Re: [comets-ml] Comet C/20ll L4 PanSTARRS Growing Anomalous Tail
- Hi Bob,
The anomalous tail is comprised of dust that has been ejected generally in
an anti-solar direction from the nucleus in past weeks and months, the
very heaviest particles traveling along essentially in the same track as the
nucleus itself, as if they were mini-PanSTARRS. In addition, progressively
lighter dust particles being pushed anti-solar more energetically are spread
out in a very thin sheet beyond the actual path followed by the nucleus,
rather like a broad continuous extension of the comet's fan tail.
When the comet's orbital plane is viewed face-on, the density of the
particles isn't great enough to reflect a lot of sunlight and so the region is
very faint and transparent. However, as the Earth comes ever closer to
passing through the comet's orbital plane we see this vast sheet of material
presented ever closer to edge-on.
When the orbital plane of a very dusty comet like PanSTARRS is viewed
edge-on, we are looking at this thin sheet of material which is only perhaps
5,000 - 10,000 miles thick, but millions of miles deep, projected upon
itself. This compounded total line-of-sight density of particles can then reflect
back toward Earth a great deal of sunlight and this "tail" becomes
Of course an anomalous tail does actually point physically toward the Sun
in space since it really is situated beyond the comet's orbital path. It is
just an illusion resulting from our viewing angle and perspective.
In a message dated 5/21/2013 12:38:56 P.M. Eastern Daylight Time,
Of course - that makes perfect sense! Thank you. My problem was I wasn't
thinking in 3 dimensions. So one last question. Is the long tail we
currently see debris in the comet's orbit toward the direction of the sun
or opposite the sun on the "farside" of the comet in the approximate
direction of its orbital motion?
Thank you again,
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