Some Like it Hot: Evidence for the Shrinking Orbit of the 2.2-d Transiting Hot Jupiter Exoplanet HD 189733bTom Santapaga, Edw Guinan, R-L. Ballouz,S.G. Engle, L.E. DeWarf (Villanova Univ.)Stella Kafka (Carnegie Inst, Washington, D.C)

Scale Model for the HD189733 Star- Planet System Showing the interaction of the planet and star’s Magnetic fields. As shown the planet’s orbital motion (~152 km/s) pushes against the magnetic field lines of the star causing the star to spin-up.

Art credit Nick Tripicino

The 8th mag K1.5 V star, HD 189733A shown in the field of the nearby Dumbbell Nebula

A

b

B

a = 0.031 AU (8.75 RK)[3% Distance Earth to Sun]

~220AU (12.2 arcsec)

HD 189733 AK1.5V StarM ~ 0.81 Mʘ

R ~ 0.76 Rʘ

Prot ~ 11.95 dL ~ 0.26 Lʘ

A bHD 189733 bM = 1.13 MJ; R = 1.14 RJ

Porb = 2.22 d; a = 0.031 AUT = 844°C+; (~1550°F)Atm.: H2O, CH4 , (H2O vapor), methane, CO2, sodium

HD 18733 B (12” away from A: 220 AU; P ~3200 yr)M 5V Star/ age ~5-7 Billion yrsR ~ 0.2 Rʘ ; L ~ 10-4 Lʘ

(Bakos et al. 2006)Same Vr

μα μδ as star A

B

Model of the HD 189733 Star/ Planet System

HD 189733 – Selected Properties

HD 189733A(K star)

HD 189733b(Planet)

HD 189733B(M star)

Mass 0.81 M ~1.15 MJ ~0.2 M

Radius 0.76 R ~1.26 RJ ~0.2 Ro

Rotational Period

~11.95 d(tidally locked

2.219 d)Est: >80 d

Orbital Period

- 2.219 d ~3200 yr

Orbital Radius

- 0.031 AU ~220 AU

Age Determinations for the HD 189733 System

METHOD Value AGE REFERENCE

Rotation (dK star ) ~11.95 d ~0.6 Gyr Henry et al. (2007); This study

Ca II HK Emission (dK star)

S(HK) = 0.52

<0.8 GyrCa II HK Emiss. (Moutou et al.

2007 AA, 473.

X-ray Activity (dK star )

~10 Lxx ~0.7 GyrXMM/ Pilletteri et al. (2010);

Age from this study

Lithium Abundance ( dK star )

A (Li) < 0.01

>4 Gyr:Melo, C., (2006), A&A, 460, Age

from Li-depletion

X-ray Activity ( M star )

Log Lx < 26.9

>4.5 GyrXMM-Newton from Pillitteri I.,

( 2010); Age – this study

H-alpha emission ( M star )

EW ~0.0 > 5-6 GyrSpectra from S. Kafka

(Carnegie Cray Telescope)

HD 189733 AK1.5V StarM ~ 0.81 Mʘ

R ~ 0.76 Rʘ

Prot ~ 11.95 dL ~ 0.26 Lʘ

A bHD 189733 bM = 1.13 MJ; R = 1.14 RJ

Porb = 2.22 d; a = 0.031 AUT = 844°C+; (~1550°F)Atm.: H2O, CH4 , (H2O vapor), methane, CO2, sodium

HD 18733 BM 5V StarR ~ 0.2 Rʘ ; L ~ 10-4 Lʘ

(Bakos et al. 2006)Same Vr

μα μδ as star A

B

A

b

B

a = 0.031 AU (8.75 RK)[3% Distance Earth to Sun]

~220AU

Io – Jupiter - A possible Analog for understanding the HD 189733Ab

magnetically Interacting Planet-Star System

HD189733 A & AbHD 189733 A has signifcant chromospheric & coronal X-ray emissions. Also the star has starspots covering ~3% of star’s surface that produce brightness variations of up to 2%. The star’s rotation period (11.95 days) and its resulting magnetic dynamo-generated emissions are similar to dK0-5 stars in the Hyades cluster (age ~ 650 Myr). But the age indicators of the dM5 companion indicate a much older age (>5-6 Gyr).

Artwork from Tinetti: ESA/NASA

The final fate of HD189733b as it reaches its Roche critical surface. This occurs at an orbital period of ~ 6 hr and at an orbital distance of ~2 stellar radii (i.e. at a = 0.007 AU).