Rho Aquilae

Rho Aquilae, ρ Aquilae, is the Bayer designation for a star in the northern constellation of Delphinus. It has an apparent visual magnitude of 4.94^[2] and is bright enough to be seen with the naked eye in good conditions.

ρ Aquilae

Location of Rho Aquilae (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Delphinus
Right ascension	20h 14m 16.61886s[1]
Declination	+15° 11′ 51.3923″[1]
Apparent magnitude (V)	4.94[2]
Characteristics
Spectral type	A2 V[3]
U−B color index	+0.01[4]
B−V color index	+0.09[4]
Astrometry
Radial velocity (Rv)	−23.0[2] km/s
Proper motion (μ)	RA: +55.03[1] mas/yr Dec.: +58.14[1] mas/yr
Parallax (π)	21.75±0.26 mas[1]
Distance	150 ± 2 ly (46.0 ± 0.5 pc)
Absolute magnitude (MV)	+1.63[5]
Details
Mass	1.94±0.04[6] M☉
Radius	1.95[7] R☉
Luminosity	22[6] L☉
Surface gravity (log g)	4.2[7] cgs
Temperature	8,900±100[6] K
Metallicity [Fe/H]	−0.21[8] dex
Rotational velocity (v sin i)	180[9] km/s
Age	300±100[6] Myr
Other designations
Tso Ke, ρ Aql, 67 Aquilae, BD+14°4227, FK5 1526, HD 192425, HIP 99742, HR 7724, SAO 105878[10]
Database references
SIMBAD	data

Distance, proper motion and constellation

The annual parallax shift is 21.75 milliarcseconds,^[1] which corresponds to a distance of the star of around 150 light-years (46 parsecs) from Earth. Relatively high proper motion resulted in the star crossing the border from Aquila into Delphinus in 1992.^[11][12] Rho Aquilae is therefore a rare occurrence of a mismatch between current constellation and Bayer designation constellation. The star is in the low-northern constellation of Delphinus therefore at least seasonally visible to all but the high southern latitudes.

Chinese constellations and components

This star has the traditional name Tso Ke, from the Cantonese 左旗 jo keih meaning "the left flag". In Chinese, 左旗 (Zuǒ Qí in Mandarin), within the Ox, refers to an asterism consisting of this star, α, β, γ, δ, ζ, 11, 13, and 14 Sagittae stars of Sagitta to the west.^[13] Consequently, ρ Aquilae itself is known as 左旗九 (Zuǒ Qí jiǔ, English: the Ninth Star of Left Flag.)^[14]

Physical characteristics

Rho Aquilae is an A-type main sequence star with a stellar classification of A2 V.^[3] This star is about 400 million years old and it displays an excess emission of infrared radiation that may be explained by a circumstellar disk of dust.^[15][16]