The Detectability of Habitable ExomoonsDavid Kipping, Steve Fossey, Giammarco

Campanella

Collaborators: Giovanna Tinetti, Alan Aylward, Ignasi Ribas, Jean-Philippe Beaulieu, Steve Fossey, the HOLMES collaborationc

Critical Questions

Pathways 2009, D. Kipping2/20

• Do extrasolar planets host moons?

Critical Questions

Pathways 2009, D. Kipping2/20

• Do extrasolar planets host moons?• How do moons and planets form?

Critical Questions

Pathways 2009, D. Kipping2/20

• Do extrasolar planets host moons?• How do moons and planets form?• Does complex planetary life require a moon?

Critical Questions

Pathways 2009, D. Kipping2/20

• Do extrasolar planets host moons?• How do moons and planets form?• Does complex planetary life require a moon?• Can moons host life?

How to detect an exomoon

Pathways 2009, D. Kipping2/20

• Highly challenging!• Transit timing variations (Sartoretti & Schneider

1999)• Microlensing (Han et al. 2002)• Planet-moon eclipses (Cabrera & Schneider 2002)• Lightcurve distortions (Simon et al. 2007)• Pulsar timing (Lewis et al. 2008)• Transit duration variations (Kipping 2009)• Rossiter-McClaughlin effect distortions (Simon et al.

2009, poster: Szabo et al.)

Transit timing variations (TTV)

Pathways 2009, D. Kipping2/20

• Planet-moon orbit a common centre-of-gravity• TTV is akin to astrometry

Transit timing variations (TTV)

Pathways 2009, D. Kipping2/20

• Planet-moon orbit a common centre-of-gravity• TTV is akin to astrometry

Transit timing variations (TTV)

Pathways 2009, D. Kipping2/20

• Planet-moon orbit a common centre-of-gravity• TTV is akin to astrometry

Transit timing variations (TTV)

Pathways 2009, D. Kipping2/20

• Planet-moon orbit a common centre-of-gravity• TTV is akin to astrometry

Transit timing variations (TTV)

Pathways 2009, D. Kipping2/20

• A few problems...• Lots of things can cause TTV• TTV frequency > Nyquist frequency => harmonics• TTV amplitude ~ mass*distance

Transit duration variations (TDV)

Pathways 2009, D. Kipping2/20

• TTV is a positional effect, like astrometry• TDV is a velocity effect, like radial velocity

Transit duration variations (TDV)

Pathways 2009, D. Kipping2/20

• TTV is a positional effect, like astrometry• TDV is a velocity effect, like radial velocity

Transit duration variations (TDV)

Pathways 2009, D. Kipping2/20

• TTV is a positional effect, like astrometry• TDV is a velocity effect, like radial velocity

Transit duration variations (TDV)

Pathways 2009, D. Kipping2/20

• TTV is a positional effect, like astrometry• TDV is a velocity effect, like radial velocity

Transit duration variations (TDV)

Pathways 2009, D. Kipping2/20

BENEFITS• TTV and TDV are 90 degrees out-of-phase• TDV amplitude ~ mass/SQRT(distance)• Ratio of amplitudes gives period (distance) and mass• Correlated noise expected to create 180 degree

phase shift• Additional diagnostic – may compare to harmonic

frequencies

Kepler-class photometry

Pathways 2009, D. Kipping2/20

• Kepler is the most precise photometer currently available: 20ppm/hour

• But the ground is catching up fast!• RISE instrument, Liverpool Telescope: 60ppm/hour

Detectability with Kepler

Pathways 2009, D. Kipping2/20

1. Accurately model the noise

Detectability with Kepler

Pathways 2009, D. Kipping2/20

2. Calculate timing and duration uncertainties

Carter et al. (2009) – one of the most useful papers!

Detectability with Kepler

Pathways 2009, D. Kipping2/20

2. Calculate timing and duration uncertainties

Carter et al. (2009) – one of the most useful papers!

Detectability with Kepler

Pathways 2009, D. Kipping2/20

2. Calculate timing and duration uncertainties

Carter et al. (2009) – one of the most useful papers!

Detectability with Kepler

Pathways 2009, D. Kipping2/20

3. Estimate TTV and TDV amplitudes

Kipping et al.(2009a) and (2009b)

Detectability with Kepler

Pathways 2009, D. Kipping2/20

4. Compute SNR for range of planet-moon-star systems with a range of visual magnitudes

• Need to detect both timing signals to 8-sigmas and 3-sigmas

• Period fixed to habitable period• Assume inclination ~ 90 degrees• In each case, planet-moon-star system must be

dynamically stable for 5 Gyr (Barnes & O’Brien 2002)

Results

Pathways 2009, D. Kipping2/20

1) Low-density planets offer largest SNR

Results

Pathways 2009, D. Kipping2/20

2. Habitable moons down to 0.2 Earth masses are detectable

Results

Pathways 2009, D. Kipping

3. Around 25,000 stars could be surveyed for habitable-zone exomoons with Kepler-class photometry