
e–
NA
SA
SIM
Pla
net Q
uest
mis
sion
?–
Few
mic
ro-a
rcse
cond
reso
lutio
n!–
Can
det
ect n
earb
y E
arth
s
Pul
sar
Tim
ing
•P
ulsa
rs a
re tr
uly
incr
edib
le o
bjec
ts–
For
mer
ly h
eavy
wei
ght,
now
dea
d st
ars
–A
tom
s cr
ushe
d by
gra
vita
tiona
l for
ce!
–S
ize
of a
city
, mas
s of
the
Sun
!–
One
teas
poon
ful w
eigh
s a
billi
on to
ns!
–V
ery
stro
ng m
agne
ts 1
014
G, E
arth
’s is
½!
•B
eaco
ns in
to s
pace
•B
est c
lock
s in
the
univ
erse
•P
lane
ts d
etec
ted
by s
mal
l var
iatio
ns in
tim
ing
•F
irst p
lane
ts fo
und
outs
ide
sola
r sy
stem
(19
94)
•P
lane
ts fo
rmed
afte
r st
ar d
ied!
Mic
role
nsin
g
•G
ravi
ty b
ends
ligh
t–
Mad
e E
inst
ein
fam
ous
•A
dvan
tage
–C
an d
etec
t Ear
th-m
ass
plan
ets
•D
isad
vant
ages
–R
equi
res
a ra
re c
hanc
e al
ignm
ent
–N
ot r
epea
tabl
e–
Det
ecte
d pl
anet
s ar
e ty
pica
lly
very
far
•F
ollo
w-u
p ob
serv
atio
ns d
iffic
ult
•O
nly
a fe
w fo
und
so fa
r
Dire
ct Im
agin
g
•V
ery
hard
to d
o•
Fou
r fo
und
so fa
r•
Wor
ks b
est f
or y
oung
, ho
t, m
assi
ve p
lane
ts
arou
nd w
impy
sta
rs•
Luck
y fin
ds v
ersu
s an
or
gani
zed
sear
ch
