Webb observations uncover new planet in Kepler-51 ‘super-puff’ system

An uncommon planetary system with three identified ultra-low density “super-puff” planets has at the very least yet one more planet, in line with new analysis led by researchers from Penn State and Osaka University.

The analysis crew got down to research Kepler-51d, the third planet within the system, with NASA’s James Webb Space Telescope (JWST) however virtually missed their probability when the planet unexpectedly handed in entrance of its star two hours sooner than fashions predicted.

After scrutinizing new and archival information from quite a lot of area and Earth-based telescopes, the researchers discovered that one of the best rationalization is the presence of a fourth planet, whose gravitational pull impacts the orbits of the opposite planets within the system.

The new planet’s discovery is detailed in a paper showing in The Astronomical Journal.

“Super puff planets are very uncommon in that they’ve very low mass and low density,” stated Jessica Libby-Roberts, Center for Exoplanets and Habitable Worlds Postdoctoral Fellow at Penn State and co-first creator of the paper.

“The three beforehand identified planets that orbit the star Kepler-51 are concerning the dimension of Saturn however only some occasions the mass of Earth, leading to a density like cotton sweet. We suppose they’ve tiny cores and large atmospheres of hydrogen and helium, however how these unusual planets shaped and the way their atmospheres have not been blown away by the extreme radiation of their younger star has remained a thriller. We deliberate to make use of JWST to review one among these planets to assist reply these questions, however now now we have to clarify a fourth low-mass planet within the system.”

When a planet passes in entrance of—or transits—its star when considered from Earth, it blocks among the star’s gentle, inflicting a slight lower within the star’s brightness. The period and quantity of that lower offers clues to the planet’s dimension and different traits.

Planets transit after they full an orbit round their star, however typically they transit a couple of minutes early or late as a result of the gravity from different planets within the system tugs on them. These minor variations are generally known as transit timing variations and are constructed into astronomers’ fashions to permit them to precisely predict when planets will transit.

The researchers stated that they had no purpose to imagine the three-planet mannequin of the Kepler-51 system was inaccurate, they usually efficiently used the mannequin to foretell the transit time of Kepler-51b in May 2023 and followed-up with the Apache Point Observatory (APO) telescope to look at it on schedule.

“We additionally tried to make use of the Penn State Davey Lab telescope to look at a transit of Kepler-51d in 2022, however some poorly timed clouds blocked our view proper because the transit was predicted to begin,” Libby-Roberts stated. “It’s potential we may have discovered one thing was off then, however we had no purpose to suspect that Kepler-51d would not transit as anticipated once we deliberate to look at it with JWST.”

The crew’s three-planet mannequin predicted that Kepler-51d would transit round 2 a.m. EDT in June 2023, and the researchers ready to look at the occasion with each JWST and APO.

“Thank goodness we began observing a number of hours early to set a baseline, as a result of 2 a.m. got here, then 3, and we nonetheless hadn’t noticed a change within the star’s brightness with APO,” Libby-Roberts stated. “After frantically re-running our fashions and scrutinizing the information, we found a slight dip in stellar brightness instantly once we began observing with APO, which ended up being the beginning of the transit—2 hours early, which is effectively past the 15-minute window of uncertainty from our fashions.”

When the researchers analyzed the brand new APO and JWST information, they confirmed that that they had captured the transit of Kepler-51d, albeit significantly sooner than anticipated.

“We had been actually puzzled by the early look of Kepler-51d, and no quantity of fine-tuning the three-planet mannequin may account for such a big discrepancy,” stated Kento Masuda, affiliate professor of earth and area science at Osaka University and co-first creator of the paper. “Only including a fourth planet defined this distinction. This marks the primary planet found by transit timing variations utilizing JWST.”

To assist clarify what is going on within the Kepler-51 system, the analysis crew revisited earlier transit information from NASA’s Kepler area telescope and NASA’s Transiting Exoplanet Survey Satellite (TESS). They additionally made new observations of the internal planets within the system, together with with the Hubble Space Telescope and the California Institute of Technology’s Palomar Observatory telescope, and obtained archival information from a number of ground-based telescopes.

Because the brand new planet, Kepler-51e, has not but been noticed transiting—maybe as a result of it could not cross within the line of sight between its star and Earth—the researchers famous how necessary it was to acquire as a lot information as potential to assist their new fashions.

“We carried out what is known as a ‘brute pressure’ search, testing out many alternative combos of planet properties to seek out the four-planet mannequin that explains the entire transit information gathered over the previous 14 years,” Masuda stated.

“We discovered that the sign is greatest defined if Kepler-51e has a mass much like the opposite three planets and follows a reasonably round orbit of about 264 days—one thing we’d anticipate based mostly on different planetary techniques. Other potential options we discovered contain a extra huge planet on a wider orbit, although we expect these are much less doubtless.”

Accounting for a fourth planet and adjusting the fashions additionally modifications the anticipated lots of the opposite planets within the system. According to the researchers, this impacts different inferred properties about these planets and informs how they could have shaped. Although the internal three planets are barely extra huge than beforehand thought, they’re nonetheless categorised as tremendous puffs. However, it’s unclear if Kepler-51e can also be a brilliant puff planet, as a result of the researchers haven’t noticed a transit of Kepler-51e and subsequently can’t calculate its radius or density.

“Super puff planets are pretty uncommon, and after they do happen, they are typically the one ones in a planetary system,” Libby-Roberts stated. “If making an attempt to clarify how three tremendous puffs shaped in a single system wasn’t difficult sufficient, now now we have to clarify a fourth planet, whether or not it is a tremendous puff or not. And we won’t rule out extra planets within the system both.”

Because the researchers imagine Kepler-51e has an orbit of 264 days, they stated that extra observing time is required to get a greater image of the impacts of its gravity—or that of extra planets—on the three internal planets within the system.

“Kepler-51e has an orbit barely bigger than Venus and is simply contained in the star’s liveable zone, so much more might be occurring past that distance if we take the time to look,” Libby-Roberts stated. “Continuing to take a look at transit timing variations would possibly assist us uncover planets which are additional away from their stars and would possibly assist in our seek for planets that might probably assist life.”

The researchers are at the moment analyzing the remainder of the JWST information, which may present details about the ambiance of Kepler-51d. Studying the composition and different properties of the three internal planets may additionally enhance understanding of how the weird ultra-low-density tremendous puff planets shaped, the researchers stated.

In addition to Libby-Roberts and Masuda, who led the Kepler-51d crew, the worldwide analysis crew contains John Livingston on the National Astronomical Observatory of Japan, who coordinated a lot of the ground-based follow-ups; many ground-based observers; the Kepler-51b crew; and the Palomar crew.