Astronomers have discovered a unique “super-fluffy” planet, as large as Jupiter, but 10 times lighter.
The planet, called WASP-107b, is believed to be one of the least dense exoplanets ever discovered, earning it the nickname of a “super-puff” or “cotton candy” planet.
Researchers say the findings have “big implications” for what we understand about how giant planets form and grow.
WASP-107b is very close to its star, WASP-107, with estimates suggesting that the planet is more than 16 times its star than Earth’s Sun.
WASP-107b is about 212 light-years from Earth in the constellation Virgo.
Estimates suggest that the planet is more than 16 times closer to its star, WASP-107, than the Sun Earth.
Using observations from the Keck Observatory in Hawaii, researchers at the University of Montreal were able to determine the size and density of the planet.
Their results suggest that the WASP-107b is about the same size as Jupiter, but is about 10 times lighter.
This extremely low density indicates that the planet must have a solid core no more than four times the mass of the Earth, according to researchers.
This suggests that more than 85% of its mass is in the thick layer of gas that surrounds its core.
Caroline Piaulet, a doctoral student at the University of Montreal and lead author of the study, said: “I had a lot of questions about WASP-107b. How could a planet with such a low density be formed?
“And how did he keep his huge layer of gas from escaping, especially considering the proximity of the planet to its star?”
“This motivated us to make an in-depth analysis to determine the history of its formation.”
Most gas giant planets, such as Jupiter and Saturn, have a solid core at least 10 times more massive than Earth.
Estimates suggest that the planet is about the same size as Jupiter, but is about 10 times lighter.
However, WASP-107b has a much less massive core, which led researchers to question how the planet managed to cross the critical threshold needed to build and maintain its gas shell.
Professor Eve Lee, a world-renowned expert on super-puff planets, has several theories.
“For WASP-107b, the most plausible scenario is that the planet formed far from the star, where the gas in the disk is cold enough for gas accretion to take place very quickly,” she said.
“The planet was later able to migrate to its current position, either through interactions with the disk or with other planets in the system.”
Surprisingly, previous data from NASA’s Hubble spacecraft suggest that the WASP-107b contains very little methane.
Ms Piaulet said: “It is strange, because for this type of planet, methane should be abundant. We are now reanalyzing Hubble’s observations with the new mass of the planet to see how it will affect the results and to examine what mechanisms might explain the destruction of methane.
WASP-107b is about the same size as Jupiter (pictured), but 10 times lighter than the gas giant
Observations have also shown that WASP-107b is not the only one orbiting the star WASP-107 – it is joined by another planet, called WASP-107c.
WASP-107c has a mass about one-third that of Jupiter and is much farther from its central star than WASP-107b, taking three years to complete an orbit, as opposed to just 5.7 days.
Interestingly, the eccentricity of this second planet is high, which means that its trajectory is more oval than circular.
Ms. Piaulet explained: “The WASP-107c has kept, in some respects, the memory of what happened in its system.
“Its great eccentricity indicates a rather chaotic past, with interactions between planets that could have led to significant displacements, such as the one suspected for WASP-107b.”
The team hopes that the findings will shed light on the various mechanisms of planet formation in the universe.
Ms. Piaulet added: “Exoplanets such as WASP-107b that have no analog in our solar system allow us to better understand the mechanisms of planet formation in general and the variety resulting from exoplanets. It motivates us to study them in detail.
Scientists study the atmosphere of distant exoplanets using huge space satellites like Hubble
Distant stars and their orbiting planets often have different conditions than anything we see in our atmosphere.
To understand this new world and what it is made of, scientists must be able to detect what their atmosphere is.
They often do this using a telescope similar to NASA’s Hubble Telescope.
These huge satellites scan the sky and fixate on exoplanets that NASA thinks might be of interest.
Here, the on-board sensors perform various forms of analysis.
One of the most important and useful is called absorption spectroscopy.
This form of analysis measures the light that comes out of a planet’s atmosphere.
Each gas absorbs a slightly different wavelength of light, and when this happens, a black line appears on a full spectrum.
These lines correspond to a very specific molecule, which indicates its presence on the planet.
They are often named after Fraunhofer after the German astronomer and physicist who first discovered them in 1814.
By combining all the different wavelengths of light, scientists can determine all the chemicals that make up a planet’s atmosphere.
The key is that what is missing provides clues to find out what is present.
It is vitally important that this is done through space telescopes, because the Earth’s atmosphere would then interfere.
The absorption of chemicals from our atmosphere would distort the sample, which is why it is important to study light before it has a chance of reaching Earth.
It is often used to search for helium, sodium and even oxygen in foreign atmospheres.
This diagram shows how light passing through a star and through the atmosphere of an exoplanet produces Fraunhofer lines that indicate the presence of key compounds such as sodium or helium.