12 Oph
ILLUSTRATION FROM MEASURED TEMPERATURE · 5110 K · 0.407 L☉ · VARIABLE, MAG 5.76–5.78 · TIMING NOT TO SCALE
OVERVIEW
] STAR12 Oph is a in the constellation Ophiuchus, 31.80 from Earth, shining at apparent magnitude 5.77 (). It is catalogued as Gl 631, HD 149661 and HIP 81300, among 6 designations in total.
- WHAT IT IS
- Orange dwarf
- HOW FAR
- 31.80
- HOW BRIGHT (V)
The light arriving now left it that long ago.
Bright enough for the naked eye, under a sky dark enough.
THE MODEL
] CATALOGUED RADIUSCALCULATED · NOT AN OBSERVATION · CATALOGUED RADIUS · MEASURED TEMPERATURE · 5110 K · 0.407 L☉ · VARIABLE, MAG 5.76–5.78
Drawn from the catalogued radius and from the same properties the picture at the top of this page uses, at the distance a flight to it would stop. Drag it, or use the arrow keys, to look from another direction. The stars behind are the 498,631 this catalogue holds real distances for, at their real positions and drawn from where the camera actually is — so the constellations are wrong, and that is the point. This is the sky from there, not the sky from here.
OBSERVING
] FROM WHERE YOU AREWhat it takes to see 12 Oph for yourself. Everything in this part of the page is worked out for a real horizon, a real night and the equipment you say you have.
Say where you are, and this line says when 12 Oph is worth going out for.
THROUGH AN EYEPIECE
] 150 MM TELESCOPE · 25 MM EYEPIECEBright enough to see with your eyes alone, once you are away from town lights. Its brightest companion sits 2.3′ away, which at 48× is cleanly split.
- 48×
- 1.08
- 1.25
- 13.0
- 2.3 · cleanly split
- APPARENT MAGNITUDE ()
- 5.77 · within reach
A is where the pair was the year it was measured — the ones above, in 2015, and a pair in a real orbit has moved since. The brightest companion is 7.6 magnitudes down on the star itself, which this far out from it is a faint speck beside a bright star rather than a matched pair.
APPARENT PLACE
] EQUINOX J2026.7Where a telescope has to be pointed today, which is not quite where the catalogue records the object: the coordinate grid itself has turned since the year 2000 the catalogue is referred to.
- RIGHT ASCENSION
- DECLINATION
- GRID TURNED SINCE
- 21.2
- PROPER MOTION SINCE
- 14.6
Computed for 2026-08-27 00:00 UT. Two things separate it from the catalogued position above: 12 Oph has moved under its own proper motion, and the coordinate grid has turned under it — about fifty arcseconds a year of precession since 2000, and the small nodding of the Earth’s axis on top of that. Aberration and refraction are not included, and neither is parallax; each is under an arcminute, which is also about as well as the catalogued position is known. The same figure for any date.
VARIABILITY
] BY DRACONIS SPOTTED ROTATING VARIABLE- RANGE, AS SAMPLED
- 5.76 – 5.78
No period is published for this star, so there is no cycle to count. The catalogue records that it varies and by how much, and not how often.
The range is the spread the Hipparcos satellite measured, converted to the visual scale. It is approximate: the satellite sampled the star on a schedule of its own, and where a star spends little of its cycle at an extreme — the floor of an eclipse, most obviously — the sampling can miss it altogether. The classification is the General Catalogue of Variable Stars’s. These elements as data.
DOUBLE STAR
] 1 PAIR| COMPONENTS | SEPARATION | POSITION ANGLE | MAGNITUDE | MEASURED |
|---|---|---|---|---|
| — | 139.1″ | 266° | 13.4 | 2015 |
Separation and position angle are as measured in the year given; a position angle is measured from north, through east. Washington Double Star Catalog 16364-0219.
CATALOG DATA
] 22 FIELDSThe raw catalogue values, as the source published them, with the error bars where one was published — sorted by what each set of figures is about rather than by the order they happened to be stored in.
WHAT IT IS MADE OF
What the object is in itself, rather than how it happens to look from here.
- Spectral type
- Surface temperature
- 5107
- Luminosity
- 0.40738
- Luminosity (bolometric)
- 0.4634
- Radius
- 0.872
- Mass
- 0.822
- Surface gravity (log g)
- Metallicity ([Fe/H])
- 0.04 ±0.037
- Age
- 1.21×10¹⁰
- Variability
- BY Draconis spotted rotating variable
- Variability type ()
- BY
HOW BRIGHT IT IS
What the light adds up to, measured through one filter at a time. A magnitude is a brightness on a backwards scale — the smaller the number, the brighter the object.
- Colour index (B−V)
- Variable magnitude, brightest
- Variable magnitude, faintest
WHERE IT IS AND HOW IT MOVES
Position, motion across the sky and the size it covers on it. These are measurements of the object as seen from here, so every one of them depends on where here is.
- Proper motion (RA)
- 455.22
- Proper motion (Dec)
- −307.63
- Radial velocity
- −12.1
OTHER NAMES AND NUMBERS
The identifiers other catalogues file this object under, for anyone joining this data to theirs.
- Variable-star designation
- V2133 Oph
- Washington Double Star id
- 16364-0219
WHERE THESE FIGURES CAME FROM
Which catalogue, paper or model each of the fields above was read from, where the source named one.
- Spectral type from
- SIMBAD (1999MSS...C05....0H, quality C)
- Stellar parameters from
- Gaia DR3 model fit (GSP-Phot, FLAME; RUWE ≤ 1.4)
- Metallicity from
- Median of 20 spectroscopic determinations in 24 papers, compiled from the literature (PASTEL, Soubiran+ 2016); the error bar is the scatter between them
ALSO KNOWN AS
] 6 DESIGNATIONS- Bayer/Flamsteed 12 Oph
- Gliese Gl 631
- HD HD 149661
- HIP HIP 81300
- HR HR 6171
- Variable star V2133 Oph
LOOK IT UP ELSEWHERE
] 3 SERVICESEach link carries the identifier printed beside it. Nothing on this page is a measurement of our own, so a number that disagrees with one of these is worth reporting — and a service that has never catalogued this object under this name will say so plainly.
- SIMBADHR 6171
Cross-identifications, measured values and the reference behind each of them.
- ADSobject:"HR 6171"
Papers indexed against this object rather than against the string, newest first.
- VizieR5″ around 249.0894 -2.3246
Every published table with a row at this position, searched by coordinates rather than by name.
CITE THIS PAGE
] DR1This page is live and its numbers move when an upstream refreshes, so the citation names the release the rows belong to rather than the day you read them. The release itself is frozen, republished as a bundle, and is what a data-availability statement should point at.
SpaceCatalog. 12 Oph [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/hd-149661
@misc{spacecatalog_hd-149661,
author = {{SpaceCatalog}},
title = {{12 Oph}},
howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
year = {2026},
url = {https://spacecatalog.org/object/hd-149661},
note = {Catalogue entry, data release DR1 (2026-08-21). Values from HYG Database v4.1.}
}The values above were taken from HYG Database v4.1 — CC-BY-SA-4.0. Citing this page does not replace citing that catalogue, and its licence is share-alike: the terms reach whatever you build from these rows.