Diameter and rotational period of Comet C/2014 UN271 (Bernardinelli-Bernstein)

ATel #15356; I. Ferrin (Institute of Physics, University of Antioquia, Medellin, Colombia); A. Herrero (Valencian International University, Valencia, Spain)
on 29 Apr 2022; 21:54 UT
Credential Certification: Ignacio Ferrin (ignacio.ferrin@udea.edu.co)

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We have characterized comet C/2014 UN271 (Bernardinelli-Bernstein), using observations provided by the Minor Planet Center, by means of the Secular Light Curves (SLC) method proposed by Ferrin (2009; 2010). 1. The comet turn on at a distance of RON=-23.5±0.4 AU pre-perihelion, compatible with the result obtained by Farnham (ATel #14759). 2. The analysis of the nuclear phase presents an average magnitude mnuc(1,1,0) = 7.90±0.25, and assuming an albedo of 5.3%±1.2 (Lellouch et al, 2022), allows us to calculate its diameter DEFFE = 153±18 km. 3. The nuclear phase presents rotational periodicity with a period PROT=20.6±0.2 days. Its rotational light curve has an amplitude of 0.50±0,1 mag, which gives us information about the geometry of the comet. This amplitude corresponds to a ratio of axis a/b=1.26±0.11. 4. After the analysis of the rotational light curve by means of a moving average, a well-localized zone of activity is shown, and its cause may be the existence of a pocket of carbon dioxide or carbon monoxide (CO2, CO) within a matrix of water ice (H2O). 5. The limited number of observations that we have, due to the distance of the comet (it still has 9 years left to reach its perihelion) does not allow us to carry out the complete SLC. For this reason, it has been estimated taking as reference the SLC of comet C/1995 O1 (Hale-Bopp). This estimate has allowed the calculation of the cometary age P-AGE = 1.6±0.3 cometary years (cy), classifying it as a baby comet (Ferrín, 2009; 2010). For comparison, the age of comet Hale-Bopp is 2.4±0.2 cy. The evidence that we have presented will be expanded and discussed in a future publication. References: - Ferrin, I. (2010). Atlas of secular light curves of comets. Planetary and Space Science, 58(3), 365-391. - Ferrin, I. (2009). Secular light curves of comets. Proceedings of the International Astronomical Union, 5(S263), 263-268. - Lellouch, E., Moreno, R., Bockelee-Morvan, D., Biver, N., & Santos-Sanz, P. (2022). Size and albedo of the largest detected Oort-cloud object: Comet C/2014 UN 271 (Bernardinelli-Bernstein). Astronomy & Astrophysics. C/2014 UN 271 (Bernardinelli-Bernstein). Astronomy & Astrophysics.