53 Aquarii

53 Aquarii (abbreviated 53 Aqr) is a binary star^[12] system in the equatorial constellation of Aquarius. 53 Aquarii is its Flamsteed designation though the star also bears the Bayer designation of f Aquarii. The combined apparent visual magnitude of the pair is a 5.56,^[2] making it just visible to the naked eye in dark suburban skies. Based upon an annual parallax shift of 49.50 milliarcseconds for the first component, this system is located at a distance of approximately 65 light-years (20 parsecs) from Earth.^[1]

53 Aquarii

Location of 53 Aquarii (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aquarius
Right ascension	22h 26m 34.2753s[1]
Declination	−16° 44′ 31.697″[1]
Apparent magnitude (V)	5.56[2] (6.35/6.57)[3]
Characteristics
Spectral type	G1 V + G5 V Fe–0.8 CH–1[4]
U−B color index	+0.09[2]
B−V color index	+0.61[2]
Astrometry
Radial velocity (Rv)	+2.1[5] km/s
Proper motion (μ)	RA: +200.59[1] mas/yr Dec.: +14.51[1] mas/yr
Parallax (π)	49.50±1.23 mas[1]
Distance	66 ± 2 ly (20.2 ± 0.5 pc)
Absolute magnitude (MV)	4.05[5] (4.94/4.87)[3]
Orbit[6]
Primary	53 Aqr A
Companion	53 Aqr B
Period (P)	3500 yr
Semi-major axis (a)	14.88″
Eccentricity (e)	0.90
Inclination (i)	44.13°
Longitude of the node (Ω)	294.55°
Periastron epoch (T)	B 2023
Argument of periastron (ω) (secondary)	151.40°
Details
53 Aqr A
Mass	1.01[7] M☉
Radius	1.11[8] R☉
Luminosity	1.39[8] L☉
Surface gravity (log g)	4.46[3] cgs
Temperature	5,922[3] K
Metallicity [Fe/H]	−0.10[3] dex
Rotational velocity (v sin i)	8[9] km/s
Age	0.18–0.37[10] Gyr
53 Aqr B
Mass	0.99[7] M☉
Surface gravity (log g)	4.44[3] cgs
Temperature	5,811[3] K
Metallicity [Fe/H]	−0.19[3] dex
Rotational velocity (v sin i)	9[9] km/s
Other designations
GJ 859, HIP 110778.[11]
53 Aqr A: BD−17 6521, HD 212698, HR 8545, LTT 9026, SAO 165078.
53 Aqr B: BD−17 6520, HD 212697, HR 8544, LTT 9025, SAO 165077.
Database references
SIMBAD	53 Aqr
	53 Aqr A
	53 Aqr B

This is a wide binary star system with a projected separation of 100 astronomical units; indicating that the two stars are at least this distance apart.^[8] The primary component is a solar-type main sequence star with a stellar classification of G1 V.^[4] It has about 99% of the Sun's mass, 111% of the Sun's radius, and shines with 139% of the luminosity of the Sun.^[8] This energy is being emitted from an outer envelope at an effective temperature of 5,922 K,^[3] giving it the golden hue of a G-type star.^[13] An examination of the primary component with the Spitzer Space Telescope failed to detect any infrared excess that might otherwise be an indication of a circumstellar debris disk.^[8]

The companion is a slightly cooler star with an effective temperature of 5,811 K.^[3] It has a stellar classification of G5 V Fe–0.8 CH–1,^[4] indicating it is a chemically peculiar G-type main sequence star showing an under-abundance of iron and the molecule CH in its spectrum. As of 2008, it has an angular separation of 1.325 arcseconds along a position angle of 30.9° from the primary.^[14]

This system is coeval with the Castor Moving Group of stars that share a common motion through space; hence it is a candidate member of that association. This suggests that the system is young; its estimated age is in the range of 180 to 370 million years, based upon the spectrum and X-ray luminosity, respectively.^[10]