About this world
V1298 Tau d is a Neptune-like planet orbiting V1298 Tau, an orange dwarf (type K1) 353 light-years from Earth. It is about 0.58 times the size of Jupiter and holds 0.019 Jupiter masses. It completes an orbit every 12.4 days at 0.11 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 831 K (558 °C): far too hot for liquid water on its surface. At its size it almost certainly keeps a deep envelope of hydrogen and helium. Its atmosphere has already been studied: 4 spectroscopic observations, all of them with the James Webb Space Telescope.
It was discovered in 2019 by transit with K2. A planet crosses its star and dims it by a tiny, periodic fraction. V1298 Tau has 4 known planets; the others are V1298 Tau c, V1298 Tau b and V1298 Tau e.