New Planet In Kepler-51 System – Discovered

Eddie Gonzales Jr. – MessageToEagle.com – An unusual planetary system with three known ultra-low density “super-puff” planets has at least one more planet, according to new research led by researchers from Penn State and Osaka University.

Illustration of the Kepler-51 system and its inner three planets, which have unusually low density. New observations from NASA’s James Webb Space Telescope suggest that at least one more planet is in the system. Credit: NASA, ESA, and L. Hustak, J. Olmsted, D. Player and F. Summers (STScI)

The research team set out to study Kepler-51d, the third planet in the system, with NASA’s James Webb Space Telescope (JWST) but almost missed their chance when the planet unexpectedly passed in front of its star two hours earlier than models predicted.

After scrutinizing new and archival data from a variety of space and Earth-based telescopes, the researchers found that the best explanation is the presence of a fourth planet, whose gravitational pull impacts the orbits of the other planets in the system.

“Super puff planets are very unusual in that they have very low mass and low density,” said Jessica Libby-Roberts, Center for Exoplanets and Habitable Worlds Postdoctoral Fellow at Penn State and co-first author of the paper. “The three previously known planets that orbit the star, Kepler-51, are about the size of Saturn but only a few times the mass of Earth, resulting in a density like cotton candy. We think they have tiny cores and huge atmospheres of hydrogen of helium, but how these strange planets formed and how their atmospheres haven’t been blown away by the intense radiation of their young star has remained a mystery. We planned to use JWST to study one of these planets to help answer these questions, but now we have to explain a fourth low-mass planet in the system!”

When a planet transits its star, it blocks some light, causing a slight decrease in brightness. This decrease reveals the planet’s size and characteristics. Planets transit as they orbit their star but may transit early or late due to gravitational pulls from other planets in the system.

These minor differences are known as transit timing variations and are built into astronomers’ models to allow them to accurately predict when planets will transit.

The researchers had no reason to doubt the three-planet model of the Kepler-51 system. They used it successfully to predict and observe the transit of Kepler-51b in May 2023 with the Apache Point Observatory telescope.

“We also tried to use the Penn State Davey Lab telescope to observe a transit of Kepler-51d in 2022, but some poorly timed clouds blocked our view right as the transit was predicted to start,” Libby-Roberts said. “It’s possible we could have learned something was off then, but we had no reason to suspect that Kepler-51d wouldn’t transit as expected when we planned to observe it with JWST.”

The team’s three-planet model predicted that Kepler-51d would transit around 2 a.m. EDT in June 2023, and the researchers prepared to observe the event with both JWST and APO.

“Thank goodness we started observing a few hours early to set a baseline, because 2 a.m. came, then 3, and we still hadn’t observed a change in the star’s brightness with APO,” Libby-Roberts said. “After frantically re-running our models and scrutinizing the data we discovered a slight dip in stellar brightness immediately when we started observing with APO, which ended up being the start of the transit — 2 hours early, which is well beyond the 15-minute window of uncertainty from our models!”

When the researchers analyzed the new APO and JWST data, they confirmed that they had captured the transit of Kepler-51d, albeit considerably earlier than expected.

“We were really puzzled by the early appearance of Kepler-51d, and no amount of fine-tuning the three-planet model could account for such a large discrepancy,” said Kento Masuda, associate professor of earth and space science at Osaka University and co-first author of the paper. “Only adding a fourth planet explained this difference. This marks the first planet discovered by transit timing variations using JWST.”

To explain the Kepler-51 system, the team analyzed transit data from NASA’s Kepler and TESS telescopes. They observed inner planets with Hubble and Palomar Observatory and used archival data from ground-based telescopes. Since Kepler-51e hasn’t been seen transiting, likely due to its position, extensive data was crucial for their models.

“We conducted what is called a ‘brute force’ search, testing out many different combinations of planet properties to find the four-planet model that explains all of the transit data gathered over the past 14 years,” Masuda said. “We found that the signal is best explained if Kepler-51e has a mass similar to the other three planets and follows a fairly circular orbit of about 264 days — something we would expect based on other planetary systems. Other possible solutions we found involve a more massive planet on a wider orbit, though we think these are less likely.”

Accounting for a fourth planet alters the expected masses of the system’s other planets, affecting inferred properties and formation theories. The inner three planets are slightly more massive but still classified as super puffs. However, it’s unclear if Kepler-51e is a super puff since researchers haven’t observed its transit to calculate its radius or density.

“Super puff planets are fairly rare, and when they do occur, they tend to be the only one in a planetary system,” Libby-Roberts said. “If trying to explain how three super puffs formed in one system wasn’t challenging enough, now we have to explain a fourth planet, whether it’s a super puff or not. And we can’t rule out additional planets in the system either.”

Because the researchers believe Kepler-51e has an orbit of 264 days, they said that additional observing time is needed to get a better picture of the impacts of its gravity — or that of additional planets — on the inner three planets in the system.

“Kepler-51e has an orbit slightly larger than Venus and is just inside the star’s habitable zone, so a lot more could be going on beyond that distance if we take the time to look,” Libby-Roberts said. “Continuing to look at transit timing variations might help us discover planets that are further away from their stars and might aid in our search for planets that could potentially support life.”

Researchers are analyzing more JWST data, potentially revealing details about Kepler-51d’s atmosphere. Studying the composition of the inner three planets may also enhance understanding of how ultra-low density super puff planets formed.

Source

Paper 

Written by Eddie Gonzales  Jr. – MessageToEagle.com Staff Writer