ROXs 42Bb is a directly imaged planetary-mass companion[1] to the binary M star ROXs 42B,[4] a likely member of the Rho Ophiuchi cloud complex.

The companion was announced/discovered on October 17, 2013, by University of Toronto astronomer Thayne Currie.

However, it is unclear whether ROXs 42Bb formed like these planets via core accretion, by disk (gravitational) instability, or more like a binary star.

Preliminary fits of the spectra and broadband photometry to atmospheric models imply a radius of 2.43 ± 0.18 RJ for an effective temperature of about 2,000 K or a radius of 2.55 ± 0.20 RJ for about 1950 K.[5] Like Beta Pictoris b, ROXs 42Bb's atmosphere is likely very cloudy and dusty.

[5] The object is located in the constellation Ophiuchus, near the border with Scorpius.