Cometary Science Newsletter

Issue
87
Month
June 2022
Editor
Michael S. P. Kelley (msk@astro.umd.edu)

Refereed Articles

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

Optical observations and dust modelling of comet 156P/Russell-LINEAR

  • K.Aravind 1,2
  • Prithish Halder 1,3
  • Shashikiran Ganesh 1
  • Devendra Sahu 3
  • Miquel Serra-Ricart 4,5
  • José J. Chambó 6
  • Dorje Angchuk 3
  • Thirupathi Sivarani 3
  1. Physical Research Laboratory, Navarangpura, Ahmedabad, 380058, Gujarat, India
  2. Institute of Technology Gandhinagar, Palaj, Gandhinagar, 382355, Gujarat, India
  3. Indian Institute of Astrophysics, Koramangala, Bangalore, 560034, Karnataka, India
  4. Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, La Laguna, E-38205, Canarias, Spain
  5. Departamento de Astrofísica, Universidad de La Laguna, La Laguna, E-38205, Canarias, Spain
  6. Cometografia.es, Vallés, E-46818, Valencia, Spain

Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from CN (∆ν = 0), C3(λ4050 ̊A), C2(∆ν = +1) and C2(∆ν = 0) can be observed during both the epochs of our observations. The Q(C2)/Q(CN) ratio classifies the comet as a typical comet. The imaging data reveals the presence of jets. The dust emission from the comet is observed to have a non-steady state outflow due to the presence of these strong jets which subside in later epochs, resulting in a steady state outflow. Polarimetric study at two different phase angles reveals the degree of polarization to be comparable to Jupiter family comets at similar phase angles. Localized variations in polarization values are observed in the coma. The dust modelling studies suggest the presence of high amount of silicate/low absorbing material and indicate the coma to be dominated by higher amount of large size grains with low porosity having power law size distribution index = 2.4. The observed activity and dust properties points to a similarity to another Jupiter family comet, 67P/Churyumov–Gerasimenko.

Icarus (Published)

DOI: 10.1016/j.icarus.2022.115042 arXiv: 2204.09727

The Lingering Death of Periodic Near-Sun Comet 323P/SOHO

  • Man-To Hui 1
  • David J. Tholen 2
  • Rainer Kracht 3
  • Chan-Kao Chang 4
  • Paul A. Wiegert 5,6
  • Quan-Zhi Ye 7
  • Max Mutchler 8
  1. State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology, Macau
  2. Institute for Astronomy, University of Hawai‘i, USA
  3. Elmshorn, Schleswig-Holstein, Germany
  4. Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
  5. Department of Physics and Astronomy, The University of Western Ontario, Canada
  6. Institute for Earth and Space Exploration, The University of Western Ontario, Canada
  7. Department of Astronomy, University of Maryland, College Park, USA
  8. Space Telescope Science Institute, USA

We observed near-Sun comet 323P/SOHO for the first time using ground and space telescopes. In late December 2020, the object was recovered at Subaru showing no cometary features on its way to perihelion. However, in our postperihelion observations it developed a long narrow tail mimicking a disintegrated comet. The ejecta, comprised of at least mm-sized dust with power-law size distribution index 3.2±0.2, was impulsively produced shortly after the perihelion passage, during which ≳0.1-10% of the nucleus mass was shed due to excessive thermal stress and rotational disruption. Two fragments of ∼20 m in radius (assuming a geometric albedo of 0.15) were seen in HST observations from early March 2021. The nucleus, with an effective radius of 86±3 m (the same albedo assumed) and an aspect ratio of ~0.7, has a rotation period of 0.522 hr, which is the shortest for known comets in the solar system and implies cohesive strength ≳10-100 Pa in the interior. The colour of the object was freakish, and how it changed temporally has never been previously observed. Using our astrometry, we found a strong nongravitational effect following a heliocentric dependency of rH−8.5 in the transverse motion of the object. Our N-body integration reveals that 323P has a likelihood of 99.7% to collide with the Sun in the next two millennia driven by the ν6 secular resonance.

