A ‘super-puff’ planet like no other

James Marshall
January 20, 2021

"This work addresses the very foundations of how giant planets can form and grow", Professor Benneke said. This is a star located about 212 light years from Earth in the constellation Virgo.

The planet's elliptical orbit indicates that astronomers' new hypothesis is on track.

As such, the planet is notably not just on its own but for the "big implications" it has about the way gas-giant planets are able to form, suggesting they can come about much more easily than previously believed.

Next, the team applied a new calculation and realized an advanced examination of WASP-107b's composition. That is less remarkable - it has considerably more mass, and is much further from its star - but it has a unusual orbit around the star and could be another clue to what happened to its sibling. The exoplanet flaunts quite the traits, and it orbits an orange dwarf star nearly 211 light-years away. It has an orbital period of just 5.7 days, so close that its temperature is a scorching 736 Kelvin (462 degrees Celsius, or 865 degrees Fahrenheit), and its atmosphere is evaporating apace. In other words, the core of WASP-107b doesn't appear to have sufficient mass, and thus gravitational influence, to facilitate the formation of a gas giant inside the protoplanetary disk - the huge disk of dust and gas that encircles a star during the planet formation process.

The researchers participated The new study Bent at low density of WASP-107b. WASP-107bIt is roughly the same size as Jupiter, but only about a tenth of the mass - or about 30 times the mass of Earth.

That might sound like a lot, but by comparison Jupiter's core has been estimated to have up to 25 times the mass of the Earth. More than 85 percent of the planet's mass is found in the thick gaseous layer immediately surrounding the core. But Jupiter is more massive overall, which means its core is more massive, too. They require a much different environment, which typically exists much farther away from the star.

At the same time, the discovery raises many questions. The core had to be heavy enough to prevent gas from escaping into space but light enough to maintain the extreme low density observed on the planet.

Under current planetary formation models, a planet like Neptune or Jupiter or Saturn couldn't form close to a star. In these, a solid core at least 10 times more massive than the Earth is needed to accumulate a large amount of gas before the disc dissipates.

An artist's impression of WASP-107b transiting in front of its star. Without a massive core, gas giants were previously thought to be unable to cross that critical threshold to build up and retain gas envelopes as the discs take on their signature spherical form. There's the fact that the exoplanet is evaporating, hinting that it would be much more hard for it to form in its current close orbit.

The team made another striking discovery in their prolonged observations of the star.

Named WASP-107c, it may have influenced the orbital migration and spin-orbit misalignment of WASP-107b.

While studying the planet, the team found another planet in the same system, WASP-107c. In their long observations of the star, they found evidence of a second exoplanet - WASP-107c - much farther out, on a 1,088-day orbit.

"For WASP-107b, the most plausible scenario is that the planet formed far away from the star, where the gas in the disc is cold enough that gas accretion can occur very quickly", study co-author and astronomer Eve Lee noted. The planet was later able to move to its present location, either through interactions with the disk or With other planets in the system.

This could make it an excellent exoplanet for studying how large a core needs to be in order to trigger gas giant formation.

"Exoplanets like WASP-107b that have no analogue in our Solar System allow us to better understand the mechanisms of planet formation in general and the resulting variety of exoplanets", Piaulet said. Because the plan is to investigate WASP-107b more thoroughly. "This motivated us to do a thorough analysis to determine its formation history".

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