V1054 Ophiuchi, together with the star Gliese 643, is a nearby quintuple star system, in the constellation Ophiuchus at a distance of 21.19

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s. It consists of five stars, all of which are

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

s. The alternative designation of Wolf 630 forms the namesake of a

moving group In astronomy, stellar kinematics is the Observational astronomy, observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar Velocity, velocities in the Milky W ...

of stars that share a similar motion through space.

Overview

V1054 Ophiuchi/Gliese 643 has the largest number of stars of all star systems located within 10 pc from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. It is also the nearest quintuple star system (the next nearest star systems with at least five stars are GJ 2069 (quintuple) at 41.8 light-years, and Castor (sextuple) at 51.6 light-years), and the only quintuple star system within 10 pc.RECONS CENSUS OF OBJECTS NEARER THAN 10 PARSECS
/ref> The system consists of three widely separated parts: *close triple subsystem V1054 Ophiuchi A-Bab (including very close binary subsystem V1054 Ophiuchi Bab) *Gliese 643 *V1054 Ophiuchi C (vB 8) Hierarchy of the system: 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 The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

, (it is about ).

Distance

Currently, the most accurate distance estimate of V1054 Ophiuchi/Gliese 643 (apart from weighted mean distance, see below) is a

trigonometric parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to perspective (graphica ...

of V1054 Ophiuchi AB from

Gaia EDR3 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

, published in 2020:

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, corresponding to a distance of pc, or ly. Past V1054 Ophiuchi/Gliese 643 distance estimates V1054 Ophiuchi A-Bab: Gliese 643: V1054 Ophiuchi C (vB 8):

Weighted mean distance

Weighted mean The weighted arithmetic mean is similar to an ordinary arithmetic mean (the most common type of average), except that instead of each of the data points contributing equally to the final average, some data points contribute more than others. The ...

parallax,DENSE Project. 25 pc White Dwarf Sample
(see formulae below) considering YPC (V1054 Ophiuchi A-Bab and Gliese 643), Hipparcos (Soederhjelm — V1054 Ophiuchi A-Bab and van Leeuwen — Gliese 643) and CTIOPI (V1054 Ophiuchi C) data, is 154.96 ± 0.52 mas,
/ref> corresponding to a distance 6.453 ± 0.022 pc, or 21.05 ± 0.07 ly.

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 (in keeping with a general tendency of close triple systems). V1054 Ophiuchi A-Bab pair is also visually resolved (for nearly 50 years it was the shortest-period resolved by visual means binary, since its binarity was discovered by G. P. Kuiper in 1934), whereas V1054 Ophiuchi Ba-Bb pair is still unresolved).At least it was not resolved by 2001.

Distant components

Gliese 643

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

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 Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...

; 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.

Notes

References

{{DEFAULTSORT:V1054 Ophiuchi Ophiuchus (constellation) 5 M-type main-sequence stars 0644 Ophiuchi, V1054 152751 082817 Durchmusterung objects