Despite appearing stubbornly dark to optical telescopes, what radiation do dust grains in dark nebulae often emit?

Answer

Infrared radiation

The dust grains within the nebula become warmed by surrounding starlight, causing them to glow faintly by emitting radiation in the infrared region of the spectrum.

Despite appearing stubbornly dark to optical telescopes, what radiation do dust grains in dark nebulae often emit?

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