HD 206893 b

Lore & Background

HD 206893 b was first detected in 2015 through direct imaging of the debris disk surrounding its host star, using the VLT-SPHERE instrument. The detection was confirmed ten months later, ruling out the possibility of a background object.

The companion appears very red in hue, most likely due to nearby dust, and it orbits inside the inner edge of the debris disk at an angle to the disk plane. Its estimated mass places it most likely as an L-type brown dwarf. Perturbation by this object may be causing collisions within the debris disk.

Observations with VLT/GRAVITY found the orbit to be wider and the mass lower than earlier estimates. Spectroscopy from GRAVITY shows water but no carbon monoxide for the companion. The researchers also found tentative astrometric residuals, which could be either systematic effects or caused by a potential exomoon, designated HD 206893 B I, with a mass of around 0.4 Jupiter masses and an orbital period of 0.76 years.

Reader's Guide

HD 206893 b is significant as one of the few substellar companions directly imaged within a debris disk, providing a rare opportunity to study the interaction between a planetary-mass body and its surrounding disk. Its very red color suggests substantial dust contamination, offering clues about the environment in which it formed and evolved. The companion's orbit inside the inner edge of the disk and its possible role in causing collisions within the disk highlight its dynamical influence on the system.

The tentative detection of a potential exomoon around HD 206893 b, if confirmed, would represent a first for a directly imaged substellar companion, opening new avenues for studying moon formation around such objects. The system also hosts an inner companion discovered via radial velocity monitoring in 2023, adding to the complexity of this young planetary system. The age of the star, though not well constrained, is most probably around 250 million years, making HD 206893 b a key target for understanding the early evolution of substellar objects and their disks.