Firmament

noun

1. (usually uncountable) The vault of the heavens, where the clouds, sun, moon, and stars can be seen; the heavens, the sky.
2. The field or sphere of an activity or interest.

   "the international fashion firmament"

3. In the geocentric Ptolemaic system, the eighth celestial sphere which carried the fixed stars; (by extension) any celestial sphere.
4. (obsolete except biblical) The abode of God and the angels; heaven.
5. A piece of jewellery worn in a headdress with numerous gems resembling stars in the sky.