tail of a comet

[fatgaz]

in the same quiz as the sunlight one was this question "when a comit is traveling away from the sun where is the comets tail ahead or behind" i answered behind correct answer was ahead my question is how can the comet PUSH it`s own tail as the tail is not solid so it would pass right through it

[gen2]

The comet does not push, pull or exert any other force on its tail. It is the solar wind thats pushes the fine particles out from the comet and away from the sun. The tail of a comet therefore always goes outwards from the sun - behind it as it approaches and in front of it as it departs.

[dundurn]

The problem is in thinking of the comet's tail as being 'behind' or 'in front of' the comet; it is neither. The comet is in orbit round the Sun. As its orbit brings it closer to the Sun it starts to melt giving off gas and dust particles. These are small enough to be affected by the solar wind and start to move further away from the Sun. In doing so they are illuminated by the Sun and we see them as a 'tail' to the comet. In some cases the gas and dust show up as two separate tails; the gas being more affected than the (larger) dust particles. For an Earth-based observer the tail appears to be lagging behind the comet. After the comet has rounded the Sun the same optical illusion works in reverse and now the tail appears to be in front of the comet.