[1][2] UNCOVER-BD-1 was discovered[1][2] in a deep James Webb Space Telescope field called UNCOVER (Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization), which targets the galaxy cluster Abell 2744 and is primarily used to study galaxies.

As the name says, the UNCOVER team used NIRCam to take images and NIRSpec multiobject prism spectroscopy to take spectra of any object detected in the field.

[1][2] Langeroodi & Hjorth concluded from its position and distance that UNCOVER-BD-1 likely is located outside the thin disk of the Milky Way.

Those are methane (CH4), water vapor (H2O), carbon monoxide (CO) and collision induced absorption by hydrogen molecules (H2).

[2] Langeroodi & Hjorth find a low mass of around 5 MJ, but they also do not consider it as a subdwarf,[1] which might influence the estimates of physical properties.