2MASS J0441+2301

2MASS J0441+2301 is a young quadruple system hosting a planetary-mass object, a red dwarf star and two brown dwarfs, approximately 470 light years away.
The 2MASS J04414489+2301513 Bab primary has a large separation companion, 2MASS J04414565+2301580 Aab, which in turn has a nearby small separation substellar companion. 2M J044145 has similar proper motion to 2M J044144 and is likely physically associated with the system. The entire system of 4 objects is then a hierarchical quadruple of two binary objects orbiting each other. The primary component Aa has a spectral type of M4.5 and a red apparent magnitude of 14.2. Both components seem to be accreting mass from their stellar disks, as shown by their emission lines. The four objects have a total mass of only 26% of the Sun, making it the quadruple star system with the lowest mass known.

Planetary system

The primary is orbited by a companion about 5–10 times the mass of Jupiter. The mass of the primary brown dwarf is roughly 20 times the mass of Jupiter and its age is roughly one million years. It is not clear whether this companion object is a sub-brown dwarf or a planet. The companion is very large with respect to its parent and must have formed within 1 million years or so. This seems to be too big and too fast to form like a regular planet from a disk around the central object. It also fails the mass ratio criterion of the IAU definition of an exoplanet; the mass ratio with the primary is closer than 1/25. It is still considered a planet by the NASA Exoplanet Archive and Extrasolar Planets Encyclopaedia though.