Hot Jupiters Don’t Always Destroy Their Neighbors todayheadline

In a discovery that challenges our understanding of planetary system formation, astronomers have found that massive planets known as Hot Jupiters don’t necessarily destroy or eject their neighboring worlds during their migration toward their parent stars.

The finding, published in Astronomy & Astrophysics by researchers at the University of Geneva (UNIGE), overturns long-held beliefs about these giant planets that orbit unusually close to their stars.

A Surprising Planetary Family

The research team has discovered a remarkable planetary system called WASP-132, which contains not only a Hot Jupiter but also a Super-Earth orbiting closer to the star and an icy giant planet in a more distant orbit. This unique configuration directly contradicts previous theories about how such systems form.

“The WASP-132 system is a remarkable laboratory for studying the formation and evolution of multi-planetary systems,” explains François Bouchy, associate professor in the Department of Astronomy at the UNIGE Faculty of Science. “The discovery of a Hot Jupiter alongside an inner Super-Earth and a distant giant planet calls into question our understanding of the formation and evolution of these systems.”

A Family Portrait

The system’s architecture is unprecedented. The Hot Jupiter circles its star in just over 7 days, while an inner Super-Earth – a rocky planet six times Earth’s mass – completes its orbit in just 24 hours and 17 minutes. Even more surprisingly, a giant planet five times Jupiter’s mass orbits the star every 5 years.

“This is the first time we have observed such a configuration!” notes Solène Ulmer-Moll, a postdoctoral researcher involved in the study.

Eighteen Years in the Making

The discovery represents the culmination of 18 years of observation, beginning in 2006 with the Wide-Angle Search for Planets (WASP) program. The investigation intensified when the TESS space telescope detected signals of the inner Super-Earth in late 2021.

“The detection of the inner Super-Earth was particularly exciting,” explains Nolan Grieves, first author of the paper. “We had to carry out an intensive campaign using HARPS and optimised signal processing to characterise its mass, density and composition, revealing a planet with a density similar to that of the Earth.”

Rewriting the Textbooks

The discovery challenges the standard theory that Hot Jupiters violently disrupt their planetary systems as they migrate inward. Instead, the presence of neighboring planets suggests a more peaceful migration process that preserves the system’s architecture.

“The combination of a Hot Jupiter, an inner Super-Earth and an outer giant planet in the same system provides important constraints on theories of planet formation and in particular their migration processes,” concludes Ravit Helled, professor at the University of Zurich. “WASP-132 demonstrates the diversity and complexity of multi-planetary systems, underlining the need for very long-term, high-precision observations.”