New planet in Kepler-51 system discovered using James Webb Space Telescope

The discovery of the new planet is detailed in a paper published Dec. 3 in the journal Science astronomical magazine.

“Superinflated planets are very unusual because they have very low masses and very low densities,” said Jessica Libby, a postdoctoral researcher at Penn State’s Exoplanet Center and Habitable Worlds and co-first author of the paper. Roberts said. “The three previously known planets orbiting the star Kepler 51 are about the size of Saturn but only a few times the mass of Earth, making them as dense as marshmallows. We think they have tiny cores and huge hydrogen atmospheres But how these strange planets formed, and how their atmospheres were not blown away by the intense radiation of young stars, remains a mystery. Explaining the fourth low-mass planet in the system!

As seen from Earth, when a planet passes in front of or transits its star, it blocks some of the star’s light, causing the star to dip slightly in brightness. The duration and amount of this reduction provide clues to the planet’s size and other characteristics. Planets transit as they complete their orbits around their stars, but sometimes they transit a few minutes earlier or later because the gravity of other planets in the system pulls on them. These tiny differences are called transit time variations and are incorporated into astronomers’ models so that they can accurately predict when planets transit.

The researchers say they have no reason to believe the three-planet model of the Kepler 51 system is inaccurate, and they successfully used the model to predict the May 2023 transit time of Kepler 51b in conjunction with the Apache Point Observatory. The follow-up follow-up (APO) telescope carried out observations as planned.

“We also attempted to observe the 2022 transit of Kepler-51d using the Penn State Davy Laboratory telescope, but some untimely clouds blocked our view when the transit was expected to begin,” Libby-Roberts said. We may have known something was wrong at the time, but when we planned to observe Kepler-51d with JWST, we had no reason to doubt that it wouldn’t transit as expected.”

The team’s three-planet model predicts that Kepler 51d will transit the sun at approximately 2 a.m. ET in June 2023, and the researchers are preparing to observe this event with JWST and APO.

“Thankfully, we started observing a few hours early to set a baseline, because 2 a.m. came, and then 3 a.m., and we still didn’t see a change in the star’s brightness through APO,” Libby-Roberts said. “After frantically re-running our model and double-checking the data, when we started observing with APO we immediately saw a slight decrease in star brightness, ultimately causing the transit to begin – 2 hours ahead of schedule, which is well beyond 15 points – There is a tiny window of uncertainty in our model!

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

“We are very puzzled by the early appearance of Kepler 51d, and no amount of fine-tuning of the three-planet model can explain such a large difference,” said Kento Masuda, an associate professor in the Department of Earth and Space Sciences at Osaka University, according to the paper. Co-first author. “Only the addition of a fourth planet could explain the difference. This marks the first planet discovered using JWST through changes in transit times.”

To help explain what’s happening in the Kepler-51 system, the team revisited previous transit data from NASA’s Kepler Space Telescope and NASA’s Transiting Exoplanet Survey Satellite (TESS). They also made new observations of the system’s inner planets using the Hubble Space Telescope and Caltech’s Palomar Observatory telescope, and obtained archival data from several ground-based telescopes. Since the new planet Kepler-51e has yet to be observed in transit—perhaps because it likely won’t pass within line of sight between its star and Earth—the researchers noted how important it is to get as much data as possible. of new models.

“We conducted a so-called ‘brute force’ search, testing many different combinations of planetary properties to find a four-planet model that could explain all the transit data collected over the past 14 years,” Masuda said. “We found that if Kepler The signal is best explained by the fact that 51e has a mass similar to the other three planets and follows a fairly circular orbit of about 264 days – what we would expect based on other planetary systems.

Taking into account a fourth planet and adjusting the model also changes the expected masses of the other planets in the system. This could affect other inferred properties of these planets and reveal how they might have formed, the researchers said. Although the three inner planets are slightly more massive than previously thought, they are still classified as superpuffs. However, it’s unclear whether Kepler-51e is also a super-inflated planet because researchers have not yet observed a transit of Kepler-51e and therefore cannot calculate its radius or density.

“Superbulge planets are quite rare, and when they do appear, they are often the only ones in a planetary system,” Libby-Roberts said. “If trying to explain how three superbubbles formed in one system wasn’t challenging enough, sex, then we now have to account for the fourth planet, whether it’s a superbubble or not, and we can’t rule out the existence of other planets in the system.

Because the researchers believe Kepler-51e has an orbital period of 264 days, additional observation time is needed to better understand the impact of its gravity (or the gravity of other planets) on the three planets in the system.

“Kepler 51e has an orbit slightly larger than Venus and is within the star’s habitable zone, so if we take the time to observe, there could be a lot more going on beyond this distance,” Libby-Roberts said. “Continue Studying changes in transit times may help us discover planets farther from their stars and may aid our search for planets that might support life.”

Researchers are currently analyzing the remaining JWST data, which could provide information about Kepler 51d’s atmosphere. Studying the composition and other exuberances of the three inner planets could also improve understanding of how unusual ultra-low-density super-pulverized planets form, the researchers said.

In addition to Libby-Roberts and Masuda, who lead the Kepler-51d team, the international research team includes John Livingston of the National Astronomical Observatory of Japan, who coordinated much of the ground-based follow-up work; a number of ground-based observers; the Kepler-51b team; and Palomar team.

NASA supported this research through grants from JWST and the Hubble Space Telescope. Computations for this study were performed on the advanced networking infrastructure of Penn State’s Institute for Computational and Data Sciences.