[BAA Comets] [comets-ml] A new outburst of Comet 17P/Holmes

[Luca Buzzi]

Dear Richard,
thank you for this valuable study, well done.

Best regards,
Luca Buzzi
# 204



Il 19/05/2012 23:15, RICHARD MILES ha scritto:
> Comet 17P/Holmes is a fascinating comet having drawn our attention bigtime
> when it underwent a superoutburst brightening ~14 magnitudes on 2007 October
> 24. Interestingly, although its activity subsided, it did exhibit a clear
> outburst on 2009 Jan 04. The exact date is known thanks to monitoring by
> Luca Buzzi at Schiaparelli Obs. and by Richard Miles and George Faillace
> using the 2.0-m Faulkes Telescope North. The photometry can be seen here:
>
> http://www.britastro.org/~rmiles/Images/17P_2008-9_photometry.png
>
> In 2010 October, the comet reached aphelion at r = 5.188 AU and since then
> it has been approaching the Sun at an ever-increasing rate.
>
> The latest news is that although the cometary nucleus is still about 4.4 AU
> from the Sun, it has just undergone another distinct outburst, brightening
> by some 1.3 magnitudes as observed using the 2.0-m Faulkes Telescope South.
> Here is the photometry as measured using an aperture radius of 2.4":
>
> Date R mag
> Apr 13 21.1
> Apr 19 20.9
> May 15 19.7
> May 17 20.1
> May 18 20.2
>
> The outburst probably occurred on 2012 May 12+/-2 as deduced from images
> taken on each of the above 5 epochs. See:
>
> http://www.britastro.org/~rmiles/Images/17P_2012May_outburstA.png
>
> Comet Holmes has some unusual characteristics. It is likely to be a very
> slow rotator: one unofficial estimate is a rotation period of 44+/-2 days.
> Observers located in the southern hemisphere may find this object to be a
> rewarding target for study. Its current apparition comes to an end in about
> August but the next one (2013 March - 2013 September inclusive) will be
> favourable. Perihelion occurs near solar conjunction in 2014 March and it
> then moves northwards occupying a similar region of the sky to its famous
> 2007 apparition.
>
> Given that the 2007 superoutburst was much more energetic than its outburst
> on the occasion of its discovery in 1892, the physical integrity of the
> cometary nucleus may have been compromised in some way so we may have to
> expect the unexpected from this object during the next few years.
>
> Assistance from the Faulkes Telescope Project led by Dr Paul Roche is
> gratefully acknowledged (see for example:
> http://en.wikipedia.org/wiki/Faulkes_Telescope_Project ) and without which
> none of this work would have been possible.
>
> Richard Miles
> BAA
>
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