More Likely Than You Think: Inclination-driving Secular Resonances Are Common in Known Exoplanet Systems

Multiplanet systems face significant challenges to detection. For example, farther-orbiting planets have a reduced signal-to-noise ratio in radial velocity detection methods, and small mutual inclinations between planets can prevent them from all transiting. One mechanism for exciting mutual inclina...

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Bibliographic Details
Published in:The Astrophysical journal 2025-01, Vol.978 (1), p.18
Main Authors: Faridani, Thea H., Naoz, Smadar, Li, Gongjie, Rice, Malena, Inzunza, Nicholas
Format: Article
Language:English
Subjects:
Angular momentum
Angular velocity
Exoplanet dynamics
Exoplanet systems
Exoplanets
Extrasolar planets
Inclination
Momentum transport
Oblateness
Planetary evolution
Planetary system formation
Planets
Precession
Radial velocity
Resonance
Signal to noise ratio
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Summary:Multiplanet systems face significant challenges to detection. For example, farther-orbiting planets have a reduced signal-to-noise ratio in radial velocity detection methods, and small mutual inclinations between planets can prevent them from all transiting. One mechanism for exciting mutual inclination between planets is secular resonance, where the nodal precession frequencies of the planets align so as to greatly increase the efficiency of the angular momentum transport between planets. These resonances can significantly misalign planets from one another, hindering detection, and typically can only occur when there are three or more planets in the system. Naively, systems can only be in resonance for particular combinations of planet semimajor axes and masses; however, effects that alter the nodal precession frequencies of the planets, such as the decay of stellar oblateness, can significantly expand the region of parameter space where resonances occur. In this work, we explore known three-planet systems, determine whether they are in (or were in) secular resonance due to evolving stellar oblateness, and demonstrate the implications of resonance on their detectability and stability. We show that about 20% of a sample of three-planet transiting systems seem to undergo these resonances early in their lives.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad8ebf