the beauty of a comet

"Pete Lawrence" wrote in message
...
On Fri, 7 Jan 2005 09:44:21 -0000, "Robert Geake"
wrote:

"manastro" wrote in message
. ..
A picture of this beautiful comet.
http://www.astronomike.net/fr_image_12384.html

Other picture and an animation when I can connect to my site :-(
http://perso.wanadoo.fr/passion.azur/

I had a discussion with the bird and we could not decide
about the tails of a comet. We know one is the particle
trail left by the comet and the other is the solar wind(we
think) but in manasto's piccy wich is which AND how do
we define which is which with other comets???

As a comet's nucleus approaches the Sun, it heats and starts to become
active. Material is geysered out into space. A the nucleus rotates,
this material gets wrapped around the nucleus (it's often possible to
image these jets at work - they have a spiral appearence). This
material goes to form the coma of the comet (the comet's head).

Some of this material is ejected from the nucleus so violently that it
leaves the head altogether. Heavier particles of dust spread along
the orbit of the comet. As there will be a range of directions of
ejection and a range of particulate masses, the dust tends to fan into
a wide so called 'dust tail'. Typically this forms a wide sweeping
arc away from the comet's head. It typically also appears rather
yellow in colour.

The solar wind also interracts with the head of the comet. Gas
released from the nucleus becomes charged and is carried, by the solar
wind, in a direction opposite to the Sun. This gas plasma stream is
called the gas or ion tail. It is typically very thin and typically
blue in colour.

In manasto's beautiful photo, the gas (ion) tail is the long one
pointing away from the head of the comet to the left, while the short
stubby one pointing to the right is the dust tail. They look a bit
odd with Machholz simply due to the line of sight that we have. We're
looking down into the dust tail which makes it look short and stubby.
However, we're looking along the ion tail so it's shown in all it's
glory.

--
Pete
http://www.digitalsky.org.uk
Global Projects - http://www.globalobservers.net

Cheers Pete

Elequently explained!

Rob