A substance which radiates light when heated to a high temperature is said to be

A substance that radiates light when heated to a high temperature is said to be incandescent. This process, known as incandescence, involves the emission of thermal radiation from a hot object [t1][t3]. Unlike luminescence, which is light emission not resulting from heat (often called 'cold light'), incandescence occurs when the atoms of a material are in a high state of thermal agitation [t4][t8]. Common examples include the tungsten filament in traditional light bulbs, which glows as it reaches high temperatures due to electric current, and glowing coal [t1][t3][t6]. While all matter above absolute zero emits thermal radiation, it only becomes visible as light when the temperature is sufficiently high, typically above 800 K [t3][t9]. In contrast, fluorescence and phosphorescence are types of photoluminescence where light is emitted following the absorption of photons, rather than through thermal heating [t5][t8].

Sources

1. [1] https://www.britannica.com/science/luminescence