Astronomers have discovered a unique super-puff planet that is the size of Jupiter, but 10 times lighter.
The planet, called WASP-107b, is believed to be one of the least dense exoplanets ever discovered, giving it the nicknames 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 the planet is more than 16 times distant from its star than Earth from the Sun
WASP-107b is located about 212 light-years from Earth, in the constellation Virgo.
It is estimated that the planet is more than 16 times closer to its star WASP-107 than Earth is to the sun.
Using observations obtained by the Keck Observatory in Hawaii, researchers at the University of Montreal have been able to determine the size and density of the planet.
Their results suggest that WASP-107b is about the same size as Jupiter, but about 10 times lighter.
This extremely low density indicates that, according to the researchers, the planet should have a solid core no more than four times the mass of the Earth.
This suggests that more than 85 percent of its mass lies in the thick layer of gas that surrounds its core.
Caroline Piaulet, a PhD student at the University of Montreal and lead author of the study, said: “We had a lot of questions about WASP-107b. How can a planet with such a low density arise?
And how did it keep its massive gas layer from escaping, especially given the planet’s proximity to its star?
‘This motivated us to conduct a thorough analysis to determine the history of its origins.’
Most gas giant planets, such as Jupiter and Saturn, have a solid core that is at least 10 times the mass of Earth.
Estimates suggest that the planet is about the size of Jupiter, but about 10 times lighter
However, WASP-107b has a much less massive core, leading the researchers to wonder how the planet was able to cross the critical threshold needed to build and maintain its gas envelope.
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 away from the star, where the gas in the disk is cold enough that gas accretion can occur very quickly,” she said.
“The planet was later able to migrate to its present position, either through interactions with the disk or with other planets in the system.”
Surprisingly, previous data from Nasa’s Hubble spacecraft suggests that WASP-107b contains very little methane.
Mrs. Piaulet said, “That’s strange, because for this type of planet, methane should be abundant. We are now analyzing Hubble’s observations of the planet’s new mass to see how this will affect the results and to investigate which mechanisms could explain the destruction of methane. ‘
WASP-107b is about the same size as Jupiter (shown), but 10 times lighter than the gas giant
The observations also revealed that WASP-107b isn’t the only one to orbit the star WASP-107 – another planet called WASP-107c is joining.
WASP-107c has a mass about one third that of Jupiter, and is much farther from its central star than WASP-107b. It takes three years to complete a job, instead of 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 explains, “WASP-107c has in some ways preserved the memory of what happened in its system.
“Its great eccentricity indicates a rather chaotic past, with interactions between the planets that could have led to significant displacements, as was suspected for WASP-107b.”
The team hopes the findings will shed light on the different mechanisms of planet formation in the universe.
Ms. Piaulet added: ‘Exoplanets such as WASP-107b which have no analog in our solar system, allow us to better understand the mechanisms of planet formation in general and the resulting variety of exoplanets. It motivates us to study them in detail. ‘
Scientists are studying the atmosphere of distant exoplanets with the help of enormous space satellites such as Hubble
Distant stars and their orbiting planets often have conditions unlike anything we see in our atmosphere.
To understand this new world and what it is made of, scientists need to be able to detect what their atmosphere consists of.
They often do this by using a telescope similar to Nasa’s Hubble telescope.
These massive satellites scan the sky and target exoplanets that Nasa believes may be of interest.
Here, the sensors on board perform various forms of analysis.
One of the most important and useful is absorption spectroscopy.
This form of analysis measures the light coming from a planet’s atmosphere.
Each gas absorbs light of a slightly different wavelength, and when this happens, a black line appears on a full spectrum.
These lines correspond to a very specific molecule, indicating that it is present on the planet.
They are often referred to as Fraunhofer lines, 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 the clues to find out what is there.
It is vital that this is done by space telescopes, as the Earth’s atmosphere then interferes.
Absorption by chemicals in our atmosphere would skew the sample, so it is important to study the light before it has a chance to reach Earth.
This is often used to search for helium, sodium, and even oxygen in alien atmospheres.
This diagram shows how light passing from a star through an exoplanet’s atmosphere produces Fraunhofer lines that indicate the presence of important compounds such as sodium or helium.