HD 171819

HD 171819, also known as HR 6986 or rarely 22 G. Telescopii, is a solitary star^[14] located in the southern constellation Telescopium. It is faintly visible to the naked eye as a white-hued object with an apparent magnitude of 5.84.^[2] The object is located relatively close at a distance of 313 light years based on Gaia DR3 parallax measurements, but it is approaching the Solar System with a heliocentric radial velocity of −9 km/s.^[6] At its current distance, HD 171819's brightness is diminished by one-quarter of a magnitude due to interstellar dust^[15] and it has an absolute magnitude of +0.65.^[7]

HD 171819

Location of HD 171819 (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Telescopium
Right ascension	18h 39m 14.29289s[1]
Declination	−47° 54′ 35.1520″[1]
Apparent magnitude (V)	5.84±0.01[2]
Characteristics
Spectral type	A7 IV/V[3] or A3 V[4]
B−V color index	+0.23[5]
Astrometry
Radial velocity (Rv)	−9±4.3[6] km/s
Proper motion (μ)	RA: +25.426 mas/yr[1] Dec.: +13.951 mas/yr[1]
Parallax (π)	10.4348±0.1045 mas[1]
Distance	313 ± 3 ly (95.8 ± 1.0 pc)
Absolute magnitude (MV)	+0.65[7]
Details
Mass	1.73+0.37 −0.19[8] M☉
Radius	3.37±0.17[9] R☉
Luminosity	33.3±0.1[1] L☉
Surface gravity (log g)	3.60±0.08[8] cgs
Temperature	7,512[10] K
Metallicity [Fe/H]	−0.02[11] dex
Age	855[1] Myr
Other designations
22 G. Telescopii[12], CD−48°12644, CPD−48°9900, FK5 3482, GC 25474, HD 171819, HIP 91461, HR 6986, SAO 229165[13]
Database references
SIMBAD	data

HD 171819 has a stellar classification of A7 IV/V, indicating that the object is a late A-type star with the blended luminosity class of a main sequence star and subgiant.^[3] However, astronomer William Buscombe gave it a class of A3 V,^[4] instead making it an ordinary A-type main-sequence star. Evolutionary models give it an age of 855 million years and place it towards the end of its main-sequence life.^[1] At present it has 1.73 times the mass of the Sun^[8] and a slightly enlarged radius 3.37 times that of the Sun.^[9] It radiates 33.3 times the luminosity of the Sun^[1] from its photosphere at an effective temperature of 7,512 K.^[10] HD 171819 has a near solar metallicity at [Fe/H] = −0.02.^[11]