About this world
KMT-2021-BLG-0240L b is a Neptune-like planet orbiting KMT-2021-BLG-0240L, a star 21.5 thousand light-years from Earth. It is about 0.86 times the size of Jupiter (its size estimated from its mass) and holds 0.21 Jupiter masses.
At its size it almost certainly keeps a deep envelope of hydrogen and helium.
It was discovered in 2022 by microlensing with KMTNet. A foreground star's gravity magnifies a background star; a planet adds a blip.