The description of the word you requested from the astronomical dictionary is given below.
continuum = [Latin] something without breaks
In general a continuum is a collection of all possibilities or values, without gaps.
In astronomy, the continuum is the name for the combination of all colors that an object such as the Sun emits, and also for the broad variation from color to color in how much light is emitted. Broad means: without looking at the little details, such as spectral lines. The continuum is determined mostly by the temperature of the object. The hotter the object is, the brighter it shines. The color at which an object shines brightest also depends on the temperature. Hot objects such as the Sun shine brightest in yellow light; less hot objects shine most in red light, and cool objects shine brightest in (invisible) infrared light.