Struve 2398 (Gliese 725) is abinary star system in the northern constellation ofDraco. Struve 2398 is star number 2398 in theStruve Double Star Catalog of Russian-German astronomerFriedrich Georg Wilhelm von Struve. The astronomer's surname, and hence the star identifier, is sometimes indicated by a Greek sigma, Σ; hence, this system can be listed with the identifier Σ 2398. Although the components are too faint to be viewed with the naked eye, this star system is among theclosest to the Sun.Parallax measurements by theGaia spacecraft give them an estimated distance of 11.5light-years (3.5parsecs) away.
The pair has a relatively highproper motion of 2.2 arc seconds per year. The system is on an orbit through theMilky Way that has an eccentricity of 0.05, carrying them as close as 8 kpc and as far as 9 kpc from theGalactic Center. The plane of their galactic orbit carries them as far as 463−489 pc away from thegalactic plane.[16]
Both stars of the Struve 2398 system are known to host planets.
Struve 2398 A has one known planet, a likelysuper-Earth discovered in 2024 using theradial velocity method. This planet has aminimum mass 2.8 times that of Earth, and has a close orbit with a period of 11 days; it is too close to its star to be in thehabitable zone.TESS observations show that the planet likely does nottransit its host star.[11]
Struve 2398 B also hosts one known planet, asuper-Earth orbiting within thehabitable zone, circling its host star every 37.9 days. An additional planet with an orbital period of 4.765 days is suspected. Both were detected using theradial velocity method and announced in 2025.[14] Other planetary candidates had previously been proposed around star B, but were not confirmed.[17]
The Struve 2398 A (Gliese 725 A) planetary system[11]
^abRojas-Ayala, Bárbara; et al. (April 2012). "Metallicity and Temperature Indicators in M Dwarf K-band Spectra: Testing New and Updated Calibrations with Observations of 133 Solar Neighborhood M Dwarfs".The Astrophysical Journal.748 (2): 93.arXiv:1112.4567.Bibcode:2012ApJ...748...93R.doi:10.1088/0004-637X/748/2/93.S2CID41902340. See Table 3.
^abCortés-Contreras, M.; Caballero, J. A.; Montes, D.; Cardona-Guillén, C.; Béjar, V. J. S.; Cifuentes, C.; Tabernero, H. M.; Zapatero Osorio, M. R.; Amado, P. J.; Jeffers, S. V.; Lafarga, M.; Lodieu, N.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Schöfer, P.; Schweitzer, A.; Seifert, W. (2024). "CARMENES input catalogue of M dwarfs VIII. Kinematics in the solar neighbourhood".Astronomy and Astrophysics.692.arXiv:2411.06825.Bibcode:2024A&A...692A.206C.doi:10.1051/0004-6361/202451585.
^abcdMyers, J. R.; Sande, C. B.; Miller, A. C.; Warren, W. H.; Tracewell, D. A. (2015). "VizieR Online Data Catalog: SKY2000 Master Catalog, Version 5 (Myers+ 2006)".Vizier Online Data Catalog.Bibcode:2015yCat.5145....0M.
^Pettersen, B. R.; Griffin, R. F. (1980). "Non-emission-line flare stars".The Observatory.100: 198.Bibcode:1980Obs...100..198P.
^abcdefghijCortés-Zuleta, P.; Boisse, I.; Ould-Elhkim, M.; Wilson, T. G.; Larue, P.; Carmona, A.; Delfosse, X.; Donati, J.-F.; Forveille, T.; Moutou, C.; Cameron, A. Collier; Artigau, É; Acuña, L.; Altinier, L.; Astudillo-Defru, N. (2025-01-01). "GI 725A b: A potential super-Earth detected with SOPHIE and SPIRou in an M dwarf binary system at 3.5 pc".Astronomy & Astrophysics.693: A164.arXiv:2411.09506.Bibcode:2025A&A...693A.164C.doi:10.1051/0004-6361/202451646.ISSN0004-6361.
^Allen, C.; Herrera, M. A. (1998). "The galactic orbits of nearby UV Ceti stars".Revista Mexicana de Astronomía y Astrofísica.34:37–46.Bibcode:1998RMxAA..34...37A.
