[BAA Comets] [comets-ml] 17P - current appearance

[Richard Miles]

Thanks Dave for the note re. Comet 17P/Holmes.

It is well worth keeping a close watch on this enigmatic object.

Back on April 12 it had a slight tail but this seems to have grown 
significantly since, which may be indicative of outburst activity.  On April 
12 it was mag 18.3, i.e. 1.3 mag brighter than the MPC (m1) value, and by 
May 31 it was 17.8 (0.8 mag brighter than the ephemeris).  Currently the MPC 
is indicating mag 18.4.

The evidence suggests that the object is subject to small outbursts at any 
point in its orbit.

After the 2012 May 12 outburst, 17P/Holmes declined in brightness reaching 
about mag 21.1 +/-0.3 by 2012 July when the MPC (m1) value corresponded to 
mag 20.9, i.e. in full agreement.  It is therefore significant that it was 
about 1.3 magnitudes brighter than predicted in April of this year.

Indeed looking at data prior to the superoutburst of 2007 October 23, I 
found some evidence that the comet may have undergone a mini-outburst a 
month or two prior to that time.

So the challenge for observers is to pick up such 'mini-outbursts' as it 
approaches perihelion (due on 2014 Mar 27). At present it is going through a 
very busy patch of sky crowded with stars so do make sure that the comet is 
not superimposed on a field star before announcing its next such outburst.

Good luck everyone,

Richard Miles
BAA


----- Original Message ----- 
From: "Dave Herald" <drherald at bigpond.net.au>
To: "Comets-ml" <Comets-ml at yahoogroups.com>
Sent: Saturday, June 15, 2013 3:44 PM
Subject: [comets-ml] 17P - current appearance


12 months ago there was a flurry of interest in an apparent small 
brightening of this comet. (message 19621 and subsequent).

The comet is currently located well south, at declination –49. The nuclear 
magnitude seems consistent with the MPC ephemeris – at around 17. However 
what may be of interest to some is that the comet is now exhibiting a short 
broad tail – about 15” long in PA 290.

Dave Herald
Murrumbateman, Australia

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