p17 Holmes

A Calamari in the sky with diamonds

On October 24, 2007 the comet Holmes p17 experienced a sudden outburst. In a few hours its luminosity increased from magnitude 17 to about 2.5, of xx folds becoming an easy naked eye target. On the following day the chioma showed an enormous expanding shell that developed a tail that lasted several days. This picture summarized my imaging effort of this amazing solar system interloper. All pictures were shot through the Megrez 80 Apo at a focal length of 384 mm. North is up.

The everchanging shape of Holmes chioma and tail from November 5 until the 10th 2007 (north is up).

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November 6th (0:20 UT)

The inner chioma does not seem to show many features. However if the image is treated with a radial gradient filter (Larson-Sekanina filter) several features can be recognized, including small jet-like fountains erupting from the false nucleus. The field is 41' wide.

November 6th (0:20 UT)

The inner chioma is shown here in an hybrid picture rendering both the its naturalistic aspect and also the vision of the innner jets enhanced by a radial filter. At this time the inner chioma was about 18' in diameter.

November 6th (0:20 UT)

The tail begun developing at the beginning of November and declined soon after reaching a peak of development around November 3. This shot shows the ion tail and the immense ionised head. The inner chioma is much brighter and it has been overlaid over the deep shot. Canon 350D, Megrez 80, f 4.8, 20x4', iso 800. Published on the December 2007 issue of Coelum.

November 6th (0:20 UT)

The day after the chioma was slightly larger. This elaboration presents together the linear stretching oversimposed with a an image processed through wavelet filters, to bring out some details of the inner tail. The field is 41' wide.

November 6th (0:20 UT)

The data has been processed with a L-S filter to show the jets emerging from the false nucleus.

November 7th (0:20 UT)

The day after the chioma was slightly larger, but the tail was weaker and it begun showing the disconnection.

November 18

Here Holmes is passing through the a Persei moving cluster, a physical association of young stars surrounding Mirfak deeply immersed in the comet outskirt. The beautifully blue stars of the association surround the comet, now reduced to an immense chioma showing no sign of ionisation. The field has been aligned on the stars, so the false nucleus can be seen leaving a thin trail revealing its proper motion. By this time the chioma is huge, being approximately 38' by 51': this covers twice the area of the full moon!

30x8' at iso 800.

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Send anything that comes to mind to Gimmi Ratto gimmi@in.pi.cnr.it