V1054 Ophiuchi

V1054 Ophiuchi, together with the star Gliese 643, is a nearby quintuple star system, located in the constellation Ophiuchus at a distance of 21.2 light-years. It consists of five stars, all of which are red dwarfs. The alternative designation of Wolf 630 forms the namesake of a moving group of stars that share a similar motion through space.

Overview

Hierarchy of orbits in the system

V1054 Ophiuchi/Gliese 643 is the nearest quintuple star system; the next nearest star systems with at least five stars are Xi Ursae Majoris at 28.5 light-years, Castor at 49.2 light-years, and GJ 2069 at 54.3 light-years. V1054 Ophiuchi and Xi Ursae Majoris are the only two quintuple star systems within 10 parsecs.
The system consists of three widely separated parts:

close triple subsystem V1054 Ophiuchi A-Bab
Gliese 643
V1054 Ophiuchi C

The brightest and most massive of these five stars is V1054 Ophiuchi A. The close binary subsystem V1054 Ophiuchi B is more massive than V1054 Ophiuchi A, however, its total visual magnitude is 0.1 mag fainter than V1054 Ophiuchi A's visual magnitude.
The total apparent magnitude of the V1054 Ophiuchi A-Bab triple subsystem is 9.02.
Despite V1054 Ophiuchi/Gliese 643 consisting of low-mass stars, the system's total mass, due to the large number of components, exceeds the Solar mass, about.

Distance

Currently, the most accurate distance estimate of V1054 Ophiuchi/Gliese 643 is a trigonometric parallax of Gliese 643 from Gaia DR3: mas, corresponding to a distance of pc, or ly.
Past V1054 Ophiuchi/Gliese 643 distance estimates
V1054 Ophiuchi A-Bab:

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
the Sun ">Woolley		156 ± 4	6.41 ± 0.17	20.9 ± 0.6
GJ, 3rd version		153.9 ± 2.6	6.50 ± 0.11	21.19 ± 0.36
YPC, 4th edition		154.8 ± 0.6	6.460 ± 0.025	21.07 ± 0.08
Hipparcos		174.23 ± 3.90	5.74 ± 0.13	18.7 ± 0.4
Soederhjelm		155.63 ± 1.81	6.43 ± 0.08	20.96 ± 0.25
Hipparcos2		161.41 ± 5.64	6.20 ± 0.22	20.21 ± 0.73

Gliese 643:

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
Woolley		169 ± 5	5.92 ± 0.18	19.3 ± 0.6
GJ, 3rd version		171.9 ± 7.3	5.82 ± 0.26	19.0 ± 0.8
YPC, 4th edition		169.8 ± 6.6	5.89 ± 0.24	19.2 ± 0.8
Hipparcos		153.96 ± 4.04	6.50 ± 0.18	21.2 ± 0.6
Hipparcos2		148.92 ± 4.00	6.72 ± 0.19	21.9 ± 0.6

V1054 Ophiuchi C :

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
CTIOPI 1.5 m	TSN 14	155.43 ± 1.33	6.43 ± 0.06	20.98 ± 0.18

Weighted mean distance

A weighted mean parallax was calculated by RECONS in 2012, considering YPC, Hipparcos and CTIOPI data. The value is mas, corresponding to a distance of pc, or ly. This predates Gaia astrometry of the system.

System

V1054 Ophiuchi A-Bab (inner triple subsystem)

V1054 Ophiuchi A-Bab is a close spectroscopic triple subsystem, consisting of the brighter component V1054 Ophiuchi A and the more massive binary subsystem V1054 Ophiuchi Bab, orbiting each other with a period of 627 days, or 1.72 years. V1054 Ophiuchi Bab components are orbiting each other with a period of 2.9655 days. Both outer and inner orbits are nearly circular and, probably, coplanar.
V1054 Ophiuchi A-Bab pair is also visually resolved.

Gliese 643

The projected separation of Gliese 643 from V1054 Ophiuchi A-Bab is 72 arcsec, corresponding at 21.05 light-years to 465 AU.

V1054 Ophiuchi C (vB 8)

vB 8 is the smallest, faintest, and most separated component of the V1054 Ophiuchi system. The projected separation of the red dwarf from the primary triple system is about 220 arcsec, corresponding at 21.05 light-years to 1420 a.u. Since it is only three times larger than the projected separation between Gliese 643 and V1054 Ophiuchi A-Bab, and such a small ratio should render the triple system dynamically unstable, it was suggested that the real separation of V1054 Ophiuchi C from V1054 Ophiuchi A-Bab is much larger, at least by a factor of two, i. e. at least 2840 a.u.
In 1984, the apparent detection of an infrared source near vB 8 suggested it had a low mass companion. The low mass of this candidate led to speculation that it may be a brown dwarf; the first such to be detected. This discovery was later found to be spurious, but it produced much interest in this class of astronomical object.