Discovery of two planets challenges planetary formation theories

Discovery of two planets challenges planetary formation theories
by Sophie Jenkins
London, UK (SPX) Jan 16, 2025

The identification of two planets in the WASP-132 system by a collaborative team of astronomers from the University of Warwick and the University of Geneva (UNIGE) is reshaping scientific understanding of planetary system formation. These findings could redefine long-held views on the development of 'hot Jupiter' systems.

The two exoplanets discovered consist of an inner super-Earth and an outer icy giant planet. Their coexistence with a hot Jupiter in the same system contradicts established beliefs that such giant planets form in distant orbits before migrating inward and ejecting other planets.

Hot Jupiters, gas giants with masses comparable to Jupiter but located much closer to their stars, have traditionally been considered solitary due to the disruptive nature of their inward migration. The recent discovery of additional planets within the WASP-132 system raises questions about this solitary model.

"The detection of the inner super-Earth was exciting as it's particularly rare to find planets interior to hot Jupiters," said David Armstrong, Associate Professor of Physics at the University of Warwick. "We carried out an intensive campaign with state-of-the-art instruments to characterise its mass, density, and composition, revealing a planet with a density similar to that of the Earth."

This research challenges the view that hot Jupiter migration through dynamical perturbation inherently destabilizes the orbits of neighboring planets. Instead, it suggests that a more gradual migration within a proto-planetary disc may preserve the orbits of other planets, offering a new perspective on how these systems evolve.

"The WASP-132 system is a remarkable laboratory for studying the formation and evolution of multi-planetary systems," explained Francois Bouchy, Associate Professor in the Department of Astronomy at UNIGE. "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."

Key findings include:

- The hot Jupiter completes its orbit in just over seven days.

- The super-Earth, a rocky planet six times Earth's mass, completes an orbit in approximately 24 hours.

- The icy giant, with a mass five times that of Jupiter, circles the star over five years.

Advanced measurements have provided precise data on the planets' radii, masses, and compositions. The super-Earth is composed primarily of metals and silicates, resembling Earth's internal makeup.

Further observations of WASP-132 are ongoing, with the European Space Agency's Gaia satellite monitoring stellar positions for subtle shifts indicative of planetary companions and brown dwarfs.

Research Report:Discovery of a cold giant planet and mass measurement of a hot super-Earth in the multi-planetary system WASP-132