is it also due to solar wind? if so why is it in a different direction than the gaz tail?
The coma around the comet emits a large tail when solar wind and radiation pressure reach the comet; the tail is made up of dust and gas escaping the Nucleus of the comet.
The tail it self does not emit light but it reflects the light of the sun and start glowing because they are become ionized by the UV radiation.
The dust tail is physical debris that it ablated from the comet by solar radiation, and it tends to trail the direction of travel of the comet. The ion (gas) tail often points in a different direction because the gases are less massive than the dust/ice, etc and are carried away from the direction of the Sun by the solar wind. There are times when the dust and gas tails coincide, and there are times when they can appear to point in opposite directions from our vantage point. We seen the comets' tails as if they were projected on a 2-D sky, but keep in mind that apart from that X-Y alignment, there are also Z-components (toward or away from us) that we cannot observe.
Some people don't realize that the tail always points away from the Sun, regardelss of which way the comet is moving. Which means that, when the comet has rounded the sun and is on its way out of the system again, its tail is not a tail at all, it's a ... nose?
:P Indeed it is a nose. The ion tail always points directly outwards from the sun, no matter which way the comet is heading (aka towards the sun or away from the sun). While the dust tail (being heavier particulate material) tends to slope downwards and fall towards any local gravitational areas.
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