Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small as that of Earth. "Timing variation" asks whether the transit occurs with strict periodicity or if there's a variation.
The first significant detection of a non-transiting planet using transit-timing variations was carried out with NASA's Kepler telescope. The transiting planet Kepler-19b shows transit-timing variation with an amplitude of 5 minutes and a period of about 300 days, indicating the presence of a second planet, Kepler-19c, which has a period that is a near-rational multiple of the period of the transiting planet.
- Miralda-Escude (2001). "Orbital perturbations on transiting planets: A possible method to measure stellar quadrupoles and to detect Earth-mass planets". The Astrophysical Journal 564 (2): 1019. arXiv:astro-ph/0104034. Bibcode:2002ApJ...564.1019M. doi:10.1086/324279.
- Holman; Murray (2004). "The Use of Transit Timing to Detect Extrasolar Planets with Masses as Small as Earth". Science :-,2005 307 (1291). arXiv:astro-ph/0412028. doi:10.1106/science.1107822.
- Agol; Sari; Steffen; Clarkson (2004). "On detecting terrestrial planets with timing of giant planet transits". Monthly Notices of the Royal Astronomical Society 359 (2): 567–579. arXiv:astro-ph/0412032. Bibcode:2005MNRAS.359..567A. doi:10.1111/j.1365-2966.2005.08922.x.
- Invisible World Discovered, NASA Kepler News, 8 September 2011
- Sarah Ballard; Daniel Fabrycky; Francois Fressin; David Charbonneau; Jean-Michel Desert; Guillermo Torres; Geoffrey Marcy; Burke; Howard Isaacson; et al. (2011). "The Kepler-19 System: A Transiting 2.2 R_Earth Planet and a Second Planet Detected via Transit Timing Variations". arXiv:1109.1561 [astro-ph.EP].
- Planet found tugging on transits, Astronomy Now, 9 July 2010
- G.Maciejewski; D.Dimitrov; R.Neuhaeuser; A.Niedzielski; St.Raetz; Ch.Ginski; Ch.Adam, C.Marka; M.Moualla; M.Mugrauer (2010). "Transit timing variation in exoplanet WASP-3b". arXiv:1006.1348v1 [astro-ph.EP].
- M Montalto; et al. (Nov 2, 2012). "A new analysis of the WASP-3 system: no evidence for an additional companion". MNRAS. arXiv:1211.0218. Bibcode:2012MNRAS.427.2757M. doi:10.1111/j.1365-2966.2012.21926.x.
- The Transit Timing Variation (TTV) Planet-finding Technique Begins to Flower