Gas-giant exoplanet WASP-107b has a surprisingly low core mass

Shane McGlaun - Jan 21, 2021, 5:57am CST
Gas-giant exoplanet WASP-107b has a surprisingly low core mass

Researchers have been studying a gas-giant exoplanet called WASP-107b. During the study, they discovered the exoplanet’s core mass is much lower than what was previously believed to be necessary to build up the immense gas envelope surrounding gas-giant planets. Research conducted by the Université de Montréal suggests that gas-giant planets may form more easily than previously believed.

Researchers believe the new analysis of WASP-107b’s internal structure has significant implications for future research. University professor Björn Benneke says the work addresses the foundation of how giant planets form and grow. He says it provides concrete proof that massive accretion of gas envelopes can be triggered for cores that are much less massive than previously believed.

WASP-107b was first detected in 2017 orbiting a star called WASP-107 about 212 light-years from Earth in the Virgo constellation. The planet orbits about 16 times closer to its host star than the Earth orbits the sun. The planet is the size of Jupiter but ten times lighter, making it one of the least dense exoplanets known.

Planets of such light density are known by astrophysicists as “super-puff” or “cotton-candy” planets. The researchers used the radial velocity method to determine the planet’s mass by observing the wobbling motion of the host star from the planet’s gravitational pull. They were able to conclude the mass of WASP-107b is about a tenth that of Jupiter or approximately 30 times that of Earth.

The team estimates the planet’s solid core must be no more than four times the Earth’s mass, meaning more than 85 percent of its mass is included in the thick layer of gas surrounding the core. Researchers believe the most plausible scenario for the exoplanet’s formation is that it formed far away from the star where gas in the disc is cold enough that accretion can occur quickly. The planet later migrated to its current position through interactions with the disk or other system planets.


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