This planet is the size of Jupiter, but ten times lighter

And so astronomers have to change.

In the universe, astronomers have uncovered many special planets. And now researchers are making another curious discovery. The gigantic exoplanet WASP-107b appears to be able to measure itself against the gas giant Jupiter in our own solar system, but it is much lighter at the same time. A striking discovery “with major implications,” says researcher Björn Benneke.

Learn more about WASP-107b
WASP-107b was discovered around the star WASP-107 in 2017. It is a star located about 212 light years from Earth in the constellation Virgo. The planet revolves around its star in a very close orbit; for example, it is at least 16 times closer to its mother star than the earth to our sun. A year on the planet lasts only 5.7 days. In comparison; the planet closest to our sun – Mercury – takes 90 days to complete a circle around the sun. WASP-107b is just as big as Jupiter, but much lighter. This means that its density is very limited. Such planets – planets of enormous size but very limited mass – are also referred to as “super puffs” or “cotton candy planets”.

The researchers are committed the new study folded on the low density of WASP-107b. Using observations from WASP-107b, they were able to accurately determine the mass. And that leads to an interesting conclusion. It turns out that the mass of WASP-107b is about ten times lighter than that of Jupiter, or about 30 times that of Earth.

Kern
The team then decided to discover the internal structure of the planet. And this led to a surprising discovery: at such a low density, the planet must have a solid core no more than four times the mass of Earth. This means that the thick layer of gas surrounding this solid core makes up about 85 percent of the total mass. In comparison, Neptune – which has a similar mass to WASP-107b – has only 5 to 15% of its total mass in its gas layer.

Central mass
This means that the nuclear mass of the giant planet is much less than what was thought necessary for the development of a huge envelope of gas around giant planets such as Jupiter and Saturn. This intriguing discovery therefore suggests that gas giants form much more easily than previously thought. “The study covers the fundamentals of the formation and growth of giant planets,” Benneke explains. “This concretely proves that planets with a much less massive nucleus can also obtain a gas envelope.

How? ‘Or’ What?
At the same time, the discovery raises many questions. “How can a planet with such a low density arise?” Asks Caroline Piaulet. “And how did the planet prevent it from being dismantled from its enormous layer of gas, especially given the planet’s narrow orbit around its star?” Eve Lee, a world-renowned expert on cotton candy planets like WASP-107b, has several assumptions. “The most plausible scenario is that the planet formed at a considerable distance from its star,” she explains. “At that time, the temperatures in the environment were low, which allowed the planet to collect a lot of gas. The planet then migrated to its current and near position at a later stage – perhaps through interactions with the protoplanetary disc or with other planets.

WASP-107c
The discovery of a second planet in the same galaxy seems to cautiously support this conjecture. For example, the planet – which was named WASP-107c – is much further from its parent star; the planet even takes three Earth years to complete an orbit around its mother star. Additionally, WASP-107c has a mass of about one-third that of Jupiter; significantly more than the mass of WASP-107b. Finally, it appears that WASP-107c has an oval-shaped orbit around its parent star. “This great eccentricity indicates a rather turbulent past, with interactions between the planets leading to significant displacements”, explains Piaulet. “And that’s exactly what we suspect for WASP-107b.”

Researchers won’t call him yet. Because the plan is to study WASP-107b even more deeply. In addition, the researchers hope soon to also be able to enlist the help of the future James Webb Space Telescope, which is expected to launch in 2021. Hopefully this brand new telescope will be able to provide a much more accurate picture of the composition of the atmosphere. of the planet. “Alien exoplanets such as WASP-107b – which we are not familiar with in our solar system – allow us to better understand the mechanisms behind the formation of planets and the resulting variety of exoplanets,” Piaulet said. “We are very motivated to study them in detail.”

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