Exoplanets & Exomoons

Formation Of Polar Terrestrial Circumbinary Planets

By Keith Cowing
September 26, 2021
Filed under
Formation Of Polar Terrestrial Circumbinary Planets
Particle orbits in model EP. The binary orbit has a semi-major axis of 0.5 au and an eccentricity of 0.8. The binary stars are marked by black stars and the binary orbit is shown with a solid black line. The particles and their orbits are marked in purple. The size of the markers and the width of the lines are proportional to the particle’s mass. Left: Time t = 10 Kyr. Right: Time t = 7 Myr.

All circumbinary planets currently detected are in orbits that are almost coplanar to the binary orbit.

While misaligned circumbinary planets are more difficult to detect, observations of polar aligned circumbinary gas and debris disks around eccentric binaries suggest that polar planet formation may be possible. A polar aligned planet has a stable orbit that is inclined by 90 degrees to the orbital plane of the binary with an angular momentum vector that is aligned to the binary eccentricity vector.

With n- body simulations we model polar terrestrial planet formation using hydrodynamic gas disk simulations to motivate the initial particle distribution. Terrestrial planet formation around an eccentric binary is more likely in a polar alignment than in a coplanar alignment. Similar planetary systems form in a polar alignment around an eccentric binary and a coplanar alignment around a circular binary. The polar planetary systems are stable even with the effects of general relativity.

Planetary orbits around an eccentric binary exhibit tilt and eccentricity oscillations at all inclinations, however, the oscillations are larger in the coplanar case than the polar case. We suggest that polar aligned terrestrial planets will be found in the future.

Anna Childs, Rebecca Martin

Comments: 8 pages, 4 figures, 1 table. Accepted for publication in ApJL. arXiv admin note: text overlap with arXiv:2108.09257
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2109.11653 [astro-ph.EP] (or arXiv:2109.11653v1 [astro-ph.EP] for this version)
Submission history
From: Anna Childs
[v1] Thu, 23 Sep 2021 21:29:29 UTC (3,268 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