The exoplanet “Super Puff” is as big as Jupiter but 10 times lighter, which confuses astronomers

About 212 light years from Earth, a gas giant light enough to be dubbed a “super puff” or “cotton candy” planet spins extremely close to its host star. the exoplanet is so light that astronomers are questioning everything we previously knew about the formation of gas giants.

This super puff exoplanet, known as WASP-107b, is roughly the same size as Jupiter, but only about a tenth of its mass – or about 30 times the mass of Earth. According to a new study published Monday in The Astronomical Journal, its central mass is significantly smaller than what astronomers thought necessary to create a giant gas planet like Jupiter and Saturn.

The discovery, made by Ph.D. student Caroline Piaulet under the supervision of Professor Björn Benneke of the University of Montreal, indicates that gas giants form much more easily than previously believed.

“This study pushes the boundaries of our theoretical understanding of how giant-sized planets form. WASP-107b is one of the most inflated planets on the market, and we need a creative solution to explain how these tiny nuclei can build such massive gas envelopes. ” co-author Eve Lee said in a statement.

WASP-107b isn’t a brand new discovery – astronomers first detected it in the constellation Virgo in 2017. The planet is very close to its star, more than 16 times closer than Earth east of the sun, completing one orbit every 5.7 days.

WASP-107b is one of the least dense exoplanets scientists have ever found. They dubbed similar types of planets – gas giants with the density of cotton candy – super puffs.

To find the surprising mass of the planet, astronomers studied observations obtained at the Keck Observatory in Hawaii. They used a technique called the radial velocity method, which studies the oscillating motion of a planet’s star caused by a planet’s gravitational pull, to calculate mass.

Scientists were shocked to conclude that the solid core of WASP-107b had a mass that is no more than four times that of Earth, meaning that more than 85% of its mass comes from the thick gas layer. surrounding the nucleus. This is a radically different breakdown of Neptune, which has a similar mass but only contains 5% to 15% of it in its gas layer.

Based on their knowledge of Jupiter and Saturn, scientists previously believed that a solid core of at least 10 times the mass of Earth would be needed to acquire enough gas for a giant gas planet to form. WASP-107b disputes this theory.

“This work addresses the very foundations of the formation and growth of giant planets,” Benneke said. “This provides concrete evidence that massive accretion of an envelope of gas can be triggered for much less massive nuclei than previously thought.”

Lee postulates that “the most plausible scenario is that the planet formed far from the star, where the gas in the disk is cold enough that gas accretion can occur very quickly. The planet was then able to migrate to its current position, either through interactions with the disk or with other planets in the system. “

While studying the planet, the team came across another in the same system, WASP-107c. It has a mass of about a third that of Jupiter and takes three years to orbit once on its host star.

The planet’s oval-shaped orbit suggests that astronomers’ new hypothesis is on the right track.

“WASP-107c has, in some ways, kept the memory of what happened in its system,” Piaulet said. “Its great eccentricity hints at a rather chaotic past, with interactions between planets that could have led to significant displacements, like the one suspected for WASP-107b.”

The team hopes to continue studying the strange planet with the launch of the James Webb Space Telescope this year.