A mysterious planet the size of Jupiter that shouldn’t exist is as puffy as a marshmallow and astronomers finally think they know why

  • Exoplanet WASP 107b is a gas giant that is almost the size of Jupiter, but much less massive.

  • Based on this discrepancy, astronomers did not know how a planet like WASP 107b could exist.

  • But now, two independent teams of researchers have harnessed the power of JWST to solve the mystery.

Right in our cosmic neighborhood, about 210 light years away, is a planet beyond our solar system that has defied scientific explanation for decades. Its name is WASP 107b.

Now, two different teams of astronomers think they’ve found the solution, but they’ve raised a new set of questions that will require further research.

WASP 107b: The exoplanet that shouldn’t exist

Artist's impression of a planet passing in front of its host star and coronal mass.

Artist’s impression of WASP 107b passing in front of its host star. This planet is almost the same size as Jupiter, but has only 12% of its mass.ESA/Hubble, NASA, and M. Kornmesser

Astronomers first detected this unusual exoplanet in 2017.

Their initial observations indicated that WASP 107b was about as wide as Jupiter, but 10 times less massive, earning it the nickname “super-puff,” like a puffy marshmallow or fluffy cotton candy.

For years, experts struggled to understand how such a planet could grow so large in diameter yet remain so light in mass. As far as scientific models were concerned, the exoplanet should not exist.

“People started bending over backwards to try to figure out how to make such a planet,” David Sing, Bloomberg distinguished professor at Johns Hopkins University, told Business Insider.

Usually, planets grow wider just like people. The more content they consume, the wider – and bigger – they get. Therefore, if this exoplanet was as large as the astronomers observed, it should not have such a low mass.

Artist's rendering of a gas giant being formedArtist's rendering of a gas giant being formed

Gas giants form when clouds of gas gather around a dense rocky core. But models suggested that WASP 107b’s core would be too small to form a gas giant.NASA Goddard Space Flight Center, ESO/L. Walked

“WASP 107b is an outlier among outliers,” said Luis Welbanks, a NASA Sagan postdoctoral fellow at Arizona State University.

Now, thanks to the James Webb Space Telescope, two separate research teams—one led by Sing and another by Welbanks—think they’ve finally nailed the case. Furthermore, both teams reached very similar conclusions, which contributed to each other’s results.

Both teams maintain that the answer to this mystery was hidden in the core of WASP 107b. It turns out that the center of this exoplanet was much hotter and more massive than astronomers had previously thought.

But in order to reach that conclusion, both teams had to have a serious space slush.

Scientific models did not match the observations

NASA's hubble space telescopeNASA's hubble space telescope

Hubble images of WASP 107b did not solve the mystery of its large size and low density. Astronomers needed a more powerful instrument: JWST.Venom82

Why it took years for astronomers to understand the mysterious origin of WASP 107b stems from what many astronomers face: a lack of information due to technological limitations.

Thanks to preliminary observations with the Hubble Space Telescope, astronomers knew some information about WASP 107b when it was discovered but not enough to answer the big question.

So, they first turned to scientific models to fill in the gaps. There was one big gap in the core of the exoplanet.

Scientific models suggested that the core would have to be relatively small and cold, Sing said.

“Which has been a real mystery,” he said, since gas giants, such as Jupiter and WASP 107b, need massive cores to accumulate all that gas. These cores are also usually warm because otherwise, a cold core could force it to shrink naturally, reducing its size.


JWST enabled astronomers to take another look at WASP 107b, this time measuring the gases in its atmosphere to estimate its interior temperature.NASA

But, according to scientific models, the core of WASP 107b was smaller than it should be – measuring no more than 4.6 Earth masses, Sing said.

So, it is clear that astronomers were not seeing the whole picture.

Enter JWST: the most powerful telescope ever launched into space. With this tool, Sing and Welbanks discovered that previous assumptions about WASP 107b’s interior were wrong.

