Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE). II. A 135 Myr Planet on an Aligned Orbit with Transit Timing Variations

Young planets (<1 Gyr) provide opportunities to directly probe planet formation and evolution processes in action. However, due to heightened stellar activity, there is a lack of known transiting planets in adolescence (∼100–500 Myr). Here we present the validation of TIC 150070085 b, a 3.6 R ⊕ planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R ⊕ planet on a 15.90 day orbit. While we are unable to validate the second signal, the proximity to mean-motion resonance (3:2) and transit timing variations observed in the transits of TIC 150070085 b strongly suggest that the signal is planetary. We confirm the host star as a member of Alessi 84 and combine the group’s color–magnitude diagram, rotation, and variability properties to update the age to 135 ± 10 Myr. We additionally use MAROON-X to observe the Rossiter–McLaughlin signal of TIC 150070085 b and measure the sky projected obliquity angle ( λ ). We find that TIC 150070085 b is consistent with a near-aligned orbit with its host star (∣ λ ∣ = 18° ± 12°), in line with similarly aged transiting planets with measured λ values. Continued discovery and characterization of planets in this age regime are vital to link planetary infancy (<50 Myr) and maturity (>1 Gyr).