The Astronomical Journal (In press)

NASA ADS: 2022arXiv220302999H arXiv: 2203.02999

Hubble Space Telescope Detection of the Nucleus of Comet C/2014 UN271 (Bernardinelli–Bernstein)

  • Man-To Hui 1
  • David Jewitt 2,3
  • Liang-Liang Yu 1
  • Max Mutchler 4
  1. State Key Laboratory of Lunar and Planetary Science, Macau University of Science and Technology, Macau
  2. Department of Earth, Planetary and Space Sciences, UCLA, USA
  3. Department of Physics and Astronomy, UCLA, USA
  4. Space Telescope Science Institute, Baltimore, USA

We present a high-resolution observation of the distant comet C/2014 UN271 (Bernardinelli-Bernstein) using the Hubble Space Telescope on 2022 January 8. The signal of the nucleus was successfully isolated by means of a nucleus extraction technique, with an apparent V-band magnitude measured to be 21.65 ± 0.11, corresponding to an absolute magnitude of 8.63 ± 0.11. The product of the visual geometric albedo with the effective radius squared is pVRn2 = 157 ± 16 km2. If the ALMA observation by Lellouch et al. refers to a bare nucleus, we derived a visual geometric albedo of 0.033 ± 0.009. If dust contamination of the ALMA signal is present at the maximum allowed level (24%), we found an albedo of 0.044 ± 0.012 for the nucleus having an effective diameter of 119 ± 15 km. In either case, we confirm that C/2014 UN271 is the largest long-period comet ever detected. Judging from the measured surface brightness profile of the coma, whose logarithmic gradient varies azimuthally between ~1.0 and 1.7 as a consequence of solar radiation pressure, the mass production is consistent with steady-state production but not with impulsive ejection, as would be produced by an outburst. Using aperture photometry, we estimated an enormous (albeit uncertain) mass-loss rate of ~103 kg s-1 at a heliocentric distance of ~20 au.

The Astrophyiscal Journal Letters (Published)

DOI: 10.3847/2041-8213/ac626a NASA ADS: 2022ApJ...929L..12H arXiv: 2202.13168

On the dust production of active asteroid (3200) Phaethon in 2009: What the DESTINY+ spaceprobe could encounter

  • Zubko, E. 1,2
  • Kochergin, A. 3
  • Videen, G. 1,4,5
  • Chornaya, E. 3
  • Nozdrachev, T. 6
  • Zheltobryukhov, M. 3
  • Kim, S.S. 1
  • Wada, K. 2
  1. Kyung Hee University, South Korea.
  2. Planetary Exploration Research Center, Chiba Institute of Technology, Japan.
  3. Institute of Applied Astronomy of RAS, Russia.
  4. Space Science Institute, USA.
  5. Texas A&M University, USA.
  6. Far Eastern Federal University, Russia.

Asteroid (3200) Phaethon is long known to be a parent body of the Geminid meteoroid stream. While replenishment of the Geminid suggests regular emanation of dust from Phaethon, its comet-like activity was first detected only in June of 2009 (Jewitt & Li 2010). We conduct a reexamination of those observations and demonstrate that there were two waves of dust emanation. It is significant that the two temporal maxima of the Phaethon coma brightness were separated by a noticeable dimming of the coma that can be explained by fast departure of the ejected dust particles from the field of view. This rapid motion necessarily constrains size of dust particles to being of a few micrometers or smaller. Under the assumption of submicron-size dust particles, the total volume of the ejected material can be remarkably small, only ~1 m^3 that is a factor of ~10^5 smaller compared to what was suggested in Jewitt & Li (2010) and ~10^2 smaller compared to that of Jewitt et al. (2013). Such a small ejecta volume can be acquired from a meteoroid with radius of less than 5 cm, striking Phaethon at relative velocity of ≤ 100 km/s. An impact of a series of such small meteoroids on Phaethon when it was ~0.14 au from the Sun does not seem unrealistic.

Journal of Quantitative Spectroscopy and Radiative Transfer (Published)

DOI: 10.1016/j.jqsrt.2022.108224