Tidally-Distorted, Iron-Enhanced Exoplanets Closely Orbiting Their Stars

Abstract

The transiting planet candidate KOI 1843.03 ($0.6R_{\oplus }$ radius, 4.245 hour orbital period, $0.46M_{\odot }$ host star) has the shortest orbital period of any planet yet discovered. Here we show, using the first three-dimensional interior structure simulations of ultra-short-period tidally distorted rocky exoplanets, that KOI 1843.03 may be shaped like an American football, elongated along the planet-star axis with an aspect ratio of up to 1.79. Furthermore, for KOI 1843.03 to have avoided tidal disruption (wherein the planet is pulled apart by the tidal gravity of its host star) on such a close-in orbit, KOI 1843.03 must be as iron-rich as Mercury (about 66% by mass iron compared to Mercury's 70% by mass iron, Hauck et al. 2013). Of the ultra-short-period ($P_{\mathrm{orb}}\lesssim 1$ day) planets with physically-meaningful constraints on their densities characterized to date, just under half (4 out of 9) are iron-enhanced. As more are discovered, we will better understand the diversity of rocky planet compositions and the variety of processes that lead to planetary iron enhancement.

arXiv commentSubmitted to ApJ

References in corpus (23)

• The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0 microns Using GLIMPSE Data
• Mass-Radius Relationships for Solid Exoplanets
• A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
• A Study of the Shortest-Period Planets Found With Kepler
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
• Disentangling stellar activity and planetary signals
• The extreme physical properties of the CoRoT-7b super-Earth
• Minimum Radii of Super-Earths: Constraints from Giant Impacts
• Atmosphere-interior exchange on hot rocky exoplanets
• The Roche limit for close-orbiting planets: Minimum density, composition constraints, and application to the 4.2-hour planet KOI 1843.03
• Catastrophic Evaporation of Rocky Planets
• Kepler-78 and the Ultra-Short-Period Planets
• An Earth-sized exoplanet with a Mercury-like composition
• Forming Mercury by Giant Impacts
• Low False-Positive Rate of Kepler Candidates Estimated From A Combination Of Spitzer And Follow-Up Observations
• Photophoretic separation of metals and silicates: the formation of Mercury like planets and metal depletion in chondrites
• Mercurian impact ejecta: Meterorites and mantle
• Distorted, non-spherical transiting planets: impact on the transit depth and on the radius determination
• Photometry using the Infrared Array Camera on the Spitzer Space Telescope
• K2-106, a system containing a metal-rich planet and a planet of lower density
• K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf
• Instability of mass transfer in a planet-star system

Cited by in corpus (7)

• Lava Worlds: From Early Earth to Exoplanets
• Composition and Size Dependent Sorting in Preplanetary Growth: Seeding the Formation of Mercury-like Planets
• The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs
• Migrating Planets into Ultra-Short-Period Orbits during Episodic Accretion Events
• A possible transit of a disintegrating exoplanet in the nearby multiplanet system DMPP-1
• The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys
• Radius and mass distribution of ultra-short period planets