Re: SOHO comets in 2008
- --- In firstname.lastname@example.org, Seiichi Yoshida <comet@...> wrote:
> Dear colleagues,
> Three SOHO comets (three groups of SOHO comets) are expected to
> in 2008.Hi all,
>  C/2003 T12 ( SOHO )
> It was pointed out to be possibly short periodic in
> M.P.E.C. 2004-K33.
> Hirohisa Sato calculated the short periodic orbit with a period of
> 4.3 years. I calculated the next return of this comet including
> perturbations based on Sato's orbit. The next perihelion date will
> be around 2008 Feb. 23.
> The condition in this return is very good, and the comet will be
> bright and observable on the ground.
> But the comet is not observable at all before the perihelion
> passage. It must be too faint to catch in the SOHO/LASCO images.
> Therefore, a bright comet will suddenly appear in the evening sky
> after the perihelion passage.
C/2003 T12 was observed for only 2 days in SOHO LASCO C3 with a pixel
size of about 50 arcseconds. Whatever orbital elements are computed
from these observations, the result will be only a rough approximation
of the true orbit.
I have used all C3 observations with the same weight to compute
elements with EXORB, integrated them with SOLEX and found a perihelion
date of 2008 February 12 not far from 2008 Feb. 23.
To estimate the uncertainty of the perihelion time I did 50 Monte
runs with EXORB and found a semimajor axis of
a = 2.57 +/- 0.36 a.u. (mean dev.) or P = 4.16 +/- 0.865 years.
A second try with 50 Monte Carlo runs gave
a = 2.53 +/- 0.35 a.u. (mean dev) or P = 4.065 +/- 0.835 years.
While these computations confirm that this is probably a short period
comet, they show also that the orbital period is not well determined.
The mean deviation of the orbital periods is 0.85 years or about
ten months, so we don't know at which time of the year the comet
will return (or even has returned unnoticed).