fir·ma·ment 
/ˈfɚməmənt/ noun
/ˈfɚməmənt/ noun [noncount] formal + literary : the sky
▪ meteors flashing across the firmament — sometimes used figuratively to refer to an area of interest or activity ▪ He was once the brightest star in the literary firmament.
▪ meteors flashing across the firmament — sometimes used figuratively to refer to an area of interest or activity ▪ He was once the brightest star in the literary firmament.
