Hot Jupiters are believed to orbit alone close to their star, accreting any other planets. This observation was more convincing because there was a theory supporting it. The theory states that when giant planets move closer to their star, they either absorb or eject any planets in inner orbits.
However, a new study—by scientists at the University of Geneva (UNIGE), the National Centre of Competence in Research (NCCR) PlanetS, the Universities of Bern (UNIBE) and Zurich (UZH), and several foreign universities—overturns this theory. It suggests That Hot Jupiters do not systematically eject their planetary neighbors during migration.
Scientists have found a multi-planet system—WASP-132—with a Hot Jupiter, a super-Earth closer to the star than the Hot Jupiter, and a massive giant planet farther from the star. This means that Hot Jupiters don’t always travel alone, suggesting their migration process must differ to keep the system’s structure intact.
Within the WASP-132 system lies a Hot Jupiter, a super-Earth, and a giant planet. The hot Jupiter orbits the star in 7 days and 3 hours. The super-Earth, a rocky planet six times the mass of the Earth, orbits the star in just 24 hours and 17 minutes. The giant planet, which is five times the mass of Jupiter, orbits the host star in five years.
François Bouchy, associate professor in the Department of Astronomy at the UNIGE Faculty of Science and co-author of the study, said, “The WASP-132 system is a remarkable laboratory for studying the formation and evolution of multi-planetary systems. 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.”
Giant planets around young star raise questions about how planets form
Solène Ulmer-Moll, a postdoctoral researcher at UNIGE and UNIBE at the time of the study and co-author of the paper, said, “This is the first time we have observed such a configuration!”
The star WASP-132 was discovered in 2006 in the Wide-Angle Search for Planets (WASP) program. In 2012, over 23,000 measurements identified a planet candidate, WASP-132b, with a radius 0.87 times that of Jupiter and an orbit of 7.1 days.
In 2014, the CORALIE spectrograph began monitoring it, and by 2016, WASP-132b was confirmed, with a mass of 0.41 Jupiter masses. CORALIE also indicated another giant planet with a long orbit.
In late 2021, the TESS space telescope detected a Super-Earth near the same star, with a diameter 1.8 times that of Earth and an orbit of 1.01 days. In early 2022, the HARPS spectrograph measured this Super-Earth’s mass, finding it to be six times Earth’s mass.
Nolan Grieves, a postdoctoral researcher and the study’s lead author, noted the excitement of detecting the inner Super-Earth and characterizing its properties, which would reveal a planet with a density similar to Earth’s.
Observations of WASP-132 continue with ESA’s Gaia satellite, measuring star position variations to find planetary companions and outer brown dwarfs.
The discovery of an outer cold giant planet and an inner Super-Earth adds complexity to the WASP-132 system. The standard idea that a Hot Jupiter’s migration would disrupt other planets doesn’t hold here. Instead, their presence suggests a stable migration path for the Hot Jupiter in a proto-planetary disc, allowing it to coexist with its neighbors.
Precise measurements have revealed the density and internal composition of these planets. The Hot Jupiter WASP-132b has a heavy element enrichment of about 17 Earth masses, matching gas giant formation models. The Super-Earth’s composition is mainly metals and silicates, similar to Earth’s.
Ravit Helled, a professor and co-author of the study, says combining a Hot Jupiter, an inner Super-Earth, and an outer giant planet in the same system provides important insights into planet formation and migration processes. The WASP-132 system highlights the need for long-term, high-precision observations to understand the diversity and complexity of multi-planetary systems.
Journal Reference:
- Nolan Grieves, Francois Bouchy, et al. Discovery of a cold giant planet and mass measurement of a hot super-Earth in the multi-planetary system WASP-132. Astronomy & Astrophysics. DOI: 10.1051/0004-6361/202348177
Source: Tech Explorist
