A planetary odd couple — a mini-Neptune and a hot Jupiter — probably formed much farther away from their star before migrating closer in. Hot Jupiters, such as the one shown in this artist's illustration, orbit searingly close to their star, but they probably formed farther out — scattering away any inner companions. NASA / JPL-Caltech In 2019, astronomers discovered a planetary odd couple: a Neptune-sized world zipping around its star every four days, with a hot Jupiter orbiting close by. Hot Jupiters with inner companions are exceedingly rare — astronomers suspect that they nudge any close companions out of their orbits — so the team followed up on the system with the James Webb Space Telescope, to better understand how it could have formed. Using JWST to observe the atmosphere of the smaller world, TOI-1130b, the team found that it’s full of volatiles , such as carbon dioxide, water, and sulphur dioxide — molecules that typically gather around planets much farther away from the star.…