Observation of a dust spiral structure in periodic comet P/2010 H2 (Vales)

We observed the comet P/2010 H2 (Vales) in moonless conditions on May 1, 2010 using B, V and R photometric filters, as well as with the clear filter on the 0.6 m, f/3.3 Cichocki telescope at the Crni Vrh Observatory. The exposures, all of 8 minutes duration, were tracked on the comet and obtained between 19:46 and 20:31 UT. The pixel scale was 0.93 arcseconds.

Unfiltered and unprocessed image, obtained on 2010 May 1.8489UT (start of 8-minute exposure). Copyright © 2010 by J. Skvarč, Črni Vrh Observatory.

All images exhibit slightly asymmetrical coma. On the highest SNR image, taken with the clear filter, the coma has a 1.9 x 2.0 arcminute axis length. The axis of symmetry is at PA = 134 +- 5 degrees, measured from the central condensation towards the middle of the wider part of the coma. No obvious tail or any other structure is been seen on any od the unprocessed images, regardless of contrast stretching or false colouring of the images.

To resolve details inside the coma the images were processed with the wavelet decomposition tool of the IRIS software. Rather remarkable details become visible. There is a blob of ejected material at 14 +- 1 arcseconds (projected distance from the comet 22000 km) at PA of 215 +- 3 degrees. Images taken with V, R and clear filters show a distinct spiral structure emanating from the comet at a single spot located at the PA = 240 +- 5 degrees. Nothing like this is seen on the B filter image. Especially the clear filter image is very suggestive of the explanation that we are looking at the dust ejection process. The stream of material is emanating from the comet nucleus and is aligned along the line of sight with a spiral of 1 arc-minute (93000 km at the comet distance) diameter.

Rotational gradient filtering with angles of 30 or 45 degrees reveals basically the same features but with lower contrast. False-color images, on which this analysis has been made, are added below.

W unfiltered image, obtained on 2010 May 1.8489UT (start of 8-minute exposure). Copyright © 2010 by J. Skvarč, Črni Vrh Observatory.