Psi Scorpii

Psi Scorpii, which is Latinized from ψ Scorpii, is a binary star in the zodiac constellation of Scorpius. It is white in hue and has an apparent visual magnitude of 4.94,^[2] which is bright enough to be faintly visible to the naked eye. Based upon parallax measurements,^[1] it is located at a distance of around 162 light years from the Sun. The system is drifting closer to the Sun with a radial velocity of −5 km/s.^[4]

ψ Scorpii

Observation data Epoch J2000      Equinox J2000
Constellation	Scorpius
Right ascension	16h 12m 00.01043s[1]
Declination	−10° 03′ 50.8353″[1]
Apparent magnitude (V)	4.94[2]
Characteristics
Spectral type	A1 V[3]
U−B color index	+0.11[2]
B−V color index	+0.09[2]
Astrometry
Radial velocity (Rv)	−5.10[4] km/s
Proper motion (μ)	RA: −18.000[1] mas/yr Dec.: −36.188[1] mas/yr
Parallax (π)	20.1801±0.2617 mas[1]
Distance	162 ± 2 ly (49.6 ± 0.6 pc)
Absolute magnitude (MV)	+1.55[5]
Orbit[6]
Period (P)	10 years
Semi-major axis (a)	6.4 au
Details[6]
ψ Sco A
Mass	1.95 M☉
Radius	2.1 R☉
Luminosity	18.6[7] L☉
Surface gravity (log g)	4.134±0.071[8] cgs
Temperature	8,350 K
Rotational velocity (v sin i)	42.3±0.6[9] km/s
Age	630 Myr
ψ Sco B
Mass	0.64 M☉
Radius	0.60 R☉
Temperature	4,200 K
Age	630 Myr
Other designations
ψ Sco, 15 Scorpii, BD−09°4324, FK5 3280, GC 21780, HD 145570, HIP 79375, HR 6031, SAO 141022[10]
Database references
SIMBAD	data

Characteristics

Data collected during the Hipparcos mission suggested it is an astrometric binary.^[11] The companion was directly detected in 2025, with the GRAVITY instrument at VLTI. The astrometric data is consistent with an orbital period of 10 years, suggesting a separation of 3.4 astronomical units.^[6]

The primary component is an A-type main sequence star with a stellar classification of A1 V;^[3] a class of star that is still fusing hydrogen at its core. It has around 1.95 the mass and 2.1 times the radius of the Sun,^[6] and is shining with 18.6 times the Sun's luminosity.^[7] The effective temperature of the star's outer atmosphere is 8,350 K. Psi Scorpii A is around 630 million years old^[6] and is spinning with a projected rotational velocity of 42.3 km/s.^[12]

The secondary is has around 0.64 times the mass, 0.6 times the radius and a temperature of 4,200 K. It is 6.7 magnitudes fainter than the primary.^[6]