Question

why does comet show long tail when it reach near the sun

Answer 1

Heya,

Sunlight and solar wind sweep the dust and gas of the coma into trailing tails.

Because sunlight and solar wind always flow outward from our Sun's surface, the tails always point away from our Sun no matter what direction the comet is moving in its orbit.

HOPE IT HELPS:-))

Answer 2

As a comet approaches the Sun, it starts to heat up. The ice transforms directly from a solid to a vapor, releasing the dust particles embedded inside. Sunlight and the stream of charged particles flowing from the Sun – the solar wind – sweeps the evaporated material and dust back in a long tail.