Webb Space Telescope Reveals Rare Planet Pair That Shouldn’t Exist
NASA’s James Webb Space Telescope (JWST) analyzed the atmosphere of a rare mini-Neptune planet orbiting inside the path of a hot Jupiter 190 light-years away, revealing heavy molecules like water vapor and sulfur dioxide that suggest it formed far from its star before migrating inward. Researchers from MIT and international institutions concluded this system challenges existing planetary formation theories, as the mini-Neptune’s survival in such proximity to a hot Jupiter defies typical gravitational expectations.
Astronomers using NASA’s James Webb Space Telescope (JWST) have uncovered new details about a rare planetary system 190 light-years from Earth, where a mini-Neptune orbits inside the path of a hot Jupiter. The findings, published in *Astrophysical Journal Letters*, reveal the smaller planet’s atmosphere contains heavy molecules like water vapor, carbon dioxide, sulfur dioxide, and traces of methane—compounds that should not exist if the planet formed near its star. The discovery, led by Saugata Barat of MIT’s Kavli Institute for Astrophysics and Space Research, suggests both planets likely originated far from their star in colder regions before migrating inward together. This contradicts the usual isolation of hot Jupiters, which typically lack inner companions due to their strong gravitational pull. The study provides the first direct evidence that mini-Neptunes can form beyond a star’s frost line, where water freezes into ice. The system, identified in 2020 by Chelsea X. Huang (now at the University of South Queensland), was initially detected by NASA’s Transiting Exoplanet Survey Satellite (TESS) around the star TOI-1130. Observations showed two planets orbiting every four and eight days, an unusual configuration for a hot Jupiter system. Researchers struggled to explain how the mini-Neptune survived so close to its massive companion. JWST’s observations focused on the inner mini-Neptune, TOI-1130b, confirming its thick, volatile-rich atmosphere. This supports the theory that both planets formed farther out before drifting inward while retaining their atmospheres. The study involved an international team from MIT, Harvard-Smithsonian Center for Astrophysics, University of South Queensland, University of Texas at Austin, and Lund University. The findings challenge existing models of planetary formation, particularly the idea that hot Jupiters should lack inner companions. By studying TOI-1130’s system, scientists now have stronger evidence that mini-Neptunes can form beyond the frost line and migrate inward, reshaping our understanding of how such systems evolve.
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