This 'forbidden' exoplanet is way too massive for its star

The top half of a large purple orb raises from the bottom like an eye peering upward, its diameter spanning the bottom of the image, near its top, lighter purple in the shape of an eye, with a red/orange iris and yellow pupil. a small orange/yellow sun hangs above in the center. Illustration shows a massive planet in orbit around a diminutive star.

Astronomers have discovered a massive extrasolar planet, or "exoplanet," orbiting an ultracool dwarf star that is way too small to host such a world, challenging scientists' models of how planets and planetary systems are born. 

The planet in question, designated LHS 3154 b, is 13 times as massive as Earth, meaning that it has a mass similar to the solar system ice giant Neptune, yet it closely orbits a tiny dwarf star, which is nine times less massive than the sun.