Expansion rates of the comet 12P/Pons-Brooks, currently in outburst
ATel #16343; Jorma Ryske (Ursa Astronomical Association, Finland), Maria Gritsevich (University of Helsinki), Markku Nissinen (Ursa Astronomical Association), Ignacio Perez-Garcia (IAA-CSIC Granada, Spain) and Alberto J. Castro-Tirado (iAA-CSIC)
on 20 Nov 2023; 22:32 UT
Credential Certification: Alberto J. Castro-Tirado (ajct@iaa.es)
Over the past weeks we captured images of comet 12P/Pons-Brooks (see also ATEL #16194, 16202, 16229, 16254, 16270, 16316, 16338) using the 0.3m Viestikallio remote observatory in Finland and the new remote 0.3m Makroskooppi observatory in Spain. These observations facilitated the determination of physical parameters of the dust environment, including expansion rates.
Considering the outburst time reported in ATEL#16270 (Oct 5.16, 2023 UT), we determine the following dust halo expansion speeds: 330 m/s (Oct 9.74 UT), 250 m/s (Oct 12.76 UT), 220 m/s (Oct 17.74 UT) and 200 m/s (Oct 20.71 UT).
The comet 12P/Pons-Brooks is currently undergoing its fourth significant outburst in this orbit. This latest outburst began around Nov 14.5, 2023 UT. The comet is also closer to the sun, causing gases to ionize and fluoresce during the outburst. In the RGB color image, a faint but relatively long and wide blue tail is visible, indicating CO+ ions, along with a strong green halo around the comet's optical center, indicating C2 molecules.
In the black and white enlarged image of the nucleus, an interesting curved jet structure is discernible. An inverted narrowband UV image has been added (Semrock CN 3883Ã
filter passband 380nm - 395nm). In the CN band image, a large bright CN halo is visible. Also a distinct ion tail is visible, which is not CN molecules but some other ion.
Additional follow-up observations are being carried out at the BOOTES (Burst Observer and Optical Transient Exploring System) Global Network of Robotic Astronomical Observatories.
