For one, it's up to 15 times the mass of Jupiter, the largest planet in our own solar system. You might think that makes it a frigid gas giant, but that's not so. 2MASS is so large that it's on the border between a planet and brown dwarf star, and has a likely surface temperature of around 2,730 degrees F. Meanwhile, the star it orbits around, TYC 9486-927-1, is very young, with an age between 10 and 45 million years. Given that 2MASS takes 900,000 years to do one orbit, it has only made a maximum of 50 trips around the star so far, total.

By comparison, a well-known planet of similar size orbiting the star Beta Pictoris b star is much closer. "Compared to Beta Pictoris b, 2MASS J2126 is more than 700 times further away from its host star," said co-author Simon Murphy of the Australian National University, "but how such a wide planetary system forms and survives remains an open question."