19P/Borrelly analysis
Comparison and analysis of several amateur images
Thanks to
Dr. Nalin Samarasinha of
the PSI
Planetary Science Institute,
a professional astronomer exploring the comet
since years, more light
is finally coming into the dark.
It is very interesting, that the long tail on our images is a sunward
tail and not the intrinsic tail (I was really shocked when I heard about this).
This means, that the observation normally can't be a fragment, because non-gravitational forces can push fragments only in
the direction of intrinsic tails effected
by solar winds.
To check out the origin of tails it is very recommended
to load the ephemeris table of the
JPL (Jet Propulsion
Laboratory) on their
HORIZONS
Web-Interface.
With the OBSERVER Ephemeris Type and the Table setting
feature
"Sub Sun Pos, Ang & Dis" you find the position angle of the comet orientated to
the Sun.
So it is easy to find out, that 19P/Borrelly's long tail is a sunward
tail. Here are the ephemeris.
Based on these knowledge, we can suppose, that the feature we observed the last months is a dust feature.
This assumption
can also be substantiated, if we go back to the DS1 Mission of the NASA
in September 2001.
On the images of the integrated camera on board of the Space probe two active polar
jets are visible in rough direction to the Sun.
Follow this
link
please and download the PDF text for free to see the images. (Sign in is
nescessary).
The new phenomenon could be a dust feature corresponding to the same polar sunward orientated jets they observed on the DS1 mission.
To verify
this assumption Dr. Nalin Samarashina checked the geometry of our observation
and find out, that the pole which was the origin location for the jets in 2001
is now in total darkness.
In May 2009 the observed jets are coming from a location on the
opposite pole of the comet. The Sun is actually only about 30� from this
opposing pole. Somebody would see the Sun in about 60� altitude from there.
We can assume now, that the comet is currently sending jets from the opposing pole in roughly direction to the Sun.
19P/Borrelly between March, 20 and June, 12 2009 All stars are removed.
After Dr. Nalin Samarasinha's indications I produced a gif animation of comet Borrelly with images taken between March,20 and June,12 2009.
Totally 11 images are processed
with exp.times between 65min and 240min. taken with 12" SCT f-6.532 and CCD
ST10XME.
The dates of the exposures: 03-20; 03-25; 04-01; 04-12; 04-16; 05-07; 05-18;
05-21; 05-22; 05-24; 06-12.
At the beginning of the sequence
you see also a small tail in PA 216�.
The conspicuous small tail (~11") with one (or more) knots in general direction
to the sunward tail is lying between PA 307� (03-20) and PA 311� (06-12).
The long sunward tail (~10') is lying between PA 293� (03-20) and PA 302�
(06-12).
The intrinsic tail (1') is lying between PA 125� (03-20) and PA 123� (06-12).
Here is the same animation without stops and another one with stars.
19P/Borrelly between March, 20 and June, 12 2009