# 21 Ophiuchi

> star in the constellation Ophiuchus

**Wikidata**: [Q115610](https://www.wikidata.org/wiki/Q115610)  
**Source**: https://4ort.xyz/entity/21-ophiuchi


## References

1. SIMBAD
2. Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5
3. Gaia Data Release 2
4. VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
5. The Tycho double star catalogue
6. Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system
7. Fundamental Parameters of CP Stars observed at the 6-m Telescope. I. Observations in 2009-2011
8. Validation of the new Hipparcos reduction