Gliese 436 b is commonly classed as a hot Neptune.
A hot Neptune is a Neptune- or Uranus-mass planet orbiting unusually close to its host star, generally within about 1 astronomical unit. Gliese 436 b fits that description: it is a Neptune-sized world around the red dwarf Gliese 436, roughly 33 light-years away. Its orbit takes only about two days and fifteen hours, placing it far closer to its star than Neptune is to the Sun.
The planet was discovered through radial-velocity measurements in 2004. Astronomers later observed it transit its star, allowing them to determine its radius and mass more precisely. Those measurements established it as one of the earliest and smallest known transiting exoplanets of its era, and the first hot Neptune discovered with certainty.
Gliese 436 b is not a hot Jupiter: its mass and size are much closer to Neptune’s than Jupiter’s. Observations have also suggested a complex atmosphere, including escaping hydrogen that forms a large comet-like tail. In 2023, the world received the formal name Awohali, while its star was named Noquisi.