![]() Image: Gerald Rhemann A true space oddity During January of this year, the IRTF analysis of 45P. As evident from these two comets, well-resolved inner comae are vital for detailed characterization of dust environments. In the narrow region of space where Helios detected the candidate dust particles, the spacecraft repeatedly traversed the trails of comets 45P/Honda-Mrkos-Pajduáková and 72P/Denning-Fujikawa with relatively high predicted dust uxes. Comet 45P captured on 22 December using a telescope from Farm Tivoli in Namibia, Africa. Although not bright enough to be seen with the naked eye it can be spotted with small/medium size telescopes. On New Years Day, the comet shone at apparent magnitude +7.1. ![]() These results suggest that comets 45P/HMP and 46P/Wirtanen have vastly different coma dust environments and that their dust expansion properties are distinct. Periodic comet 45P/Honda-Mrkos-Pajdusakova has now brightened sufficiently that it can be seen with small telescopes in the evening sky towards the west just after sunset. Additionally, we find that the radial profile of 46P/Wirtanen is azimuthally dependent on the sky-plane-projected solar position angle, while that of 45P/HMP is not. Comet 45/P HondaMrkosPajdukov, a tiny piece of ice and dust left over from the earliest days of the solar system, moves periodically around the Sun every 5.25 years. A little periodic comet is visiting the inner solar system over the next few months. Contrastingly, the radial profile slope of 46P/Wirtanen stays fairly constant over the observed time period at -1.05 ± 0.05. Comet 45P/Honda-Mrkos-Pajdusakova imaged by amateur astronomer Tim Puckett in 2011. The azimuthally averaged radial profile slope of comet 45P/HMP gradually changes from -1.81 ± 0.20 at 5.24 days preperihelion to -0.35 ± 0.16 at 74.41 days postperihelion. The radial profile slopes of these comets were measured in the R and HB-BC filters most representative of dust, and deviations from a radially expanding coma were identified as significant. From Redmond on the day of perihelion it will not be readily observable since it will be very close to the Sun, at a separation of only 9° from it. There was an unprecedented opportunity to study the inner dust coma environments, where the dust and gas are not entirely decoupled, of comets 45P/Honda-Mrkos-Pajdus̆áková (45P/HMP) from 2016 December 26 to 2017 March 15, and 46P/Wirtanen from 2018 November 10 to 2019 February 13, both in visible wavelengths. Comet 45P/Honda-Mrkos-Pajdusakova will make its closest approach to the Sun on 18 April, at a distance of 0.56 AU. ![]()
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