https://arxiv.org/pdf/2109.09852.pdf##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 \approx 29 \;\operatorname{au}##, farther than any Oort-cloud member. We describe in this work the discovery process and observations, and the properties that can be inferred from images recorded until the first reports of activity in June ##2021.## The orbit has ## i = 95°##, with perihelion of ##10.97\;\operatorname{au}## to be reached in ##2031,## and previous aphelion at ##40, 400 \pm 260\;\operatorname{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 \approx 18\;\operatorname{au}## on its previous perihelion passage ##3.5\;\operatorname{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\;\operatorname{au}##. For ##r##-band geometric albedo ##p_r##, this implies a diameter of ##150\,(p_r/0.04)−0.5 \;\operatorname{km}.## There is strong evidence of brightness fluctuations at ##\pm 0.2## mag level, but no rotation period can be discerned. A coma, nominally consistent with a "stationary" ##1/\rho## surface-brightness distribution, grew in scattering cross-section at an exponential rate from ##Afρ \approx 1\; m## to ##\approx 150\; m## as the comet approached from ##28## to ##20\;\operatorname{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 ##CO_2## and ##NH_3##. More-volatile species such as ##N_2##, ##CH_4##, and ##CO## must be far less abundant on the sublimating surfaces.
Comet Bernardinelli-Bernstein is a newly discovered comet that was first observed in June 2021 by the Dark Energy Survey collaboration. It is estimated to have a diameter of 100-200 kilometers and is currently located in the outer solar system.
Comet Bernardinelli-Bernstein's entry into the inner solar system is significant because it will be passing close to the Sun and potentially becoming visible to the naked eye. This allows scientists to study the comet's composition and behavior up close, providing valuable insights into the formation and evolution of our solar system.
According to current predictions, Comet Bernardinelli-Bernstein will not come close enough to Earth to pose any threat. Its closest approach to Earth will be on January 22, 2031, at a distance of approximately 10.7 astronomical units (AU), which is equivalent to about 1 billion miles.
Based on its current trajectory, Comet Bernardinelli-Bernstein is expected to pass through the inner solar system and make its closest approach to the Sun on January 23, 2031, at a distance of approximately 10.9 million kilometers. It will then continue its journey back into the outer solar system.
It is possible that Comet Bernardinelli-Bernstein will become visible to the naked eye as it approaches the Sun, but this cannot be guaranteed. Its brightness will depend on various factors, such as its size, composition, and how much it is affected by solar radiation and outgassing. Astronomers will continue to monitor the comet's behavior to make more accurate predictions about its visibility.