Sub-brown dwarf

[3] Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud (perhaps with the help of photo-erosion) but there is no consensus amongst astronomers on whether the formation process should be taken into account when classifying an object as a planet.

[4] Free-floating sub-brown dwarfs can be observationally indistinguishable from rogue planets, which originally formed around a star and were ejected from orbit.

[6] This is because to collapse by gravitational contraction requires radiating away energy as heat and this is limited by the opacity of the gas.

[9] Nonetheless, the IAU working definition of an exoplanet ignored formation mechanism as a criterion, and based on it these objects would be considered planets.

[13] Other examples of planetary-mass objects orbiting brown dwarfs and with MB<13 MJ and q>0.04: Also called rogue planets:

Comparison: the Sun (yellow), a young sub-brown dwarf (red), and Jupiter (multi-colored). As the sub-brown dwarf ages, it will gradually cool and shrink.