A bulging exoplanet might change our understanding of planet formation 

A bulging exoplanet might change our understanding of planet formation

One of the most bulging exoplanets observed in the Milky Way challenges our understanding of how giant planets form. The planet, called WASP-107b, orbits an orange dwarf star 211 light-years away and was classified as one of the least dense exoplanets when it was discovered in 2017.

New measurements indicate that a bulging planet is more bulging than astronomers thought, and this means that its core mass is much less than initially calculated, and this discovery may have very large implications for exoplanet research in general.

"This work examines the foundations of the formation and growth of giant planets," said astrophysicist Bourne Pinicke from the University of Montreal in Canada.

Low-density planets are known as super-bulging planets, and they are very rare and strange, as they are the size of gas giants, but their densities are much less.

The exoplanet WASP-107b is amazingly swollen and is only slightly smaller than Jupiter, but it has a mass of 10% less, resulting in a density of 0.13 grams per cubic centimeter.

In addition to the fact that the exoplanet is dangerously close to its star, its orbital period is only 5.7 days, and it is so close that its temperature reaches 736 K (462 ° C), causing its atmosphere to rapidly evaporate.

The new research, led by physicist Caroline Biaulette of the University of Montreal, has resulted in a redefinition of the mass of WASP-107b. using four years of measurements collected by the Keck Observatory to calculate the motion of the star in response to the gravitational forces in the planet's orbit.

The team conducted a detailed analysis of the structure of WASP-107b, using these new calculations and found that the solid core of the exoplanet cannot be greater than 4.6 times the mass of the Earth, meaning that more than 85% of the mass of the exoplanet is present in its bulging atmosphere.

Not that very strange; Jupiter's nucleus is believed to represent about 5% to 15% of the planet's mass, but Jupiter's mass is larger overall, which means that its nucleus is larger as well. Jupiter is also very far from its star, and that raises a lot of questions.

"How could a planet of this low-density form?" Said Biaolit. And how did he keep a huge layer of gas from escaping, especially given the planet's proximity to its star? This prompted us to make comprehensive measurements to determine the date of formation of the planet. ”

So far, our understanding of the formation of gas giants depends mainly on those that we can easily study, such as Saturn and Jupiter.

Both contain cores of mass more than 10 times the mass of the Earth; Therefore, astronomers believed that such massive nuclei are a prerequisite for the formation of a gas giant, as it would provide the mass needed to activate the unbridled accumulation of gases (the accelerating accumulation of gas from the protoplanetary disk on a growing giant planet), and quickly collect as much gas and dust as possible before it runs out. From the initial planetary disk of matter orbiting a newborn star.

But there is evidence in the WASP-107b system indicating a possible formation mechanism for WASP-107b, and its low-mass core may be one of those clues, and there is also the fact that the exoplanet is evaporating, indicating that it is difficult to have formed in its current near orbit.

In addition to another discovery made by the team, during their extended observation of the star, they found evidence of a second exoplanet very far away called WASP-107c, located in an orbit of 1088 days, this orbit is strange and eccentric, or elliptical, which indicates the interaction of gravity with an object else.

For WASP-107b, the planet formed far from the star, with the gas in the primary disk cool enough to allow the gas to accumulate, Later on, the planet was able to move to its current location, either through interactions with the disk or with other planets in the system,
The team believes that WASP-107b may be one of the best examples of exoplanets getting very close to the unbridled build-up of gases before the process stopped, perhaps by interactions with WASP-107c that propelled it toward the star.

This makes WASP-107b an excellent exoplanet for studying just how big the nucleus should be to trigger the formation of the gas giant. To help unravel this mystery, the team plans to re-study the WASP-107b. using more sensitive tools.

Exoplanets like WASP-107b, which have no analogs in our solar system, allow us to better understand the mechanisms of planetary formation in general, and the effects of exoplanet diversity motivate us to study them in greater detail,