Two planets orbit a distant star in an arrangement that astronomers believed was nearly impossible. About 190 light-years from Earth, in the system called TOI-1130, a giant gas planet known as a hot Jupiter orbits its star. Inside its orbit sits a smaller mini-Neptune world. This configuration should not happen because hot Jupiters usually push away smaller planets with their powerful gravity.
Yet here, the smaller planet remains. The inner mini-Neptune completes one orbit every four days, while the outer hot Jupiter takes eight days. This 2:1 rhythm suggests the planets share a common past.
Scientists used the James Webb Space Telescope to study the inner planet's atmosphere. They discovered something surprising: the atmosphere contains abundant water vapor, carbon dioxide, sulfur dioxide, and methane. About one-quarter of the upper atmosphere is water vapor, which is unusual for a planet so close to its star.
This discovery reveals an important clue. Both planets must have formed in the cold, distant regions beyond the ice line, where water freezes solid. They then migrated inward together, bringing their frozen material with them.
This finding provides strong evidence that planetary migration really occurs. The system was discovered in 2020 by Chelsea X. Huang using NASA's TESS satellite. Huang and researcher Saugata Barat led the study, piecing together how two worlds began in the frozen edges of their system and journeyed toward warmth, creating a rare partnership once thought impossible.