18_Sextantis
18 Sextantis
K-type giant star in the constellation Sextans
18 Sextantis (HD 88333; HR 3996; 32 G. Sextantis), or simply 18 Sex, is a solitary star[15] located in the southern constellation Sextans. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.62.[2] Gaia DR3 parallax measurements imply a distance of 558 light-years[1] and it is slowly receding with a poorly constrained heliocentric radial velocity of approximately 0.2 km/s.[5] At its current distance, 18 Sex's brightness is diminished with an interstellar extinction of two-tenths of a magnitude[16] and it has an absolute magnitude of −0.16.[6]
18 Sex has a stellar classification of K2/3 III,[3] indicating that it is an evolved star with the characteristics of a K2 and K3 giant star. At present, it has exhausted hydrogen at its core and it has expanded to 27.3 times the radius of the Sun.[7] It radiates 222 times the luminosity of the Sun[8] from its enlarged photosphere at an effective temperature of 4,410 K.[10] Gaia DR3 models it to be a larger and brighter red giant branch star with a radius of 35.27 R☉ and a luminosity of 384 L☉.[1] 18 Sex is metal deficient with an iron abundance of [Fe/H] = −0.31 or 49% of the Sun's[11] and it spins too slowly for its projected rotational velocity to be measured accurately, having a velocity lower than 1.0 km/s.[12]