This ATel will be of interest to those observers who have been follwing comet 108P during its current apparition. Denis Buczynski ------ Original Message ------ From: atel@astronomerstelegram.org To: buczynski8166@btinternet.com Sent: Tuesday, 25 Jan, 22 At 11:11 Subject: ATel #15177 ------------------------------------------------------------------------------<br> <br> The Astronomer's Telegram is free to read, free to publish, free to<br> use. Thanks to the support of our patrons, we can continue to<br> keep it free. <a target="_blank" href="https://www.patreon.com/astronomerstel">https://www.patreon.com/astronomerstel</a><br> ------------------------------------------------------------------------------<br> <br> The Astronomer's Telegram <a target="_blank" href="http://www.astronomerstelegram.org">http://www.astronomerstelegram.org</a><br> <br> ==============================================================================<br> ATEL #15177 ATEL #15177<br> <br> Title: Comet C/108P (Ciffreo) is not splitting<br> Author: Federico Manzini (SAS), Paolo Ochner (University of Padova;<br> INAF-OAPd), Virginio Oldani (SAS), Luigi R. Bedin (INAF-OAPd), Andrea<br> Reguitti (UNAB; INAF-OAPd), Jean Gabriel Bosch, Jean Fran��ois Soulier<br> Queries: <span class="wt_Email">manzini.ff@aruba.it</span><span></span><br> Posted: 25 Jan 2022; 11:10 UT<br> Subjects:Optical, Comet<br> <br> Comet C/108P was discovered by Jacqueline Ciffreo on November 8, 1985 with<br> the 0.9-m <br> Schmidt telescope of CERGA-France (IAUC 4135). Its short-term orbit was<br> calculated by D. Green <br> (IAUC 4137). <br> The comet was followed by our group in its current apparition since November<br> 7, 2021, when it <br> showed well-defined morphological structures in the inner coma. <br> Following some alerts of a possible fragmentation of the nucleus ( <a target="_blank" href="https://groups.io/g/comets-ml">https://groups.io/g/comets-ml</a><br> ), <br> an observation of the comet was scheduled on December 30, 2021 with the<br> INAF-OAPd 1.82-m Copernico telescope (Asiago Astrophysical Observatory,<br> Italy). <br> On the high-resolution CCD image, the false nucleus appeared very bright,<br> slightly elongated in PA <br> 30��, with an average FWHM of about 1.8 arcsec (about 1,300 km at the distance<br> of the comet). <br> The tail was oriented towards PA 245 deg. A bright condensation, elongated<br> in the E-W direction, was <br> visible in the coma at PA 90 deg, which appeared detached from the nuclear<br> region, with a center of <br> gravity about 7 arcsec east of the optocenter (about 5,250 km at the distance<br> of the comet) (Figure <br> 1). <br> A very similar morphological structure had already been observed during<br> the comet's last orbit in <br> December 2014, albeit with instruments of smaller diameter and lower resolution<br> (J.G. Bosch, A. <br> Maury, J.F. Soulier), in almost analogous geometric conditions to those<br> of 2021 (Figure 2). <br> Similar morphology was also observed about 1 month after the discovery<br> of the comet, by S. M. <br> Larson and D. Levy, who reported that CCD images obtained with 1.5-m and<br> 0.5-m telescopes in <br> December 1985 showed a detached dust tail extending over 20" to the north-east<br> of the nucleus <br> and curving in the direction of increasing position angle. The distance<br> of the point of maximum <br> intensity in the tail was about 6" from the nucleus (IAUC 4158, and Bull.<br> AAS 1986, Vol. 18, p.811). <br> In the same IAUC A.R. Klemola (Lick Observatory) wrote that an exposure<br> with the Crossley <br> reflector on 1985 Dec. 17.3 UT showed a sharp stellar object separated<br> by an almost clear gap <br> from a diffuse coma or tail feature. The center of the diffuse feature<br> was 5.6" to the northeast of the stellar object. <br> A more in-depth analysis, supported by a modelling of the inner coma that<br> takes into account the <br> dust outflow from discrete sources on the surface of the nucleus, shows<br> that this structure, <br> recurrently observed during previous apparitions of the comet, may originate<br> from a strong activity <br> of an area in near-polar position on a nucleus with a spin axis directed<br> approximately towards the <br> Sun (Figure 3). The dust outflow, emitted collimated in almost sunwards<br> direction, would be pushed <br> back by the radiation pressure and, due to the geometry of the observation,<br> would appear <br> projected onto the coma, thus creating a 'clump' effect that could resemble<br> a detached fragment <br> which, however, is not real. <br> <br> Figures are available at: <br> <a target="_blank" href="https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/ATel/C1985P/FiguresATEL108P.PDF">https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/ATel/C1985P/FiguresATEL108P.PDF</a><br> <br> Link: <a target="_blank" href="https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/ATel/C1985P/FiguresATEL108P.PDF">https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/ATel/C1985P/FiguresATEL108P.PDF</a><br> ------------------------------------------------------------------------------<br> Password Certification: Andrea Reguitti (<span class="wt_Email">andreareguitti@gmail.com</span><span></span>)<br> <a target="_blank" href="https://www.astronomerstelegram.org/?read=15177">https://www.astronomerstelegram.org/?read=15177</a><br> ==============================================================================<br> <br> <br> ==============================================================================<br> This is an automatically-generated notice. <br>
