How many exoplanets are in the cosmos and what can they tell us about planetary formation and evolution? This is what a recent study published in The Astronomical Journal hopes to address as an international team of more than 50 researchers announced the discovery of Kepler-51e, which is the fourth planet residing in the Kepler-51 system. This discovery holds the potential to expand our knowledge of exoplanets, specifically regarding their formation and evolution, as Kepler-51e challenges previous notions about low-density exoplanets, also called “puff planets” or “Super-Puffs”.
“Super puff planets are very unusual in that they have very low mass and low density,” said Dr. Jessica Libby-Roberts, who is a Postdoctoral Scholar in the Department of Astronomy and Astrophysics at Penn State University and second author of the study. “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.”
For the discovery, the researchers used NASA’s powerful James Webb Space Telescope (JWST) using a method called transit timing variations, which are caused by other planets in the system tugging on each other, resulting in very slight changes in their orbits. For example, the team noticed that the third planet in the system, Kepler-51d, transited its star two hours earlier than anticipated, indicating the gravity of an unknown fourth planet was tugging on it.
“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 Dr. Kento Masuda, who is an associate professor of earth and space science at Osaka University and lead author of the study. “Only adding a fourth planet explained this difference. This marks the first planet discovered by transit timing variations using JWST.”
The researchers note the discovery of Kepler-51e challenges previous notions about “Super-puff” exoplanets, which are large exoplanets with low densities, meaning they have very large atmospheres. However, the team has yet to calculate Kepler-51e’s radius or density since they haven’t observed it yet. What they do know is that it has an orbital period of approximately 264 days, which is slightly longer than Venus with an orbital period of 225 days.
“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,” said Dr. Libby-Roberts. “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.”
What new discoveries about Kepler-51 will astronomers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
Sources: The Astronomical Journal, Wikipedia, EurekAlert!
Featured Image: Artist's illustration of the Kepler-51 system. (Credit: NASA, ESA, and L. Hustak, J. Olmsted, D. Player and F. Summers (STScI))