Comets appear dim as they move away from the Sun because the evaporating material decreases, making the tail less visible.
NCERT Book Curiosity Science Class 6
Class 6 Science NCERT Chapter 12
Why do comets appear dim when they move away from the Sun?
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Comets appear dim when they move away from the Sun because the solar heat that causes their icy core to vaporize decreases. As a result, the coma and tail shrink, reducing their brightness as they recede into colder, darker space.
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