Paper detail

New orbit recalculations of comet C/1890 F1 Brooks and its dynamical evolution

C/1890 F1 Brooks belongs to a group of nineteen comets used by Jan Oort to support his famous hypothesis on the existence of a spherical cloud containing hundreds of billions of comets with orbits of semimajor axes between 50 and 150 thousand au. Comet Brooks stands out from this group because of a long series of astrometric observations as well as nearly two-year long observational arc. Rich observational material makes this comet an ideal target for testing the rationality of an effort to recalculate astrometric positions on the basis of original (comet-star)-measurements using modern star catalogues. This paper presents the results of such new analysis based on two different methods: (i) automatic re-reduction based on cometary positions and the (comet-star)-measurements, and (ii) partially automatic re-reduction based on the contemporary data for originally used reference stars. We show that both methods offer a significant reduction of orbital elements uncertainties. Based on the most preferred orbital solution, the dynamical evolution of comet Brooks during three consecutive perihelion passages is discussed. We conclude that C/1890 F1 is a dynamically old comet that passed the Sun at a distance below 5 au during its previous perihelion passage. Furthermore, its next perihelion passage will be a little closer than during the 1890-1892 apparition. C/1890 F1 is interesting also because it suffered extremely small planetary perturbations when it travelled through the planetary zone. Therefore, in the next passage through perihelion it will be once again a comet from the Oort spike.