The Search for Exomoons David Kipping UCL th

The Search for Exomoons David Kipping, UCL th 23 September 2008 Acknowledgements: Giovanna Tinetti, Alan Aylward, Ignasi Ribas, Jean-Philippe Beaulieu, Steve Fossey, the HOLMES collaboration

Motivation Detection Methods The TDV Effect What is an Exomoon? • A smaller, natural satellite that orbits an extrasolar planet. 2/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect What is an Exomoon? • A smaller, natural satellite that orbits an extrasolar planet. • There are no known exomoons, but their existence is theorized around many exoplanets. 2/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect What is an Exomoon? • A smaller, natural satellite that orbits an extrasolar planet. • There are no known exomoons, but their existence is theorized around many exoplanets. 2/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 3/18 Molecules 2008, D. Kipping

Motivation Current Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. Sartoretti & Schneider 1999 Szabo et al. 2006 Simon et al. 2007 Kipping 2008 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 2. Exomoons are likely to be < MEARTH and rocky. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 2. Exomoons are likely to be < MEARTH and rocky. Belbruno & Gott 2005 Valencia et al. 2006 Canup & Ward 2007 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 2. Exomoons are likely to be < MEARTH and rocky. 3. Complex life may not form on exoplanets without large moons. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 2. Exomoons are likely to be < MEARTH and rocky. 3. Complex life may not form on exoplanets without large moons. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection and proof of principle. 2. Exomoons are likely to be < MEARTH and rocky. 3. Complex life may not form on exoplanets without large moons. Laskar et al. 1993 Ward & Brownlee 2000 Waltham 2004 Lathe 2005 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection. 2. Exomoons are likely to be < MEARTH. 3. Complex life may not form on exoplanets without large moons. 4. There may be more habitable exomoons than exoplanets. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection. 2. Exomoons are likely to be < MEARTH. 3. Complex life may not form on exoplanets without large moons. 4. There may be more habitable exomoons than exoplanets. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection. 2. Exomoons are likely to be < MEARTH. 3. Complex life may not form on exoplanets without large moons. 4. There may be more habitable exomoons than exoplanets. Scharf 2008 3/18 Thommes et al. 2008 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Why Look for Exomoons? 1. A novel detection. 2. Exomoons are likely to be < MEARTH. 3. Complex life may not form on exoplanets without large moons. 4. There may be more habitable exomoons than exoplanets. 5. Implications for planetary formation theory. 3/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Direct Imaging? • • • 4/18 Brightness ratio 1: 1010. An Earth-sized body 0. 02 micro arcseconds. Current interferometric precision 25 micro arcseconds (Baines et al. 2007) Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Direct Imaging? • • • Brightness ratio 1: 1010. An Earth-sized body 0. 02 micro arcseconds. Current interferometric precision 25 micro arcseconds (Baines et al. 2007) NWO Proposal 4/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Direct Imaging? • • Brightness ratio 1: 1010. An Earth-sized body 0. 02 micro arcseconds. Current interferometric precision 25 micro arcseconds (Baines et al. 2007) => Directly imaging an exomoon is currently impossible. NWO Proposal 4/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Radial Velocity? • • 5/18 Radial velocity (Doppler spectroscopy) measures the wobble of the host star due to a planet. This method would be insensitive to a planet + moon system. Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Radial Velocity? • • 5/18 Radial velocity (Doppler spectroscopy) measures the wobble of the host star due to a planet. This method would be insensitive to a planet + moon system. Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Radial Velocity? • • • 5/18 Radial velocity (Doppler spectroscopy) measures the wobble of the host star due to a planet. This method would be insensitive to a planet + moon system. => Radial velocity cannot be used to detect exomoons. Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Occultation? • 6/18 Could we look for the dip in star light due to an exomoon’s shadow? Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect The Transit Method 7/18 Winn et al. 2008 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Occultation? • Planet transit + Exomoon transit Simon et al. 2007 8/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Occultation? • • Problem 1: Transit of moon is very small. Require space-based telescope to do 2. 5 MEARTH. Ballard et al. 2008 8/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Occultation? • Problem 2: Average position of moon results in lightcurves overlapping: indistinguishable. Cabrera & Schneider 2005 8/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Occultation? • • 9/18 Could we look for the dip in star light due to an exomoon’s shadow? => Possible, but somewhat insensitive to low mass objects. Molecules 2008, D. Kipping

Motivation 10/18 Detection Methods The TDV Effect Molecules 2008, D. Kipping

Motivation 11/18 Detection Methods The TDV Effect Molecules 2008, D. Kipping

Motivation 12/18 Detection Methods The TDV Effect Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Time Variation (TTV) 13/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Time Variation (TTV) 13/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Time Variation (TTV) 13/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Time Variation (TTV) 13/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect The Problem with TTV • • 14/18 Lots of things can cause TTV, not just exomoons. Prof. Holman called this the ‘inverse-problem’. Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect The Problem with TTV • • 14/18 Lots of things can cause TTV, not just exomoons. Prof. Holman called this the ‘inverse-problem’. TTV MMOON a. MOON 1 measureable, 2 unknowns => Can’t solve! Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect The Transit Method (7/18) Molecules 2008, D. Kipping

Motivation (12/18) Detection Methods The TDV Effect Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Duration Variation (TDV) 15/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Duration Variation (TDV) 15/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Transit Duration Variation (TDV) 15/18 Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect TTV + TDV = A Unique Signature • • • 16/18 The TDV signals lags behind the TTV signal by 90 o. TTV TDV 1 -10 seconds. TTV and TDV allow you to solve for both the mass and orbital radius of the exomoon. Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect Sensitivity • 17/18 An Earth mass exomoon is detectable from the ground with current instruments! Molecules 2008, D. Kipping

Motivation Detection Methods The TDV Effect The Holy Grail of Exomoons • • • 18/18 Consider a Neptune –like planet around an M-dwarf on a 35 -day period => Goldilocks zone. Consider an Earth mass exomoon orbiting this planet. TTV 140 s and TDV 60 s. Typical TTV error 10 s Typical TDV error 20 s. => Very secure detection of a habitable Earth-like body! Molecules 2008, D. Kipping