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  C/2014 UN271 (Bernardinelli-Bernstein): The nearly spherical cow of comets

Bernardinelli, P. H., Bernstein, G. M., Montet, B. T., Weryk, R., Wainscoat, R., Aguena, M., et al. (2021). C/2014 UN271 (Bernardinelli-Bernstein): The nearly spherical cow of comets. The Astrophysical Journal Letters, 921(2): L37. doi:10.3847/2041-8213/ac32d3.

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Bernardinelli, Pedro H., Author
Bernstein, Gary M., Author
Montet, Benjamin T., Author
Weryk, Robert, Author
Wainscoat, Richard, Author
Aguena, M., Author
Allam, S., Author
Andrade-Oliveira, F., Author
Annis, J., Author
Avila, S., Author
Bertin, E., Author
Brooks, D., Author
Burke, D. L., Author
Rosell, A. Carnero, Author
Kind, M. Carrasco, Author
Carretero, J., Author
Cawthon, R., Author
Conselice, C., Author
Costanzi, M., Author
da Costa, L. N., Author
Pereira, M. E. S., AuthorVicente, J. De, AuthorDiehl, H. T., AuthorEverett, S., AuthorFerrero, I., AuthorFlaugher, B., AuthorFrieman, J., AuthorGarcía-Bellido, J., AuthorGaztanaga, E., AuthorGerdes, D. W., AuthorGruen, D., AuthorGruendl, R. A., AuthorGschwend, J., AuthorGutierrez, G., AuthorHinton, S. R., AuthorHollowood, D. L., AuthorHonscheid, K., AuthorJames, D. J., AuthorKuehn, K., AuthorKuropatkin, N., AuthorLahav, O., AuthorMaia, M. A. G., AuthorMarshall, J. L., AuthorMenanteau, F., AuthorMiquel, R., AuthorMorgan, R., AuthorOgando, R. L. C., AuthorPaz-Chinchón, F., AuthorPieres, A., AuthorMalagón, A. A. Plazas, AuthorRodriguez-Monroy, M., AuthorRomer, A. K., AuthorRoodman, A., AuthorSanchez, E., AuthorSchubnell, M., AuthorSerrano, S., AuthorSevilla-Noarbe, I., AuthorSmith, M., AuthorSoares-Santos, M., AuthorSuchyta, E., AuthorSwanson, M. E. C., AuthorTarle, G., AuthorTo, C., AuthorTroxel, M. A., AuthorVarga, T. N.1, Author           Walker, A. R., AuthorZhang, Y., Author more..
1Optical and Interpretative Astronomy, MPI for Extraterrestrial Physics, Max Planck Society, ou_159895              


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 Abstract: Comet C/2014 UN271 (Bernardinelli-Bernstein), incoming from the Oort cloud, is remarkable in having the brightest (and presumably largest) nucleus of any well-measured comet and having been discovered at the heliocentric distance rh ≈ 29 au, farther than any Oort cloud comet. In this work, we describe the discovery process and observations and the properties that can be inferred from images recorded until the first reports of activity in 2021 June. The orbit has i = 95°, with a perihelion of 10.97 au to be reached in 2031 and a previous aphelion at 40,400 ± 260 au. Backward integration of the orbit under a standard Galactic tidal model and known stellar encounters suggests a perihelion of q ≈ 18 au on its previous perihelion passage 3.5 Myr ago; hence, the current data could be the first ever obtained of a comet that has not been inside Uranus's orbit in 4 Gyr. The photometric data show an unresolved nucleus with absolute magnitude Hr = 8.0, colors that are typical of comet nuclei or Damocloids, and no secular trend as it traversed the range 34–23 au. For the r-band geometric albedo pr, this implies a diameter of 150 (pr 0.04)-0.5 km. There is strong evidence of brightness fluctuations at the ±0.2 mag level, but no rotation period can be discerned. A coma, nominally consistent with a "stationary" 1/ρ surface brightness distribution, grew in scattering cross section at an exponential rate from Afρ ≈ 1 to ≈150 m as the comet approached from 28 to 20 au. The activity rate is consistent with a very simple model of sublimation of a surface species in radiative equilibrium with the Sun. The inferred enthalpy of sublimation matches those of CO2 and NH3. More volatile species, such as N2, CH4, and CO, must be far less abundant on the sublimating surfaces.


Language(s): eng - English
 Dates: 2021-11-09
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.3847/2041-8213/ac32d3
 Degree: -



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Title: The Astrophysical Journal Letters
  Other : Astrophys. J. Lett.
Source Genre: Journal
Publ. Info: Chicago, IL : University of Chicago Press for the American Astronomical Society
Pages: - Volume / Issue: 921 (2) Sequence Number: L37 Start / End Page: - Identifier: ISSN: 0004-637X
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215