Exoplanet detection method using transit timing variations
Animation showing difference between planet transit timing of 1-planet and 2-planet systems. Credit: NASA/Kepler Mission.
Transit-timing variation is a method for detectingexoplanets by observing variations in the timing of atransit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small asthat of Earth. In tightly packed planetary systems, the gravitational pull of the planets among themselves causes one planet to accelerate and another planet to decelerate along its orbit. The acceleration causes the orbital period of each planet to change. Detecting this effect by measuring the change is known as transit-timing variations.[1][2][3][4][5][6][7] "Timing variation" asks whether the transit occurs with strict periodicity or if there exists a variation.
The first significant detection of a non-transiting planet using transit-timing variations was carried out with NASA'sKepler telescope. The transiting planetKepler-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.[8][9]
In 2010, researchers proposed a second planet orbitingWASP-3 based on transit-timing variation,[10][11] but this proposal was debunked in 2012.[12]
Transit-timing variation was first convincingly detected for planetsKepler-9b andKepler-9c[13] and gained popularity by 2012 for confirming exoplanet discoveries.[14]
TTV can also be used to indirectly measure the mass of the exoplanets in compact, multiple-planet systems and/or system whose planets are in resonant chains. By performing a series of analytical (TTVFaster[15]) and numerical (TTVFast[16] and Mercury[17]) n-body integrations of a system of six gravitationally interacting, co-planar planets, the initial mass estimates for the six inner planets ofTRAPPIST-1, along with their orbital eccentricities, were determined.[18]
^Ballard, S.; Fabrycky, D.; Fressin, F.; Charbonneau, D.; Desert, J.-M.; Torres, G.; Marcy, G.; Burke, C. J.; Isaacson, H.; Henze, C.; Steffen, J. H.; Ciardi, D. R.; Howell, S. B.; Cochran, W. D.; Endl, M.; Bryson, S. T.; Rowe, J. F.; Holman, M. J.; Lissauer, J. J.; Jenkins, J. M.; Still, M.; Ford, E. B.; Christiansen, J. L.; Middour, C. K.; Haas, M. R.; Li, J.; Hall, J. R.; McCauliff, S.; Batalha, N. M.; Koch, D. G.; Borucki, W. J. (2011), "The Kepler-19 System: A Transiting 2.2 R🜨 Planet and a Second Planet Detected via Transit Timing Variations",Astrophysical Journal,743 (2): 200,arXiv:1109.1561,Bibcode:2011ApJ...743..200B,doi:10.1088/0004-637X/743/2/200,S2CID42698813
^Gillon, M.; Triaud, A. H. M. J.; Demory, B.-O.; Jehin, E.; Agol, E.; Deck, K. M.; Lederer, S. M.; de, Wit J.; Burdanov, A.; Ingalls, J. G.; Bolmont, E.; Leconte, J.; Raymond, S. N.; Selsis, F.; Turbet, M.; Barkaoui, K.; Burgasser, A.; Burleigh, M. R.; Carey, S. J.; Chaushev, A.; Copperwheat, C. M.; Delrez, L.; Fernandes, C. S.; Holdsworth, D. L.; Kotze, E. J.; Van, Grootel V.; Almleaky, Y.; Benkhaldoun, Z.; Magain, P.; Queloz, D. (2017), "Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1",Nature,542 (7642):456–460,arXiv:1703.01424,Bibcode:2017Natur.542..456G,doi:10.1038/nature21360,PMC5330437,PMID28230125
