HD 169904

HD 169904 (HR 6912; 35 G. Octantis) is a solitary star located in the southern circumpolar constellation Octans. It has an apparent magnitude of 6.26,^[2] placing it near the limit for naked eye visibility, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 482 light-years^[1] and it is currently drifting closer with a somewhat constrained radial velocity of −6.0 km/s.^[7] At its current distance, HD 169904's brightness is diminished by 0.24 magnitudes due to interstellar extinction^[16] and it has an absolute magnitude of +0.19.^[8]

HD 169904

Location of HD 204904 on the map (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	18h 42m 14.42015s[1]
Declination	−81° 48′ 29.2064″[1]
Apparent magnitude (V)	6.26±0.01[2]
Characteristics
Evolutionary stage	main sequence star[3]
Spectral type	B8 V[4]
U−B color index	−0.37[5]
B−V color index	−0.13[5]
Variable type	suspected[6]
Astrometry
Radial velocity (Rv)	−6.0±4.3[7] km/s
Proper motion (μ)	RA: +13.838 mas/yr[1] Dec.: −16.605 mas/yr[1]
Parallax (π)	6.7598±0.0413 mas[1]
Distance	482 ± 3 ly (147.9 ± 0.9 pc)
Absolute magnitude (MV)	+0.19[8]
Details
Mass	3.25±0.06[3] M☉
Radius	2.42±0.12[9] R☉
Luminosity	141+14 −13[3] L☉
Surface gravity (log g)	4.20[10] cgs
Temperature	13,622[11] K
Metallicity [Fe/H]	−0.18[12] dex
Rotational velocity (v sin i)	123[13] km/s
Other designations
35 G. Octantis[14], NSV 24510, CD−81°693, CPD−81°813, GC 25366, HD 169904, HIP 91723, HR 6912, SAO 258804, TIC 351920521[15]
Database references
SIMBAD	data

HD 169904 has a stellar classification of B8 V,^[4] indicating that it is an ordinary B-type main-sequence star that is generating energy via hydrogen fusion at its core. It has 3.25 times the mass of the Sun^[3] and 2.42 times the radius of the Sun.^[9] It radiates 141 times the luminosity of the Sun^[3] from its photosphere at an effective temperature of 13,622 K,^[11] giving it a blue-white hue when viewed in the night sky. HD 169904 is metal deficient with an iron abundance of [Fe/H] = −0.18 or 66.1% of the Sun's,^[12] and it spins rapidly with a projected rotational velocity of 123 km/s.^[13] HD 169904 is estimated to have completed 47.5% of its main sequence lifetime.^[3]

The object was listed as a suspected variable star based on photometric observations,^[6] but subsequent observations have not confirmed this.^[17]