The Most Widely-Separated Star-Planet System

TYC9486-927-1 and 2MASS J2126-8140 are two previously known objects in the Sun’s stellar neighbourhood. TYC9486-927-1 is a red dwarf star and 2MASS J2126-8140 is a low-gravity substellar object. Both objects are relatively young. A new study shows that the motion of both objects through space reveals that they are likely bound. New observations also indicate that TYC9486-927-1 is 10 to 45 million years old. Assuming that both objects formed together, at the same time, the mass of 2MASS J2126-8140 is estimated to be 11.6 to 15.0 times the mass of Jupiter. This places 2MASS J2126-8140 in the planetary-mass regime.

The low-gravity of 2MASS J2126-8140 indicates that the object is somewhat inflated, and still in the process of cooling and contracting in size. The separation of 2MASS J2126-8140 from its host star, TYC9486-927-1, is estimated to be over 4500 AU. This gives 2MASS J2126-8140 the wides orbit known for any planetary-mass object. So far, only a handful of such objects have been discovered. Some of these objects include WD 0806-661B, a planetary-mass object with 6 to 9 times the mass of Jupiter at 2500 AU from its host star; and GU Psc b, a planetary-mass object with 9 to 12 times the mass of Jupiter at 2000 AU from its host star.

Deacon et al. (2016), “A nearby young M dwarf with a wide, possibly planetary-mass companion”, arXiv:1601.06162 [astro-ph.EP]