Transcript Detection of Extrasolar Giant Planets

Detection of Extrasolar Giant Planets
Hwihyun Kim
03/30/06
PAPER
• G. W. Marcy & R. P. Butler, “Detection of
Extrasolar Giant Planets”, ARAA, 1998,
36:57-97
HISTORY OF DETECTION
• 4th century : Aristotle and Epicurus argued
about the uniqueness of the Earth
• Late 1500s : Copernicus(con), G. Bruno(pro)
• Early-1900s :
– some “spiral nebulae” such as M51 misinterpreted as
planetary systems
– Jeans-Jeffreys’ model for planet formation
– Aitken(1938) : direct detection or by the wobble
HISTORY OF DETECTION
• Wolszczan & Frail (1992) : 1st planetary system,
PSR1257+12 (post-SN recapture of material) by pulsartiming method
• Mayor & Queloz (1995) : 51 Pegasi by Doppler
periodicity
• Butler & Marcy (1996) : 1st detections of Jupiter-mass
planets to solar-type star, 47 UMa and 70 Vir
• 2000s : HST-NICMOS, Spitzer, Kepler Space
Mission(2007 ?), Space Interferometry Mission(SIM),
Terrestrial Planet Finder(TPF) and so on....
DETECTION TECHNIQUES
• Direct Detections
• Astrometric Detections
• Photometric Technique
• Doppler Technique
• Pulsar Timing
• Gravitational Microlensing
DIRECT DETECTIONS
• Direct Imaging
– Small fluxes from the planets
– Competing wings of the stellar PSF
• Solar-type star with MJ-planet at 5AU
(Benchmark model)
– Visible : ~10-9 (Vs = 5 and Vp = 27, 0.5”)
– IR : improved to ~10-4 but low-resolution(>1”)
• Noise in PSF wings : seeing, microroughness of
the mirror, and diffraction
DIRECT DETECTIONS
• Minimum aperture D (diffraction alone)
 d 5 AU
D  0.4
meters
1 10 pc r
D:aperture, λ:wavelength used, d:distance,
r:orbital separation
• Remedy
– Adaptive optics, Dark-speckle camera(JWST ?)
– Ground-based interferometry, Keck, VLT, Spitzer....
ASTROMETRIC DETECTIONS
• Stellar (proper) motion by its companion
– Determine Mp and i of a planet
– Detect sub-MJ planets with future precision below 0.1 milliarcsec
(mas)
– Confirm planets detected by other means
• Angular wobble
– Proportional to Mp and r
– Inversely proportional to d
• Benchmark model : 0.5 mas
• Palomar 5-m (~250 μas, 1997), Keck (20 μas), & SIM (4 μas)
PHOTOMETRIC TECHNIQUE
• Transit method : reduction in light
– aligned from astronomers’ vantage point
a
tan i 
R*
i:inclination, a:semi-major axis, R *:stellar radius
– 1% dimming by the Jupiter size planet
– Probability :
P(i '  90  i)  cos i '
PHOTOMETRIC TECHNIQUE
• Marcy & Butler(1997) : 0.19% of solar-type
star exhibit transits
• Determination of
– existence rate
– occurrence rate
– Planet radius
DOPPLER TECHNIQUE
• Our Sun
– wobbles around the barycenter with ~13m/s
by Jupiter(12.5 m/s) and Saturn(2.7m/s)
• Semi-amplitude K of the stellar radial
velocity
1/ 3
 2 G 
K 

p


m p sin i
1
(M *  m p )2 / 3 1  e2
2 3
4

a
2
p 
G(M *  mp )
(Kepler's third law)
DOPPLER TECHNIQUE
• Detectability of companions
by the reflex velocity
• Intrinsic velocity scatter(σ) vs.
rotational period(P) for F(∆),
G(⊙) and K(■) dwarfs (Saar
et al, 1997)
OBSERVATIONS OF
EXTRASOLAR PLANETS
• Walker et al (1995) : 21 dwarfs for 12 yrs with
13m/s
• Mayor & Queloz (1995) : 140 MS stars for 3 yrs
• Cochran & Hatzes (1994) : 33 stars for 10 yrs
• Marcy & Butler (1997) : 107 FGKM dwarfs with
~10m/s (8yrs) and 3m/s (4yrs)
DISTRIBUTION OF PLANETARY
MASSES
• Histogram of M sini
for all companions
known around solartype stars
• Tallest peak is at the
lowest, least
detectable masses(010 MJ)
47 Ursae Majoris
• By Butler & Marcy (1996) with Doppler measurement
• P = 3.0 yrs, e = 0.09 ± 0.04, a = 2.1 ± 0.1 AU and
companion mass = (2.4 ± 0.1)/sini
55 Cancri and ρ Corona Borealis
• Mp ~ 1.0 MJ/sini (true masses < 3MJ)
• Orbital radii : 0.11 AU (55 Cnc) and 0.24 AU (ρ
CrB) placing them inward of the icecondensation point (~3AU)
• Low eccentricities (e= 0.04 and 0.11)
– ρ CrB : too large orbit for tidal effects to cause low-e
– 55 Cnc : tidal circulation and period of 14.7 days
• a) 55 Cnc
• b) ρ CrB by
Noyes et al
(1997)
• Both appear to
have MJcompanions in
nearly circular
orbits.
70 Vir & 16 Cygni B : nonsinusoidal velocities
• Very eccentric Keplerian curves
– e = 0.4 (70 Vir) and 0.687 (16 Cygni B)
– Well fit by a simple Keplerian model
70 Vir ( Mp = 6.7 MJ/sini )
16 Cygni - Lick(∆) & McDonald(x)
- Mp = 1.67 ± 0.1 MJ/sini
GIANTS PLANETS ORBITING
WITHIN 0.1AU
• MJ-companions with the orbital
radii <0.1 AU
• Proximity to the star enhances
the detectability (Fig. 1)
• 51 Peg : active corona and high
X-ray flux
• Tau Boo : higher mass
companion (3.7 MJ/sini )
• Upsilon And : short-term
scatter (25m/s) by the rapid
rotation of the star
SUMMARY
• 8 extrasolar planet candidates have been
identified by Keplerian Doppler
shifts(1998).
• Masses are between 0.5-7 MJ and semimajor axes are less than 2.1 AU.
• Detections imply that ~6% of solar-type
stars have giant planets within 2 AU.