Cometary activity found on asteroidal object 2004 TU12

(J. Lacruz, La Cañada Observatory J87)

The NEO 2004 TU12 was discovered on 2004 Oct. the 10th by the Siding Spring Survey (Australia) and announced on MPEC 2004-T55, it was classified as an amor object. The night of 2004 Nov the 12th I was at La Cañada, planning observation while waiting for interesting objects to raise, I saw this bright NEO about the meridian in the planetary program, to check that all the systems where working I started a series of images. In the very first images of 30 seconds I noticed a faint trace to the north-est originating at the neo and thought it could be a comet. Stacking many images the trace was visible as a straight tail moving as a whole with the nucleus.

La Cañada discovery image, it was 2.5 days past perihelion and crossing the ecliptic (nodes)

2004 TU12 sporting a straight collimated thin tail

The CBAT (central bureau for astronomical telegrams) published the IAUC 8436 on 2004 Nov 12th, with the report of the tail detection, a=3 e=0.6 i = 27.8, q= 1.22 Tisserand(j)=2.85 , the new object designation is P/2004 TU12, on 2004 Nov the 24th it was numbered as 162P IAUC 8445.

Circular No. 8436 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION COMET P/2004 TU_12 (SIDING SPRING) An apparently asteroidal object discovered on Oct. 10 by the Siding Spring Survey (announced as 2004 TU_12 on MPEC 2004-T55; discovery observation below) has been found to show a short eastward tail. CCD images taken over 2.5 hr with the 0.36-m "SoTIE" reflector at Las Campanas by F. Mallia, G. Masi, and R. Wilcox on Nov. 12.0 UT show a tail about 2' long in p.a. 70 deg (the "head" appearing like stars in the field (FWHM about 3"). Eighty 30-s CCD images taken on Nov. 12.8 by J. Lacruz (La Canada, Spain) show a sharp tail 4' long in p.a. 69 deg (and total mag 14.3).

Note the fact that the observations on Nov.12.o UT reported in the IAUC, sent by Masi et al. where published still under asteroidal designation in the 2004 Nov. the 12th Daliy Orbit Update :

K04T12U 2C2004 11 12.04523 22 51 33.56 -10 00 17.0 14.2 R EV056I05
K04T12U 2C2004 11 12.04620 22 51 33.58 -10 00 12.1 14.1 R EV056I05
K04T12U 2C2004 11 12.05008 22 51 33.78 -09 59 53.5 14.1 R EV056I05
K04T12U 2C2004 11 12.05494 22 51 34.02 -09 59 29.8 14.1 R EV056I05

However, the observations by J. Lacruz on Nov. 12.8 reported in the same IAUC circular, where published under the new cometary designation some three days later in MPEC 2004-V75 : COMET P/2004 TU12 (SIDING SPRING)

PK04T12U C2004 11 12.76709 22 52 14.38 -09 02 23.2 14.3 T EV075J87
PK04T12U C2004 11 12.76947 22 52 14.49 -09 02 12.1 14.3 T EV075J87
PK04T12U C2004 11 12.77228 22 52 14.64 -09 01 58.5 14.3 T EV075J87

Period of rotation

A light curve was obtained combining several photometric observations from stations J87 La Cañada, 213 Montcabre and Guadarrama.

Light curve of 162P phased to a period of 33 hours

The data seems to fit reasonably well to a period of about 33hr.

Recurrent activity

On 2004 Nov the 14th, three days after the initial detection, Jose Manteca posts to comets-ml images of the comet from Begues Observatory, Reiner Stoss notices a disconnection event on this images, Ramón Naves posts to observadores_cometas list images of the disconnection.

On 2004 Nov The 19th no tail was visible
No tail was visible

On 2004 Dec the 12th the tail is back on
The tail turns on again

Analysis of the tail

Seiichi Yoshida analyzed the comet's tail, discarding the tail generated by an impact scenario, Seiichi noticed that the directions of the dust and the ionic tails as seen from the Earth on 2004 Nov the 12th were respectively 30 and 69 degrees, so he made clear that the tail should be an ion tail. On the other hand, a dust tail would have had a spread aspect. In my view, the recurring activity shown, also points to an ice sublimation driven ionic tail and not to a dust tail.


Comet 162P/Siding Spring: A Surprisingly Large Nucleus


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