Surprising Spin-orbit Resonances of Rocky Planets
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arXiv
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| Autores principales: | , , |
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| Formato: | Preprint |
| Publicado: |
2024
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| _version_ | 1866910638615298048 |
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| author | Yuan, Henry Su, Yubo Goodman, Jeremy |
| author_facet | Yuan, Henry Su, Yubo Goodman, Jeremy |
| contents | Recent works suggest that, in multiplanetary systems, a close-in exoplanet can sometimes avoid becoming tidally locked to its host star if it is captured into a secular spin-orbit resonance with a companion planet. In such a resonance, the planet remains at a sub-synchronous spin rate and an appreciable obliquity (the planet's spin-orbit misalignment angle). However, many of these works have only considered planets with fluid-like rheologies. Recent observations suggest that planets up to a few Earth masses may be rocky and thus may have an appreciable rigidity. In this work, we study the spin-orbit dynamics of such rigid planets using a linear dissipative tidal model and not enforcing principal axis rotation about the body's shortest principal axis. We identify a new class of spin-orbit resonances when the planet spins at twice its orbital frequency. These resonances exist at nonzero obliquity and spontaneously excite non-principal-axis rotation upon resonance capture. While these resonances eventually disappear as tidal dissipation damps the obliquity to zero (and the body returns to principal-axis rotation), they still modify the spin evolutionary history of the planet. Such resonances may enhance the prevalence of secular spin-orbit resonances in exoplanetary systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2410_05373 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Surprising Spin-orbit Resonances of Rocky Planets Yuan, Henry Su, Yubo Goodman, Jeremy Earth and Planetary Astrophysics Recent works suggest that, in multiplanetary systems, a close-in exoplanet can sometimes avoid becoming tidally locked to its host star if it is captured into a secular spin-orbit resonance with a companion planet. In such a resonance, the planet remains at a sub-synchronous spin rate and an appreciable obliquity (the planet's spin-orbit misalignment angle). However, many of these works have only considered planets with fluid-like rheologies. Recent observations suggest that planets up to a few Earth masses may be rocky and thus may have an appreciable rigidity. In this work, we study the spin-orbit dynamics of such rigid planets using a linear dissipative tidal model and not enforcing principal axis rotation about the body's shortest principal axis. We identify a new class of spin-orbit resonances when the planet spins at twice its orbital frequency. These resonances exist at nonzero obliquity and spontaneously excite non-principal-axis rotation upon resonance capture. While these resonances eventually disappear as tidal dissipation damps the obliquity to zero (and the body returns to principal-axis rotation), they still modify the spin evolutionary history of the planet. Such resonances may enhance the prevalence of secular spin-orbit resonances in exoplanetary systems. |
| title | Surprising Spin-orbit Resonances of Rocky Planets |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2410.05373 |