Kepler-51 is a 500-million-year-old G-type star that hosts four low-density planets. new paper Published in astronomy magazine.
This diagram shows the Kepler-51 planetary system. Image credit: NASA / ESA / L. Hustak, J. Olmsted, D. Player & F. Summers, STScI.
Kepler-51 It is located approximately 2,615 light years away in the constellation Cygnus.
The star, also known as KOI-620, was already known to host three Saturn-sized “superpuff” exoplanets: Kepler-51b, c, and d.
First discovered by NASA's Kepler Space Telescope in 2012, these worlds have orbital period ratios close to 1:2:3 (45, 85, and 130 days, respectively).
It is several times more massive than Earth and has a hydrogen/helium atmosphere.
“Superpuff planets are very unusual in that they have very low masses and very low densities,” says Penn State astronomer Jessica Libby Roberts.
“The three planets known so far orbiting the star Kepler-51 are about the same size as Saturn, but only a few times the mass of Earth, making them as dense as cotton candy. ”
“We think they have small cores and huge atmospheres of helium hydrogen, but we don't know how these strange planets formed and how their atmospheres developed. It remains a mystery why the star was not blown away by the intense radiation of the young star.
“We had planned to use Webb to study one of these planets to answer these questions, but now we have to describe the fourth, low-mass planet in the system.”
To examine evidence of Kepler-51e, the fourth planet in the system, astronomers conducted extensive passes over 14 years from a variety of facilities, including the Webb, Apache Point Observatory telescopes, and Penn State Davey Laboratory telescopes. We utilized a timing dataset.
“We conducted a so-called 'brute force' search, testing different combinations of planet properties to find a four-planet model that explains all transit data collected over the past 14 years.” said Kento Masuda, an astronomer at Osaka University.
“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. That's to be expected.”
“Other possible solutions we've found include larger planets in wider orbits, but we think that's unlikely.”
It is unclear whether Kepler-51e is also a superpuff planet, as researchers have not observed Kepler-51e transiting the Sun and therefore cannot calculate its radius or density.
According to the team, a wide range of demographics (
“Superpuff planets are fairly rare, and when they do occur, they tend to be unique in planetary systems,” said Penn State astronomer Jessica Libby Roberts.
“If explaining how three superpuffs formed in one star system wasn't enough of a challenge, now we have to explain a fourth planet, whether it's a superpuff or not. And we can't rule out the possibility that there are more planets in this system.”
“Kepler-51e's orbit is slightly larger than Venus and just inside the star's habitable zone, so there could be a lot more going on beyond that distance if we take the time to look.”
“Continuing to observe variations in transit timing could help us discover planets further away from their stars, which could aid in the search for planets that may harbor life.”
_____
Kento Masuda others. 2024. The fourth planet in the Kepler-51 system revealed by fluctuations in transit timing. A.J. 168, 294; doi: 10.3847/1538-3881/ad83d3
Source: www.sci.news
