Exoplanets & Exomoons

Misalignment Of Terrestrial Circumbinary Planets As An Indicator Of Their Formation Mechanism

By Keith Cowing
February 22, 2022
Filed under
Misalignment Of Terrestrial Circumbinary Planets As An Indicator Of Their Formation Mechanism
Particle misalignments (left) and nodal phase angles (right) as a function of semi-major axis at a time of 100 Kyr of integration time with no expansion factor in the systems without Jupiter and Saturn. The size and color of the points are correlated to the body mass. There is not much change to the body masses (which begin at either ≈ 0.1 M⊕ or ≈ 0.01 M⊕) or inclinations at this time.

Circumbinary gas disks are often observed to be misaligned to the binary orbit suggesting that planet formation may proceed in a misaligned disk.

With N-body simulations we consider the formation of circumbinary terrestrial planets from a particle disk that is initially misaligned. We find that if terrestrial planets form in this way, in the absence of gas, they can only form close to coplanar or close to polar to the binary orbit. Planets around a circular binary form coplanar while planets around an eccentric binary can form coplanar or polar depending on the initial disk misalignment and the binary eccentricity.

The more massive a terrestrial planet is, the more aligned it is (to coplanar or polar) since it has undergone more mergers that lead on average to smaller misalignment angles. Nodal precession of particle disks with very large initial inclinations lead to high mutual inclinations between the particles. This produces high relative velocities between particles that leads to mass ejections that can completely inhibit planet formation. Misaligned terrestrial circumbinary planets may be able to form in the presence of a misaligned circumbinary gas disk that may help to nodally align the particle orbits and maintain the inclination of the planets during their formation.

Anna C. Childs, Rebecca G. Martin

Comments: Accepted for publication in ApJL. 9 pages, 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2202.10495 [astro-ph.EP] (or arXiv:2202.10495v1 [astro-ph.EP] for this version)
Submission history
From: Anna Childs
[v1] Mon, 21 Feb 2022 19:13:30 UTC (3,765 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) 🖖🏻