# air mass

> optical path length through Earth’s atmosphere for light from a celestial source

**Wikidata**: [Q352923](https://www.wikidata.org/wiki/Q352923)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Air_mass_(astronomy))  
**Source**: https://4ort.xyz/entity/air-mass-q352923


## References

1. Freebase Data Dumps. 2013