# Messier 40

> Optical double star in the constellation Ursa Major.

**Wikidata**: [Q13886](https://www.wikidata.org/wiki/Q13886)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Winnecke_4)  
**Source**: https://4ort.xyz/entity/messier-40


## References

1. [Messier 40](http://www.messier.seds.org/m/m040.html)
2. SIMBAD
3. Washington Double Star Catalog
4. [Charles Messier's Catalog of Nebulae and Star Clusters](http://www.messier.seds.org/xtra/history/m-cat.html)
5. Freebase Data Dumps. 2013
6. The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog