In 2016, the K2 Kepler mission discovered five planets around HIP 41378, with sizes ranging from 2 times the size of Earth to the size of Jupiter, out to about 1AU for the outermost planet.[9] The semi-major axes were not known until K2 Haute-Provence Observatory radial velocity data was obtained in 2019. Also, a sixth non-transiting planet, HIP 41378 g, was discovered, along with speculation that additional planets may exist between HIP 41378 g and HIP 41378 d. The planet HIP 41378 f was also found to likely have optically-thick rings or a highly extended atmosphere.[10][11] In 2026, radial velocity evidence for a seventh planet, named HIP 41378 h, with an orbital period of 2,600 days was found. However, it remains uncertain if the variations are caused by a planet or a magnetic cycle.[12]
The stellar rotation of HIP 41378 appears to be misaligned relative to the orbit of HIP 41378 f, and thus likely the other planets' orbits as well.[7]
↑Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
↑Hill, Sarah J.; Schilt, Jan (1952). "Photographic magnitudes of 55700 stars in the zones 10 deg to 20 deg and 30 deg to 50 deg". Contributions from the Rutherford Observatory of Columbia University New York. 32: 1. Bibcode:1952CoRut..32....1H.
↑Santerne, A.; Malavolta, L.; Kosiarek, M. R.; Dai, F.; Dressing, C. D.; Dumusque, X.; Hara, N. C.; Lopez, T. A.; Mortier, A.; Vanderburg, A.; Adibekyan, V.; Armstrong, D. J.; Barrado, D.; Barros, S. C. C.; Bayliss, D.; Berardo, D.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Buchhave, L. A.; Butler, R. P.; Collier Cameron, A.; Cosentino, R.; Crane, J. D.; Crossfield, I. J. M.; Damasso, M.; Deleuil, M. R.; Delgado Mena, E.; etal. (2019). "An extremely low-density and temperate giant exoplanet". arXiv:1911.07355 [astro-ph.EP].
