Cometary Science Newsletter

June 2020
Michael S. P. Kelley (

Refereed Articles

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

Ionic emissions in comet C/2016 R2 (Pan-STARRS)

  • Kumar Venkataramani 1,2
  • Shashikiran Ganesh 1
  • Kiran S.Baliyan 1
  1. Astronomy & Astrophysics Division, Physical Research Laboratory, Ahmedabad, India
  2. Department of Physics, Leach Science Center, Auburn University, Auburn, AL, USA.

We carried out observations of a peculiar comet, C/2016 R2 (Pan-STARRS), using a low resolution spectrograph mounted on the 1.2m telescope at Mount Abu Infrared Observatory, India. The comet was observed on two dates in January 2018, when it was at a heliocentric distance of 2.8 AU. Study based on our observations revealed that the optical spectrum of this comet is quite unusual as compared to general cometary spectra. Most of the major cometary emissions like C2, C3 and CN were absent in comet C/2016 R2. However, the comet spectrum showed very strong emission bands from ionic species like CO+ and N2+. A mean N2/CO ratio of 0.09 ± 0.02 was derived from the spectra and an extremely low depletion factor of 1.6 ± 0.4 has been estimated for this ratio as compared to the solar nebula. We have also detected minor emission features beyond 5400 Å, albeit marginally. The column densities of CO+ and N2+ were calculated from their emission bands. The optical spectrum suggests that the cometary ice is dominated by CO. The low depletion factor of N2/CO ratio in this comet, as compared to the solar nebula and the unusual spectrum of the comet are consequences of distinctive processing at the location of its formation in the early solar nebula.

Monthly Notices of the Royal Astronomical Society (In press)

DOI: 10.1093/mnras/staa1141 NASA ADS: 2020arXiv200410266V arXiv: 2004.10266

Recurrent Cometary Activity in Near-Earth Object (3552) Don Quixote

  • Michael Mommert 1
  • Joseph L. Hora 2
  • David E. Trilling 3
  • Nicolas Biver 4
  • Kacper Wierzchos 5
  • Olga Harrington Pinto 6
  • Jessica Agarwal 7
  • Yoonyoung Kim 7
  • Andrew McNeill 3
  • Maria Womack 8
  • Matthew M. Knight 9,10
  • David Polishook 11
  • Nick Moskovitz 1
  • Michael S. P. Kelley 9
  • Howard A. Smith 2
  1. Lowell Observatory, 1400 W Mars Hill Rd, Flagstaff, AZ 86001, USA
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138-1516, USA
  3. Department of Astronomy and Planetary Science, Northern Arizona University, P.O. Box 6010, Flagstaff, AZ 86011, USA
  4. LESIA Observatoire de Paris, 5 pl. J. Janssen, F-92190 Meudon, France
  5. Catalina Sky Survey, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
  6. Department of Physics, University of Central Florida, Orlando, FL 32816, USA
  7. Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
  8. Florida Space Institute and Department of Physics, University of Central Florida, Orlando, FL 32816-2385, USA
  9. University of Maryland, 1113 Physical Sciences Complex, Building 415, College Park, MD 20742-2421, USA
  10. Department of Physics, United States Naval Academy, 572C Holloway Rd, Annapolis, MD 21402, USA
  11. Faculty of Physics, Weizmann Institute of Science, Rehovot 0076100, Israel

We report on observations of activity in near-Earth object (3552) Don Quixote using the Spitzer Space Telescope and ground-based telescopes around its 2018 perihelion passage. Spitzer observations obtained six months before perihelion show extended emission around the target's nucleus that is most likely caused by molecular band emission from either CO2 or CO, but we find no significant emission from dust. Ground-based optical observations taken close to perihelion reveal for the first time activity in the optical wavelengths, which we attribute to solar light reflected from dust particles. IRAM millimeter radio observations taken around the same time are unable to rule out CO as the driver of the molecular band emission observed with Spitzer. The comparison of the gas activity presented here with observations performed during Don Quixote's previous apparition suggests that activity in Don Quixote is recurrent. We conclude that (3552) Don Quixote is most likely a weakly active comet.

