C/2014 UN<inf>271</inf>(Bernardinelli-Bernstein): The Nearly Spherical Cow of Comets
Authors
Allam, S
Andrade-Oliveira, F
Avila, S
Burke, DL
Carnero Rosell, A
Kind, MC
Da Costa, LN
Pereira, MES
De Vicente, J
Everett, S
Ferrero, I
Flaugher, B
Frieman, J
Gruen, D
Gutierrez, G
Honscheid, K
James, DJ
Kuropatkin, N
Lahav, O
Maia, MAG
Ogando, RLC
Malagón, AAP
Rodriguez-Monroy, M
Romer, AK
Sanchez, E
Schubnell, M
Serrano, S
Smith, M
Soares-Santos, M
Suchyta, E
Troxel, MA
Varga, TN
Walker, AR
Zhang, Y
Publication Date
2021-11Journal Title
Astrophysical Journal Letters
ISSN
2041-8205
Publisher
American Astronomical Society
Volume
921
Issue
2
Language
en
Type
Article
This Version
VoR
Metadata
Show full item recordCitation
Bernardinelli, P., Bernstein, G., Montet, B., Weryk, R., Wainscoat, R., Aguena, M., Allam, S., et al. (2021). C/2014 UN<inf>271</inf>(Bernardinelli-Bernstein): The Nearly Spherical Cow of Comets. Astrophysical Journal Letters, 921 (2) https://doi.org/10.3847/2041-8213/ac32d3
Abstract
C/2014 UN271 (Bernardinelli-Bernstein) is a comet incoming from the Oort
cloud which is remarkable in having the brightest (and presumably largest)
nucleus of any well-measured comet, and having been discovered at heliocentric
distance $r_h\approx29$ au farther than any Oort-cloud member. We describe the
properties that can be inferred from images recorded until the first reports of
activity in June 2021. The orbit has $i=95^\circ,$ with perihelion of 10.97 au
to be reached in 2031, and previous aphelion at $40,400\pm260$ au. Backwards
integration of the orbit under a standard Galactic tidal model and known
stellar encounters suggests this is a pristine new comet, with a perihelion of
$q\approx18$ au on its previous perihelion passage 3.5 Myr ago. The photometric
data show an unresolved nucleus with absolute magnitude $H_r=8.0,$ colors that
are typical of comet nuclei or Damocloids, and no secular trend as it traversed
the range 34--23 au. For $r$-band geometric albedo $p_r,$ this implies a
diameter of $150 (p_r/0.04)^{-0.5}$ km. There is strong evidence of brightness
fluctuations at $\pm0.2$ mag level, but no rotation period can be discerned. A
coma consistent with a ``stationary' $1/\rho$ surface-brightness distribution
grew in scattering cross-section at an exponential rate from $A f \rho\approx1$
m to $\approx150$ m as the comet approached from 28 to 20 au. The activity is
consistent with a simple model of sublimation of a surface species in radiative
equilibrium with the Sun. The inferred enthalpy of sublimation matches those of
$CO_2$ and $NH_3$. More-volatile species -- $N_2,$ $CH_4,$ and $CO$ -- must be
far less abundant on the sublimating surfaces.
Sponsorship
National Science Foundation (NSF) (AST-1515804)
National Science Foundation (NSF) (AST-2009210)
U.S. Department of Energy (DOE) (DE-SC0007901)
Identifiers
apjlac32d3, ac32d3, aas34873
External DOI: https://doi.org/10.3847/2041-8213/ac32d3
This record's URL: https://www.repository.cam.ac.uk/handle/1810/330492
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
Statistics
Total file downloads (since January 2020). For more information on metrics see the
IRUS guide.