Disk shadows point to a hidden inclined planet

Katie Milsom and colleagues compared multi-epoch GPI and SPHERE scattered-light images of the protoplanetary disk around HD 139614. The brightness pattern in its inner ring changes on a timescale shorter than eleven months, while an inner arc appears to be a tightly wound spiral. A broad shadow covers roughly two-thirds of the outer disk, and a second shadow is misaligned with it.

The team modeled the disk as three annuli separated by gaps, with an inclined planet between the inner two. In the simulations, the planet tilts and slowly precesses the inner annuli, whose overlapping shadows reproduce the observed geometry. That is indirect dynamical evidence, not a direct image of the planet; other disk structures must still be tested against the same observations.

Why it matters

Planet formation often has to be reconstructed from what an unseen body does to surrounding material. A shadow pattern offers an independent route to finding misaligned planets that may evade direct imaging.

What the source establishes

Fresh preprint submitted October 5. The changing brightness and shadow geometry are observed; the inclined planet is the perturbing body in the authors' physical model.