Rho Ophiuchi

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This article is about the star. For the dark cloud star forming region, see Rho Ophiuchi cloud complex.
Rho Ophiuchi
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ophiuchus
Right ascension 16h 25m 35.118s[1][2]
Declination −23° 26′ 49.81″
Apparent magnitude (V) 4.63[1][3]
Spectral type B2/B3V (ρ Oph A);[4] B2 V (ρ Oph B)[5][6]
Apparent magnitude (U) 4.30[1][3]
Apparent magnitude (B) 4.85[1][3]
Apparent magnitude (V) 4.63[1][3]
Apparent magnitude (R) 4.27[1][3]
Apparent magnitude (I) 3.96[1][3]
Apparent magnitude (J) 3.74[1][3]
Apparent magnitude (H) 3.56[1][3]
Apparent magnitude (K) 3.51[1][3]
U−B color index -0.55
B−V color index +0.23
Variable type  ??
Proper motion (μ) RA: -5.53[1][2] mas/yr
Dec.: -21.74 mas/yr
Parallax (π) 9.03[1][2] ± 0.90 mas
Distance 360 (ρ Oph AB)[2] ly
(111 (ρ Oph AB) pc)
Absolute magnitude (MV) -0.70
Period (P) 2,000[citation needed] yr
Semi-major axis (a) 344 AU[7]
Mass 9 / 8[citation needed] M
Luminosity 4,900 / 2,100[citation needed] L
Temperature 27,200[citation needed] K
Rotation +300[citation needed]
Other designations
Rho Ophiuchi, Rho Oph, ρ Ophiuchi, ρ Oph, 5 Ophiuchi, 5 Oph, HIP 80473, 2MASS J16253509-2326486

Rho Ophiuchi (ρ Ophiuchi) is a multiple star system in the constellation Ophiuchus.[1] It consists of at least two blue subgiants, ρ Oph A and ρ Oph B, both of which are of class B.[7] ρ Oph AB is a visual binary, and the sky-projected distance between ρ Oph A and ρ Oph B is 3.1" (or 344 AU at the 111 pc distance of ρ Oph AB).[7]

Two to three other blue subgiants, ρ Oph C and ρ Oph DE, are found to be related to the star system, with sky-projected distances to ρ Oph AB of ~ 17,000 and ~ 19,000 AU, respectively. ρ Oph C and ρ Oph D are also of class B.

The apparent brightness of the star system has been dimmed by about 2 magnitudes[citation needed], as a result of interstellar extinction, due to its location within the Ophiuchus cloud. The star system, ρ Oph AB, is located about 360 light years away.[2]