Subsurface examination

Transmission spectrum for WASP 107-bTransmission spectrum for WASP 107-b

This chart shows the various gases that make up WASP 107b’s atmosphere. When Sing and Welbanks measured methane, it was found that there was less than expected. That was the key to understanding his essence.NASA, ESA, CSA, Ralf Crawford (STScI) Science: D. Sing (JHU) and the NIRSpec GTO transit exoplanet team

To solve the mystery of WASP 107b, the Welbanks and Sing teams analyzed the composition of the exoplanet’s atmosphere with JWST.

Each team identified some of the usual suspects such as carbon dioxide, sulfur dioxide, and water vapor. But they were surprised to find an unusually low amount of methane.

Methane is unstable at high temperatures. But the surface temperature of WASP 107b was cold enough that it should contain more methane than observed by JWST.

The most plausible answer to this methane mystery was that hot gas from deep within the exoplanet was mixing vigorously with the cooler gas near the surface, according to Welbanks and Sing.

“With these new measurements, we’re able to essentially use methane as a thermometer into the interior, and we see that it’s much hotter than we expected,” said Sing.

Both teams published their separate studies in the peer-reviewed journal Nature.

illustration of the james webb space telescope with gold panels against a starry purple backgroundillustration of the james webb space telescope with gold panels against a starry purple background

JWST may not be able to peer directly into a planet’s interior, but it can gather information about its atmosphere to reveal what’s inside.NASA

Since the JWST observations showed that the core was hotter, it was probably much larger, which would explain WASP 107b’s large diameter. In fact, both Sing and Welbanks concluded that the core is much larger than the original estimates.

However, the core mass measurements by Welbanks and Sing differ. Although this discrepancy needs further investigation, the two studies are basically telling the same story, said Scott Gaudi, professor of astronomy at Ohio State University.

“The fact that this thing is puffy is mainly due to the high internal temperature,” said Gaudi, who was not involved in the research but is a former colleague and co-author of the Welbanks paper.

Collaboration is key

A collage of puffball superplanets compared to planets in our solar systemA collage of puffball superplanets compared to planets in our solar system

The results of Sing and Welbanks’ collaborative research could inform future studies of other supernovae, such as the Kepler 51 planets.NASA, ESA, and L. Hustak and J. Olmsted (STScI)

This clarified picture of WASP 107b’s interior doesn’t mean astronomers are done asking questions about this strange superpuff. One question that remains is how the core of this exoplanet got so hot in the first place.

“Exactly what is causing the high internal temperature is not clear,” said Gaudi. But Welbanks and Sing have a theory — a theory that Gaudi thinks might be right.

WASP 107b’s orbit around its host star is “eccentric,” meaning it is not perfectly circular. That eccentric orbit squeezes the planet from time to time, and “just like playing with silly putty in your hands and moving it around, it gets hot,” explained Welbanks.

That heat generated squeezing is called tidal heating. Gaudi thinks it’s a strong explanation for why WASP 107b’s core is much hotter than expected.

But Gaudi still has some questions about the mechanisms behind this tidal heating.

For example, for WASP 107b’s eccentric orbit to heat its core this much, the core would have to dissipate tidal heating very efficiently, Gaudi said.

Map of all known exoplanetsMap of all known exoplanets

NASA’s map of all 4,003 known exoplanets discovered in 2019. Each of these planets has its own unique characteristics, and scientists like Sing and Welbanks are helping us understand them.YSTEM Sounds (M. Russo, A. Santaguida); Details: NASA Exoplanet Archive

This means that every time the exoplanet is “squeezed” as it orbits its star, a lot of energy is pumped into the core. According to Gaudi, that also means that the orbit of the exoplanet should not remain eccentric for very long – eventually, it should become perfectly circular.

So why is the orbit of WASP 107b still eccentric? Did Sing and Wellbanks simply catch it at the right time, or is there something else driving the exoplanet’s odd orbit, like the pull of a neighboring planet?

Welbanks and Sing plan to investigate WASP 107b’s orbit, tidal heating, and other remaining questions.

But for Sing, Welbanks, and Gaudi, the most important lesson to be learned from this work is that collaboration succeeds.

“In the age of science where many things are not reproducible, it was very encouraging for his team to come up with the same thing immediately,” said Sing.

“Science gets better and better when you work together,” said Welbanks.

Read the original article on Business Insider

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