Thermal radiation explorer

A Dyson sphere doesn't hide the star.
It just reddens it.

Wrap the Sun in a shell and its entire light output is intercepted, used, and re-radiated as waste heat. Drag the shell inward or outward: the total energy never changes — only the wavelength it comes out at. And because the shell can never be hotter than the Sun's surface, it can only ever cool.

Reading the chart. Gold is the bare Sun (5772 K). The moving curve is the shell, tinted with its own true blackbody color. Both curves are normalized to the same area — that's energy conservation: the shell radiates every watt the Sun emits, just spread across a colossal, cooler surface and shifted toward the infrared. Slide it in far enough and the peak climbs back into visible light; the shell would begin to glow a dull red, then orange, like a heated stove element the size of a planet's orbit.