The secondary component, named 58 Aquarii Ab, is a K-type dwarf, with around 70% of the Sun's size and an effective temperature around 4,540 K, separated by 2.3 astronomical units from Aa. It was initially uncovered via astrometry from the Hipparcos spacecraft, and later detected via interferometric observations by Idel Waisberg et al. This inner system will become a common envelope binary, when 58 Aquarii Aa expands in the red giant phase. Mass transfer between components is also expected to occur.[3]
The tertiary component, named 58 Aquarii B, is a widely-separated white dwarf, located at 9,940 astronomical units from the inner pair.[3]
^ abHouk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
^ abPaunzen, E.; et al. (February 2013), "A photometric study of chemically peculiar stars with the STEREO satellites - II. Non-magnetic chemically peculiar stars", Monthly Notices of the Royal Astronomical Society, 429 (1): 119–125, arXiv:1211.1535, Bibcode:2013MNRAS.429..119P, doi:10.1093/mnras/sts318, S2CID119231581.