WASP-132 is a unique multi-planet system in that both an inner rocky planet and the newly-discovered outer giant planet are in a system with a hot-Jupiter planet. This suggests the hot Jupiter migrated via a rare dynamically cool mechanism and helps to further the understanding of how hot Jupiter systems form and evolve.
The WASP-132 system contains a hot Jupiter (foreground), an inner super-Earth (transiting in front of the orange host star) and the cold planet WASP-132d. Image credit: Thibaut Roger, Université de Genève.
Hot Jupiters are planets with masses similar to those of Jupiter, but which orbit closer to their star than Mercury orbits the Sun.
There is not enough gas and dust for these giant planets to form where they are observed, so the accepted theory is that they originate far from their star and migrate inward as the planetary system evolves.
Until now, hot Jupiters were thought to orbit their star alone, as migration towards the star would eject other planets in the system.
The two extra planets in the WASP-132 planetary system now call into question this theory.
“The WASP-132 system is a remarkable laboratory for studying the formation and evolution of multi-planetary systems,” said Dr. François Bouchy, an astronomer at the Observatoire de Genève.
“The discovery of a hot Jupiter alongside an inner super-Earth and a distant giant calls into question our understanding of the formation and evolution of these systems.”
“This is the first time we have observed such a configuration.”
The hot Jupiter, WASP-132b, orbits its parent star in 7.1 days. The super-Earth, WASP-132c, orbits the star in just 24 hours and 17 minutes.
The newly-discovered icy giant, named WASP-132d, orbits the host star in five years.
“The detection of the inner super-Earth was exciting as it’s particularly rare to find planets interior to hot Jupiters,” said University of Warwick’s Dr. David Armstrong.
“We carried out an intensive campaign with state-of-the-art instruments to characterize its mass, density and composition, revealing a planet with a density similar to that of the Earth.”
“This planetary discovery adds a layer of complexity to the WASP-132 system as migration of a hot Jupiter towards its star through dynamical perturbation would destabilize the orbits of the other two planets.”
“This suggests a more stable ‘cool’ migration path for the hot Jupiter in a protoplanetary disk that surrounds a young star and is the site of planet formation.”
The discovery is described in a paper published today in the journal Astronomy & Astrophysics.
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Nolan Grieves et al. 2025. Discovery of a cold giant planet and mass measurement of a hot super-Earth in the multi-planetary system WASP-132. A&A 693, A144; doi: 10.1051/0004-6361/202348177