Planetary Science Journal (Published)

DOI: 10.3847/PSJ/ab8ae5

  • Michael Mommert 1
  • David E. Trilling 2
  • Joseph L. Hora 3
  • Cassandra Lejoly 4
  • Annika Gustafsson 2
  • Matthew Knight 5
  • Nick Moskovitz 1
  • Howard A. Smith 3
  1. Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001, USA
  2. Department of Astronomy and Planetary Science, Northern Arizona University, P.O. Box 6010, Flagstaff, AZ 86011, USA
  3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138-1516, USA
  4. Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85719, USA
  5. University of Maryland, 1113 Physical Sciences Complex, Building 415, College Park, MD 20742-2421, USA

We report on our long-term observational campaign to characterize and monitor a select sample of 75 dynamically selected dormant comet candidates and six near-Sun asteroids. Both asteroid subpopulations can be considered likely to display comet-like activity. Dormant comets are currently inactive comet nuclei that can still harbor volatiles in subsurface layers, whereas near-Sun asteroids have extremely low perihelion distances and are thus prone to catastrophic disruption. As a result of our 4 yr long observing campaign, we find only dormant comet 3552 Don Quixote to show activity during our program. We furthermore find that (51 ± 10)% of dynamically selected dormant comet candidates in near-Earth space have comet-like physical properties, as well as (56 ± 16)% of dynamically selected dormant comet candidates in other parts of the solar system. All of our near-Sun asteroid sample targets are of nonprimitive nature, suggesting that primitive near-Sun asteroids are more likely to disrupt than nonprimitives. We furthermore find a significant fraction of our near-Sun asteroid sample to display extremely blue V–I color indices, potentially hinting at physical alterations of surface material close to the Sun.

Planetary Science Journal (Published)

DOI: 10.3847/PSJ/ab8191 NASA ADS: 2020PSJ.....1...10M

Small Bodies of the Solar System Active at Large Heliocentric Distances: Studies with the 6-Meter Telescope of SAO RAS

  • Ivanova, A. V. 1,2,3
  1. Astronomical Institute of the Slovak Academy of Sciences, Slovak Republic
  2. Main Astronomical Observatory of the National Academy of Science of Ukraine, Ukraine [3] Astronomical Observatory of the Taras Shevchenko National University of Kyiv, Ukraine

A detailed study of comets active at large heliocentric distances (greater than 4 au) which enter the Solar System for the first time and are composed of matter in its elementary, unprocessed state, would help in our understanding of the history and evolution of the Solar System. In particular, contemporary giant planet formation models require the presence of accretion of volatile elements such as neon, argon, krypton, xenon and others, which initially could not survive at the distances where giant planets were formed. Nevertheless, the volatile components could be effectively delivered by the Kuiper-belt and Oort-cloud bodies, which were formed at temperatures below 30 K. This review is dedicated to the results of a multi-year comprehensive study of small bodies of the Solar System showing a comet-like activity at large heliocentric distances. The data were obtained from observations with the 6-m telescope of SAO RAS equipped with multi- mode focal reducers SCORPIO and SCORPIO-2.

Astrophysical Bulletin (Published)

DOI: 10.1134/S1990341320010034 NASA ADS:  2020AstBu..75...31I

Coma Anisotropy and the Rotation Pole of Interstellar Comet 2I/Borisov

  • Kim, Y. 1
  • Jewitt, D. 2
  • Mutchler, M. 3
  • Agarwal, J. 1
  • Hui, M.-T. 4
  • Weaver, H. 5
  1. Max Planck Institute for Solar System Research
  2. UCLA
  3. Space Telescope Science Institute
  4. University of Hawaii
  5. Johns Hopkins University Applied Physics Laboratory

Hubble Space Telescope observations of interstellar comet 2I/Borisov near perihelion show the ejection of large (>~100 um) particles at <~9 m/s speeds, with estimated mass-loss rates of ~35 kg/s. The total mass loss from comet Borisov corresponds to loss of a surface shell on the nucleus only ~0.4 m thick. This shell is thin enough to be susceptible to past chemical processing in the interstellar medium by cosmic rays, meaning that the ejected materials cannot necessarily be considered as pristine. Our high-resolution images reveal persistent asymmetry in the dust coma, best explained by a thermal lag on the rotating nucleus causing peak mass loss to occur in the comet nucleus afternoon. In this interpretation, the nucleus rotates with an obliquity of 30 deg (pole direction R.A. = 205 deg and decl. = 52 deg). The subsolar latitude varied from -35 deg (southern solstice) at the time of discovery to 0 deg (equinox) in 2020 January, suggesting the importance of seasonal effects. Subsequent activity likely results from regions freshly activated as the northern hemisphere is illuminated for the first time.

The Astrophysical Journal Letters (Published)

DOI: 10.3847/2041-8213/ab9228 NASA ADS: 2020arXiv200502468K arXiv: 2005.02468