WASP-127b is a Heavily Inflated Super-Neptune

WASP-127b is a heavily inflated super-Neptune with 0.18 times the mass and 1.35 times the radius of Jupiter. This means the density of WASP-127b is only ~7 percent the density of Jupiter, making it one of the least dense planets known. In fact, the surface gravity on WASP-127b is over 4 times weaker than on Earth. WASP-127b is in a 4.178 day orbit around a G5 main sequence star that has 1.31 ± 0.05 times the mass and 1.33 ± 0.03 times the radius of the Sun. The heavily inflated nature of WASP-127b gives the planet a very extended atmosphere with a remarkably large scale height estimated to be 2500 ± 400 km. Such a “puffy” atmosphere makes WASP-127b an ideal target for transmission spectroscopy. Being so close to its host star, the temperature on WASP-127b is estimated to be ~1400 K.

Reference:
Lam et al. (2016), “From Dense Hot Jupiter to Low Density Neptune: The Discovery of WASP-127b, WASP-136b and WASP-138b”, arXiv:1607.07859 [astro-ph.EP]