Cometary Science Newsletter

January 2023
Michael S. P. Kelley (

Refereed Articles

Abstracts of articles in press or recently published. Limited to 3000 characters.

Observations of a dust tail gap in comet C/2014 Q1 (PanSTARRS)

  • Afghan, Q 1,2
  • Jones, G.H. 1,2
  • Coates, A.J.1,2
  • Price, O.1,2
  1. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
  2. The Centre for Planetary Sciences at UCL/Birkbeck, London, UK

Cometary dust tails display a wide array of structures, most believed to be caused by a variable dust production, size distributions, fragmentation processes, and interactions with the solar wind, e.g. Price et al. (2019). However, not all these structures are fully understood. Here we report the discovery of a curious new dust tail feature, first noted in long period comet C/2014 Q1 (PanSTARRS) (Bolin et al., 2014), where a section of the dust tail was clearly missing. This implies that the comet underwent a dramatic temporary decrease in dust production near perihelion. The gap appeared on 2015 July 14, 8 days after perihelion at 0.318 au, and progressed along the tail, following the expected motion of the dust that should have been present. The gap corresponds to dust ejected between July 5 and July 12, and of beta > 0.01. Possible explanations for this gap are proposed.

Icarus (Published)

DOI: 10.1016/j.icarus.2022.115286

Microphysics of dust in a distant comet C/2017 K2 (PanSTARRS) retrieved by means of polarimetry

  • Kochergin, A. 1
  • Zubko, E. 2
  • Chornaya, E. 1
  • Zheltobryukhov, M. 1
  • Videen, G. 2,3
  • Kornienko, G. 1
  • Kim, S.S. 2,4
  1. Institute of Applied Astronomy of Russian Academy of Science, Russia
  2. Humanitas College, Kyung Hee University, South Korea
  3. Space Science Institute, USA
  4. Department of Astronomy and Space Science, Kyung Hee University, South Korea

We conducted the earliest polarimetric survey of Comet C/2017 K2 (PanSTARRS) over 10 epochs during February–March, 2021, while the comet’s heliocentric distance was decreasing from 7.135 au to 6.801 au. Within an aperture radius ρ = 10,000 km, we found slightly varying negative polarization with median value PQ ≈ –2.1% at phase angle α ≈ 8°. This appears in quantitative agreement with measurements of other distant comets. The negative polarization reveals submicron and micron-sized dust particles within the coma constrain the imaginary part of the refractive index in at least one type of particles to Im(m) ≤ 0.04. Models earlier developed in Kochergin et al. for the negative polarization in distant Comet 29P/Schwassmann–Wachmann are similar to the negative polarization of Comet C/2017 K2 (PanSTARRS), suggesting its coma could be populated by Mg-rich silicate particles and/or water-ice particles, which are mixed with organic particles and/or amorphous-carbon particles. Modeling dust motion suggests that the inner coma is populated by particles whose age is up to 15 days since their emanation from the nucleus.

Journal of Quantitative Spectroscopy and Radiative Transfer (In press)

DOI: 10.1016/j.jqsrt.2022.108471