Comets have two tails
Discussion
The APOD for today, 12/12/15, shows Comet Catalina, in the same frame as the Moon and Venus
http://apod.nasa.gov/apod/astropix.html
They all have them, but this pic shows especially well the two tails of the comet.
One is the ion tail, of charged particles caught up in the Solar Wind and pushed directly away from the Sun.
The other is the dust tail, of uncharged particles from the out-gassing comet core, that tracks behind the comet in its orbit, like the smoke from a falling firework.
My question is, why is there a dust tail? The comet and its effluent are all in free-fall around the Sun. Why is anything left behind along its track? We are used to anything mobile, like a steam train, leaving a trail of smoke in the stiller atmosphere, or stationary chimneys having their smoke blown away in a trail as the atmosphere moves. But there ain't no atmosphere! And anything parting from the comet that isn't blown away by the Solar Wind is still in free-fall and should form a dense cloud around the comet.
So why is it left behind, like a smoke trail?
John
http://apod.nasa.gov/apod/astropix.html
They all have them, but this pic shows especially well the two tails of the comet.
One is the ion tail, of charged particles caught up in the Solar Wind and pushed directly away from the Sun.
The other is the dust tail, of uncharged particles from the out-gassing comet core, that tracks behind the comet in its orbit, like the smoke from a falling firework.
My question is, why is there a dust tail? The comet and its effluent are all in free-fall around the Sun. Why is anything left behind along its track? We are used to anything mobile, like a steam train, leaving a trail of smoke in the stiller atmosphere, or stationary chimneys having their smoke blown away in a trail as the atmosphere moves. But there ain't no atmosphere! And anything parting from the comet that isn't blown away by the Solar Wind is still in free-fall and should form a dense cloud around the comet.
So why is it left behind, like a smoke trail?
John
The velocity of the individual particles is changed due to the "drag" exerted on them by sunlight and/or the solar wind - so they assume their own individual orbits separate to the nucleus of the comet itself. Over time the orbits of the particles deviate making them assume a "tail".
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