Cometary Science Newsletter

April 2022
Michael S. P. Kelley (

Post-doctoral opportunity for research on small bodies or planetesimals

The State Key Laboratory of Lunar and Planetary Science at Macau University of Science and Technology (Macau SAR;, invites applications for post-doctoral researchers to work on the field of small solar system bodies, interstellar objects and/or early evolution of planetesimals in protoplanetary disks.

We will offer one or two post-doctoral positions. This project will involve the analysis of astronomical data, simulations of orbital evolution or thermal evolution. Candidates who have experiences in

  1. Observations and related data process; or
  2. Simulation of orbital evolution; or
  3. Hydrodynamic simulation will be given priority.

The appointment will be for a period of at least 24 months, starting on 1st September, or as soon as possible. The salary will be around 20000~25000 MOP per month, and there will be funds for traveling.

Applicants should submit their application to Assistant Prof. Liang-Liang Yu ( by the 30th April 2022. The application should include a CV, an introduction of past work and future research plan, and two recommendation letters.

If you have interest in this job, please do not hesitate to contact us.

Application Deadline: Saturday, April 30, 2022
Current Status of Position: Accepting Applicants

Refereed Articles

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

Size and albedo of the largest detected Oort-cloud object: Comet C/2014 UN271 (Bernardinelli-Bernstein)

  • E. Lellouch 1
  • R. Moreno 1
  • D. Bockelée-Morvan 1
  • N. Biver 1
  • P. Santos-Sanz 2
  1. LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
  2. Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain

The recently announced Oort-cloud comet C/2014 UN271 (Bernardinelli-Bernstein) is remarkable in at least three respects: (i) it was discovered inbound as far as ∼29 au from the Sun (with prediscovery images up to ∼34 au); (ii) it already showed cometary activity at almost 24 au; and (iii) its nuclear magnitude (Hr ∼ 8.0) indicates an exceptionally large object. Detection of gases is expected in the upcoming years as the comet heads toward a perihelion of ∼11 au in 2031. The goal is to determine the object’s diameter and albedo from thermal measurements. We used ALMA in extended configuration (resolution ∼0.064″) to measure the 1287 μm (233 GHz) continuum flux of the comet. Observations were performed on August 8, 2021, at a 20.0 au distance from the Sun. The high spatial resolution was chosen in order to filter out any dust contribution. We also used a recently published Afρ value to estimate the dust production rate and the expected dust thermal signal for various assumptions on particle size distribution. We detected the thermal emission of the object at ∼10σ, with a flux of 0.128 ± 0.012 mJy. Based on observational constraints and our theoretical estimates of the dust contribution, the entirety of the measured flux can be attributed to the nucleus. From NEATM modeling combined with the Hr magnitude, we determine a surface-equivalent diameter of 137 ± 17 km and a red geometric albedo of 5.3 ± 1.2%. This confirms that C/2014 UN271 is by far the largest Oort-cloud object ever found (almost twice as large as comet C/1995 O1 Hale-Bopp) and, except for the Centaur 95P/Chiron, which shows outburst-like activity, the largest known comet in the Solar System. On the other hand, the C/2014 UN271 albedo is typical of comets, adding credence to a “universal” comet nucleus albedo. With its distant perihelion and uniquely large size, C/2014 UN271 (Bernardinelli-Bernstein) is the prominent archetype of distant comets whose activity is driven by hypervolatiles. Monitoring of dust and gas emission as the comet approaches and passes perihelion will permit its activity time pattern to be studied and compared to the distant (outbound) activity of Hale-Bopp. Post-perihelion thermal measurements will permit the study of possible albedo changes, such as a surface brightening compared to pre-perihelion, as was observed for Hale-Bopp.

Astronomy & Astrophysics (Letters) (Published)

DOI: 10.1051/0004-6361/202243090 NASA ADS: 2022A&A...659L...1L arXiv: 2201.13188