Abstract

22P/Kopff images were taken with Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) 3ch simultaneous CCD cameras on the Ishigakijima astronomical observatory 105-cm telescope and a 2kCCD camera on the Kiso 105-cm Schmidt telescope from 2009 August to December after the passage of its perihelion on 2009 May 25. We confirmed that the near-nuclear fan-shaped jet structure extended toward the south. Whereas we detected a dust trail structure on the project orbit of the parent nucleus, we could not confirm the obvious neck-line structure. We deduced a pole orientation of (⁠|$ \alpha_{\rm pl}$| , |$ \delta_{\rm pl}$| ) |$ =$| (302|$ \pm$| 30, 62|$ \pm$| 10) or (⁠|$ \alpha_{\rm pl}$| , |$ \delta_{\rm pl}$| ) |$ =$| (122|$ \pm$| 30, |$-$| 62 |$ \pm$| 10) in the case of prograde or retrograde rotation, based on the fan-shaped jet. In addition, we conducted a model simulation of the dust orbital evolution, and found that the observed dust morphology of the fan-shaped jet and dust trail can well explain the dust emission near the south polar region. Finally, we conclude that the surface of 22P/Kopff is becoming largely dormant, but the polar region is still active, as we saw in the Deep Space 1 image of 19P/Borrelly.

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