TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain
Terentev, Ivan A.; Batalha, Natalie M.; Bieryla, Allyson; Latham, David W.; Knutson, Heather A.; Kane, Stephen R.; Huber, Daniel; Howell, Steve B.; Howard, Andrew W.; Petigura, Erik A.; Behmard, Aida; Chontos, Ashley; Rubenzahl, Ryan A.; Weiss, Lauren M.; Fetherolf, Tara; Lissauer, Jack J.; Ricker, George R.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Lillo-Box, J.; Dai, Fei; Albrecht, Simon; Hesse, Katharine M.; Knudstrup, Emil; Twicken, Joseph D.; Wang, Songhu; Crossfield, Ian; Batygin, Konstantin; Furlan, E.; Matthews, Elisabeth C.; Fulton, Benjamin; Robertson, Paul; Polanski, Alex S.; Isaacson, Howard; Močnik, Teo; Beard, Corey; Lubin, Jack; Akana Murphy, Joseph M.; Dressing, Courtney; Brinkman, Casey L.; Hill, Michelle L.; Scarsdale, Nicholas; Tyler, Dakotah; Wang, Xian-Yu; Osborn, Hugh; Masuda, Kento; Guerra, Pere; Vissapragada, Shreyas; Ciardi, David; Benni, Paul; Falk, Ben; Girardin, Eric; Mayo, Andrew; Goldberg, Max; Bouma, Luke; Kristiansen, Martti Holst; Greklek-McKeon, Michael; MacDougall, Mason; Zandt, Judah Van; Schwengeler, Hans Martin; Villaseñor, Joel
United States, Japan, Denmark, Australia, Switzerland, China, United Kingdom, Russia, Spain
Abstract
Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMRs). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700 ± 150 Myr old G star hosting at least six transiting planets between ~2 and 5 R ⊕. The orbital period ratios deviate from exact commensurability by only 10-4, smaller than the ~10-2 deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8M ⊕) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of a detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar flyby, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMRs. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from ~0.1 au) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density (Σ1 au ≲ 103g cm-2; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR.