GJ 4256 b

GJ 4256 b was discovered in 2024 using the transit method. The star was observed in September of 2019 and 2022 using the Transiting Exoplanet Survey Satellite (TESS). It was also observed with the CARMENES instrument at the Calar Alto Observatory. If GJ 4156 had a companion star, that star could have produced false-positive transit signals. To remove the possibility of false-positives, the star was observed to look for any companion stars with Palomar/PHARO. There were no companion stars found.^[1][2]

After the detection of GJ 4256 b, there was a search for additional planets in the systems. A transit signal was uncovered designated TOI-6255.02. If it were a planet, it would have an orbit of 14.48 days. This signal was also reported on the ExoFOP website by a citizen scientist named Alton Spencer. However due to a lack of additional prominent signals and a substantial flux occurring in a nearby background star, the TOI-6255.02 signal was likely a false-positive.^[1]

The first is a two-layer interior model with an iron core that is surrounded by a silicate mantle. This would make the iron core mass fraction (CMF) be 0.45 ±0.32. The second is the SUPEREARTH model which is able to distinguish between the true iron mass fraction (Fe-CMF of 0.38 ± 0.15) which may be due to the silicate mantle containing iron while the iron core containing other elements. Results show that the simpler two-layered model seems to be more accurate.^[1]

The planet magnetically interacts with its star that is analogous to the interaction between Jupiter and one of its moons Io.^[1]

The planet orbits so close to the host star that it has nearly passed the roche limit. The expected tidal forces caused by the star would likely have deformed the planet pulling it into an triaxial ellipsoid (egg-like shape) with its long axis that is ∼10% longer than the short axis. It is possible that the tidal distortion may be significantly greater than what Love theory predicts with the long axis being 15% longer than the short axis.^[1][2]

It experiences tidal orbital decay and it is predicted that in around 400 million years, the planet will have passed the roche limit of parent star and be ripped apart and engulfed by the star. GJ 4256 is likely not in the process of disintegrating (see: catastrophically evaporating planets). Examples of disintegrating planets, all of which have orbital periods that are greater than GJ 4256, include KOI-2700 b, KIC 12557548 b, K2-22b and BD+05 4868Ab. Evidence for disintegration would be asymmetries in the transit data and debris material up to a kilometer in size would be detectable. However no evidence for disintegration has been observed.^[1]