TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain

• Published in: arXiv.org 2022-11
• Main Authors: Dai, Fei, Masuda, Kento, Beard, Corey, Robertson, Paul, Goldberg, Max, Batygin, Konstantin, Bouma, Luke, Lissauer, Jack J, Knudstrup, Emil, Albrecht, Simon, Howard, Andrew W, Knutson, Heather A, Petigura, Erik A, Weiss, Lauren M, Isaacson, Howard, Martti Holst Kristiansen, Osborn, Hugh, Wang, Songhu, Xian-Yu, Wang, Behmard, Aida, Greklek-McKeon, Michael, Vissapragada, Shreyas, Batalha, Natalie M, Brinkman, Casey L, Chontos, Ashley, Crossfield, Ian, Dressing, Courtney, Fetherolf, Tara, Fulton, Benjamin, Hill, Michelle L, Huber, Daniel, Kane, Stephen R, Lubin, Jack, MacDougall, Mason, Mayo, Andrew, Teo Močnik, Akana Murphy, Joseph M, Rubenzahl, Ryan A, Scarsdale, Nicholas, Tyler, Dakotah, Judah Van Zandt, Polanski, Alex S, Hans Martin Schwengeler, Terentev, Ivan A, Benni, Paul, Bieryla, Allyson, Ciardi, David, Falk, Ben, Furlan, E, Girardin, Eric, Guerra, Pere, Hesse, Katharine M, Howell, Steve B, Lillo-Box, J, Matthews, Elisabeth C, Twicken, Joseph D, Villaseñor, Joel, Latham, David W, Jenkins, Jon M, Ricker, George R, Seager, Sara, Vanderspek, Roland, Winn, Joshua N
• Format: Article
• Language: English
• Subjects: Binary stars; Extrasolar planets; G stars; Orbital resonances (celestial mechanics); Orbits; Planetary evolution; Planetary rotation; Planetary systems; Solar nebula; Stellar rotation; Terrestrial planets; Transit
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2210.09283

Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between \(\sim\)2 and 5 \(R_\oplus\). The orbital period ratios deviate from exact commensurability by only \(10^{-4}\), smaller than the \(\sim\)\,\(10^{-2}\) deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8\(M_\oplus\)) 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 detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, 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 MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from \(\sim\)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 (\(\Sigma_{\rm 1AU}\lesssim10^3\)g~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. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f.