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

DES Collaboration; Pedro H. Bernardinelli; Gary M. Bernstein; Benjamin T. Montet; Robert Weryk; Richard Wainscoat; M. Aguena; S. Allam; F. Andrade-Oliveira; J. Annis; S. Avila; E. Bertin; D. Brooks; D. L. Burke; A. Carnero Rosell; M. Carrasco Kind; J. Carretero; R. Cawthon; C. Conselice; M. Costanzi; L. N. da Costa; M. E. S. Pereira; J. De Vicente; H. T. Diehl; S. Everett; I. Ferrero; B. Flaugher; J. Frieman; J. García-Bellido; E. Gaztanaga; D. W. Gerdes; D. Gruen; R. A. Gruendl; J. Gschwend; G. Gutierrez; S. R. Hinton; D. L. Hollowood; K. Honscheid; D. J. James; K. Kuehn; N. Kuropatkin; O. Lahav; M. A. G. Maia; J. L. Marshall; F. Menanteau; R. Miquel; R. Morgan; R. L. C. Ogando; F. Paz-Chinchón; A. Pieres; A. A. Plazas Malagón; M. Rodriguez-Monroy; A. K. Romer; A. Roodman; E. Sanchez; M. Schubnell; S. Serrano; I. Sevilla-Noarbe; M. Smith; M. Soares-Santos; E. Suchyta; M. E. C. Swanson; G. Tarle; C. To; M. A. Troxel; T. N. Varga; A. R. Walker; Y. Zhang

doi:10.3847/2041-8213/ac32d3

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

DES Collaboration, Pedro H. Bernardinelli, Gary M. Bernstein, Benjamin T. Montet, Robert Weryk, Richard Wainscoat, M. Aguena, S. Allam, F. Andrade-Oliveira, J. Annis, S. Avila, E. Bertin, D. Brooks, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, R. Cawthon, C. Conselice, M. CostanziL. N. da Costa, M. E. S. Pereira, J. De Vicente, H. T. Diehl, S. Everett, I. Ferrero, B. Flaugher, J. Frieman, J. García-Bellido, E. Gaztanaga, D. W. Gerdes, D. Gruen, R. A. Gruendl, J. Gschwend, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, N. Kuropatkin, O. Lahav, M. A. G. Maia, J. L. Marshall, F. Menanteau, R. Miquel, R. Morgan, R. L. C. Ogando, F. Paz-Chinchón, A. Pieres, A. A. Plazas Malagón, M. Rodriguez-Monroy, A. K. Romer, A. Roodman, E. Sanchez, M. Schubnell, S. Serrano, I. Sevilla-Noarbe, M. Smith, M. Soares-Santos, E. Suchyta, M. E. C. Swanson, G. Tarle, C. To, M. A. Troxel, T. N. Varga, A. R. Walker, Y. Zhang

Australian Astronomical Optics

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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 r_h ≈ 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 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 the r-band geometric albedo p_r, this implies a diameter of 150(p_r/0.04)^-0.5km. 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.

Original language	English
Article number	L37
Pages (from-to)	1-14
Number of pages	14
Journal	Astrophysical Journal Letters
Volume	921
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/ac32d3
Publication status	Published - 10 Nov 2021

Bibliographical note

© 2021. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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DES Collaboration, Bernardinelli, P. H., Bernstein, G. M., Montet, B. T., Weryk, R., Wainscoat, R., Aguena, M., Allam, S., Andrade-Oliveira, F., Annis, J., Avila, S., Bertin, E., Brooks, D., Burke, D. L., Carnero Rosell, A., Kind, M. C., Carretero, J., Cawthon, R., Conselice, C., ... Zhang, Y. (2021). C/2014 UN₂₇₁(Bernardinelli-Bernstein): the nearly spherical cow of comets. Astrophysical Journal Letters, 921(2), 1-14. Article L37. https://doi.org/10.3847/2041-8213/ac32d3

@article{e4cc59b01fc84bf68c39366b9054f975,

title = "C/2014 UN271(Bernardinelli-Bernstein): the nearly spherical cow of comets",

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.",

author = "{DES Collaboration} and Bernardinelli, {Pedro H.} and Bernstein, {Gary M.} and Montet, {Benjamin T.} and Robert Weryk and Richard Wainscoat and M. Aguena and S. Allam and F. Andrade-Oliveira and J. Annis and S. Avila and E. Bertin and D. Brooks and Burke, {D. L.} and {Carnero Rosell}, A. and Kind, {M. Carrasco} and J. Carretero and R. Cawthon and C. Conselice and M. Costanzi and {da Costa}, {L. N.} and Pereira, {M. E. S.} and {De Vicente}, J. and Diehl, {H. T.} and S. Everett and I. Ferrero and B. Flaugher and J. Frieman and J. Garc{\'i}a-Bellido and E. Gaztanaga and Gerdes, {D. W.} and D. Gruen and Gruendl, {R. A.} and J. Gschwend and G. Gutierrez and Hinton, {S. R.} and Hollowood, {D. L.} and K. Honscheid and James, {D. J.} and K. Kuehn and N. Kuropatkin and O. Lahav and Maia, {M. A. G.} and Marshall, {J. L.} and F. Menanteau and R. Miquel and R. Morgan and Ogando, {R. L. C.} and F. Paz-Chinch{\'o}n and A. Pieres and Malag{\'o}n, {A. A. Plazas} and M. Rodriguez-Monroy and Romer, {A. K.} and A. Roodman and E. Sanchez and M. Schubnell and S. Serrano and I. Sevilla-Noarbe and M. Smith and M. Soares-Santos and E. Suchyta and Swanson, {M. E. C.} and G. Tarle and C. To and Troxel, {M. A.} and Varga, {T. N.} and Walker, {A. R.} and Y. Zhang",

