[2] A substellar companion was discovered in 1994 by Caltech astronomers Kulkarni, Tadashi Nakajima, Keith Matthews, and Rebecca Oppenheimer, and Johns Hopkins scientists Sam Durrance and David Golimowski.

[18] This object has a surface temperature of 950 K.[19] Gliese 229B is the prototype of the T-dwarfs, due to the detection of methane in its spectrum.

The pair is a tight binary with an orbital period of 12.1 days and a semi-major axis of 0.042 astronomical units (about 16 Earth-Moon distances).

[12] The brown dwarf pair was observed with JWST MIRI low resolution spectroscopy.

Previous works showed a difference in abundances between host star and companion in Gliese 229 from near-infrared spectra.

[9] In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229.

[28] Given the proximity of the Gliese 229 system to the Sun, the orbit of GJ 229 Ab might be fully characterized by the Gaia space-astrometry mission or via direct imaging.

While considering GJ 229 Ab unconfirmed, the study estimated a significantly lower minimum mass for it.