Robust evidence of an ice giant planet shedding its atmosphere around the white dwarf WD J0914+1914 represents a milestone in exoplanetary science , allowing us to finally supplement our knowledge of white dwarf metal pollution , debris discs and minor planets with the presence of a major planet .
Here , we discuss the possible dynamical origins of this planet , WD J0914+1914 b .
The very young cooling age of the host white dwarf ( 13 Myr ) combined with the currently estimated planet-star separation of about 0.07 au imposes particularly intriguing and restrictive coupled constraints on its current orbit and its tidal dissipation characteristics .
The planet must have been scattered from a distance of at least a few au to its current location , requiring the current or former presence of at least one more major planet in the system in the absence of a hidden binary companion .
We show that WD J0914+1914 b could not have subsequently shrunk its orbit through chaotic f-mode tidal excitation ( characteristic of such highly eccentric orbits ) unless the planet was or is highly inflated and possibly had partially thermally self-disrupted from mode-based energy release .
We also demonstrate that if the planet is currently assumed to reside on a near-circular orbit at 0.07 au , then non-chaotic equilibrium tides impose unrealistic values for the planet ’ s tidal quality factor .
We conclude that WD J0914+1914 b either ( i ) actually resides interior to 0.07 au , ( ii ) resembles a disrupted “ Super-Puff ” whose remains reside on a circular orbit , or ( iii ) resembles a larger or denser ice giant on a currently eccentric orbit .
Distinguishing these three possibilities strongly motivates follow-up observations .