A Mysterious Ring in Dark Space?

TL;DR

This paper reports the discovery of a faint, ring-shaped nebula in dark space, likely related to an evolved planetary nebula or filament superposition, with its properties derived from multi-band observations and distance estimates.

Contribution

It presents the first detailed analysis of this low-surface-brightness nebula, combining multi-band data and distance estimation techniques to explore its nature and origin.

Findings

The nebula has a low surface brightness of 27.42 mag arcsec^(-2).

Its distance from Earth is approximately 500 parsecs.

The nebula's energy can be explained by diffuse Galactic light.

Abstract

We report the discovery of a low-surface-brightness (27.42 mag arcsec^(-2) in g band) nebula, which has a ring-like shape in the Beijing-Arizona Sky Survey (BASS). Positive detections have been found in multiband data from far ultraviolet to far infrared, except the z band from BASS and W1, W2 from the Wide-field Infrared Survey Explorer. The reddening of the nebula E(B - V) ~ 0.02 mag is estimated from Infrared Astronomical Satellite (IRAS) 100 micron intensity and HI column density. With the help of the 3D reddening map from Pan-STARRS 1, the Two Micron All Sky Survey, and Gaia, the distance to the nebula of about 500 pc from Earth is derived. Such a low-surface-brightness nebula whose energy can be interpreted by the diffuse Galactic light could account for the optical counterpart of the infrared cirrus, which was detected by IRAS more than 30 yr ago. The ring-like structure might be the ultimate phase of an evolved planetary nebula, while the central white dwarf star has been ejected from the nebula for an unclear reason. On the other hand, the ring structure being a superposition of two close filaments might be another reasonable explanation. Considering the lack of spectroscopic data and uncertainty in the distance measurement, these interpretations need to be checked by future observations.