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.[11]
Struve 2398 A is known to host one 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.[5]
Struve 2398 B may also host planets. In 2016, an Earth-mass planet candidate on a 2.7-day orbit was proposed around Struve 2398 B based on radial velocity observations, although this could not be confirmed as a periodic signal.[12]
The Struve 2398 A (Gliese 725 A) planetary system[5]
^Rojas-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.
^abcdCortés-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.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.
^Berdiñas, Z. M.; Amado, P. J.; Anglada-Escudé, G.; Rodríguez-López, C.; Barnes, J. (2016), "High-cadence spectroscopy of M dwarfs – I. Analysis of systematic effects in HARPS-N line profile measurements on the bright binary GJ 725A+B",Monthly Notices of the Royal Astronomical Society,459 (4):3551–3564,arXiv:1604.05312,Bibcode:2016MNRAS.459.3551B,doi:10.1093/mnras/stw906