note = "{\textcopyright} 2021. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.",

year = "2021",

month = nov,

day = "10",

doi = "10.3847/2041-8213/ac32d3",

language = "English",

volume = "921",

pages = "1--14",

journal = "Astrophysical Journal Letters",

issn = "2041-8205",

publisher = "Institute of Physics Publishing",

number = "2",

}

DES Collaboration, Bernardinelli, PH, Bernstein, GM, Montet, BT, Weryk, R, Wainscoat, R, Aguena, M, Allam, S, Andrade-Oliveira, F, Annis, J, Avila, S, Bertin, E, Brooks, D, Burke, DL, Carnero Rosell, A, Kind, MC, Carretero, J, Cawthon, R, Conselice, C, Costanzi, M, da Costa, LN, Pereira, MES, De Vicente, J, Diehl, HT, Everett, S, Ferrero, I, Flaugher, B, Frieman, J, García-Bellido, J, Gaztanaga, E, Gerdes, DW, Gruen, D, Gruendl, RA, Gschwend, J, Gutierrez, G, Hinton, SR, Hollowood, DL, Honscheid, K, James, DJ, Kuehn, K, Kuropatkin, N, Lahav, O, Maia, MAG, Marshall, JL, Menanteau, F, Miquel, R, Morgan, R, Ogando, RLC, Paz-Chinchón, F, Pieres, A, Malagón, AAP, Rodriguez-Monroy, M, Romer, AK, Roodman, A, Sanchez, E, Schubnell, M, Serrano, S, Sevilla-Noarbe, I, Smith, M, Soares-Santos, M, Suchyta, E, Swanson, MEC, Tarle, G, To, C, Troxel, MA, Varga, TN, Walker, AR & Zhang, Y 2021, 'C/2014 UN₂₇₁(Bernardinelli-Bernstein): the nearly spherical cow of comets', Astrophysical Journal Letters, vol. 921, no. 2, L37, pp. 1-14. https://doi.org/10.3847/2041-8213/ac32d3

TY - JOUR

T1 - C/2014 UN271(Bernardinelli-Bernstein)

T2 - the nearly spherical cow of comets

AU - DES Collaboration

AU - Bernardinelli, Pedro H.

AU - Bernstein, Gary M.

AU - Montet, Benjamin T.

AU - Weryk, Robert

AU - Wainscoat, Richard

AU - Aguena, M.

AU - Allam, S.

AU - Andrade-Oliveira, F.

AU - Annis, J.

AU - Avila, S.

AU - Bertin, E.

AU - Brooks, D.

AU - Burke, D. L.

AU - Carnero Rosell, A.

AU - Kind, M. Carrasco

AU - Carretero, J.

AU - Cawthon, R.

AU - Conselice, C.

AU - Costanzi, M.

AU - da Costa, L. N.

AU - Pereira, M. E. S.

AU - De Vicente, J.

AU - Diehl, H. T.

AU - Everett, S.

AU - Ferrero, I.

AU - Flaugher, B.

AU - Frieman, J.

AU - García-Bellido, J.

AU - Gaztanaga, E.

AU - Gerdes, D. W.

AU - Gruen, D.

AU - Gruendl, R. A.

AU - Gschwend, J.

AU - Gutierrez, G.

AU - Hinton, S. R.

AU - Hollowood, D. L.

AU - Honscheid, K.

AU - James, D. J.

AU - Kuehn, K.

AU - Kuropatkin, N.

AU - Lahav, O.

AU - Maia, M. A. G.

AU - Marshall, J. L.

AU - Menanteau, F.

AU - Miquel, R.

AU - Morgan, R.

AU - Ogando, R. L. C.

AU - Paz-Chinchón, F.

AU - Pieres, A.

AU - Malagón, A. A. Plazas

AU - Rodriguez-Monroy, M.

AU - Romer, A. K.

AU - Roodman, A.

AU - Sanchez, E.

AU - Schubnell, M.

AU - Serrano, S.

AU - Sevilla-Noarbe, I.

AU - Smith, M.

AU - Soares-Santos, M.

AU - Suchyta, E.

AU - Swanson, M. E. C.

AU - Tarle, G.

AU - To, C.

AU - Troxel, M. A.

AU - Varga, T. N.

AU - Walker, A. R.

AU - Zhang, Y.

N1 - © 2021. The Author(s). Published by the American Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

PY - 2021/11/10

Y1 - 2021/11/10

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85120653655&partnerID=8YFLogxK

U2 - 10.3847/2041-8213/ac32d3

DO - 10.3847/2041-8213/ac32d3

M3 - Article

AN - SCOPUS:85120653655

SN - 2041-8205

VL - 921

SP - 1

EP - 14

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L37

ER -

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

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