Brown dwarfs of spectral type T have surface temperatures below 1300 K. We are also familiar with a group of objects that emit infrared radiation at even lower temperatures, typically a few hundred kelvins. These objects are called:

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These objects are known as planets, specifically "cold planets" or "ice giants" such as Neptune and Uranus in our own solar system. They emit infrared radiation due to their internal heat and are not capable of undergoing nuclear fusion like stars or brown dwarfs.

Brown Dwarfs of Spectral Type T Have Surface Temperatures Below