45 Ophiuchi

This article is about d Ophiuchi and is not to be confused with δ Ophiuchi.

45 Ophiuchi is a single^[10] star in the equatorial constellation of Ophiuchus, along the southern border with Scorpius. It has the Bayer designation d Ophiuchi, while 45 Ophiuchi is the Flamsteed designation. In the past it had the designation Theta Telescopii.^[11] This object is visible to the naked eye as a faint, yellow-white hued star with an apparent visual magnitude of 4.28.^[1] It is located approximately 111.6 light years away from the Sun based on parallax.^[2] The star is drifting further from the Earth with a heliocentric radial velocity of +38 km/s.^[5]

45 Ophiuchi

Location of 45 Ophiuchi (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Ophiuchus[1]
Right ascension	17h 27m 21.27571s[2]
Declination	−29° 52′ 01.3262″[2]
Apparent magnitude (V)	4.28[1]
Characteristics
Spectral type	F5III-IV[3]
U−B color index	+0.11[4]
B−V color index	+0.40[4]
Astrometry
Radial velocity (Rv)	+38.00[5] km/s
Proper motion (μ)	RA: +17.08[2] mas/yr Dec.: −138.02[2] mas/yr
Parallax (π)	29.23±0.20 mas[2]
Distance	111.6 ± 0.8 ly (34.2 ± 0.2 pc)
Absolute magnitude (MV)	1.61[1]
Details
Mass	1.71[6] M☉
Radius	3.2[6] R☉
Luminosity	19.07[1] L☉
Surface gravity (log g)	3.67[6] cgs
Temperature	6,750[7] K
Metallicity [Fe/H]	+0.10[7] dex
Rotational velocity (v sin i)	65.4[8] km/s
Age	1.24±0.18[7] Gyr
Other designations
d Oph, 45 Oph, CD−29°13557, FK5 646, GC 23627, HD 157919, HIP 85423, HR 6492, SAO 185412[9]
Database references
SIMBAD	data

This object has a stellar classification of F5III-IV,^[3] matching an F-type star with a luminosity class displaying mixed traits of a subgiant and a giant star. It is 1.2^[7] billion years old with 1.7^[6] times the mass of the Sun and 3.2^[6] times the Sun's radius. The star is radiating 19^[1] times the luminosity of the Sun from its photosphere at an effective temperature of 6,750 K.^[7] It is spinning with a projected rotational velocity of 65 km/s.^[8]