Firmament

Firmament, a noun (origin 1250-1300 Middle English) refers to the arch of the sky or heavens.  It also refers to a field or sphere of interest or activity.   In the bible, in the book of Genesis it says that God created a space or firmament to separate the waters from above from the waters below and called the space heaven.  

A few examples for use in a sentence:

“The stars shine brightly across the firmament"  

“Oprah is more than an institution.  She is a bright star in the firmament.  I can’t imagine a greater success than she has enjoyed”  Phil Donahue

The spacious firmament on high, 
With all the blue ethereal sky, 
An spangled heavens, a shining frame 
Their great Original proclaim. 
Th’unwearied sun from day to day
Does his Creator’s power display;
And publishes to every land
The work of an Almighty hand 

Joseph Addison - In The Spectator