Eta Ophiuchi
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| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 10m 22.7s |
| Declination | -15° 43′ 29.7″ |
| Apparent magnitude (V) | 2.43 (3.0/3.5) |
| Characteristics | |
| Spectral type | A2.5 Va/A3 V |
| U-B color index | 0.09 |
| B-V color index | 0.05 |
| Variable type | ? |
| Astrometry | |
| Radial velocity (Rv) | -2.4 km/s |
| Proper motion (μ) | RA: 41.16 mas/yr Dec.: 97.65 mas/yr |
| Parallax (π) | 38.77 ± 0.86 mas |
| Distance | 84.1 ly (25.79 pc) |
| Absolute magnitude (MV) | 0.37 |
| Details | |
| Mass | 2.3/2.0 M☉ |
| Radius | 2.5/2.0 R☉ |
| Luminosity | 35/21 L☉ |
| Temperature | 8900/8600 K |
| Metallicity | ? |
| Rotation | 30 km/s. |
| Age | ? years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Ophiuchi (η Oph / η Ophiuchi) is a star in the constellation Ophiuchus. It also has the traditional name Sabik The Great.
η Oph is actually a binary star system that is difficult to resolve in amateur telescopes but whose true nature has been determined through use of more advanced techniques. The "primary" star (whose observational data make up the table in this article), which could nominally be referred to as η Oph A, is actually only slightly larger and warmer than its companion, η Oph B. Individually each star is a fairly unremarkable A class main sequence star, but as a binary pair they are unusual. Each star orbits around a common center in a very fast and highly elliptical orbit, making planetary formation impossible in this system and some stellar data imprecise.
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