posted by dia .
why we don't see comets until they are mear the sun?
Because (1) the sun, when close, comet by reflection. (2) The sun also evaporates the icy head of the comma faster when it is closer to the sun, to provide more material to reflect light.
(3) A comet tends to be closer to the Earth when it is near the sun, compared to when it is beyond the orbit of Jupiter. This makes it appear brighter and larger.