C/1906 B1 Brooks
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Comet C/1906 B1 was discovered on 27 January 1906 by William Robert Brooks (Smith Observatory at Hobart College, Geneva, New York, USA). At the moment of discovery the comets was over a month after perihelion passage, and was last seen on 25 April 1906. In 2005, Gary W. Kronk identified a prediscovery observation of this comet performed by E.E. Barnard (Yerkes Observatory, Wisconsin, USA) on 23 July 1905. [Kronk, Cometography: Volume 3].
This comet made its closest approach to the Earth on 11 February 1906 (0.911 au), that is about two weeks after its discovery.
Solutions given here are based on data spanning over 0.756 yr in a range of heliocentric distances from 2.496 au through perihelion (1.297 au) to 2.185 au.
Pure gravitational orbit determined from all available positional measurements (267 observations) give hyperbolic original barycentric orbit (2a-class orbit); also original orbit given in Minor Planet Center is hyperbolic (186 obs. used, the same arc of data; 1B-class orbit, see MPC).
It was possible to obtain the non-gravitational orbit for C/1906 B1 (preferred orbit); however, only radial non-gravitational parameter was determined. This NG solution give elliptical original barycentric orbit (see NG orbit).
Comet suffers rather small planetary perturbations during its passage through the planetary system; however, they lead to escape the comet from the planetary zone on a hyperbolic orbit (see future barycentric orbit given for NG solution).
This comet was in the original sample of 19 comets used by Oort for his hypothesis on LPCs; however, according to presented here statistics for previous perihelion passage this comet most probably is dynamically old.
More details in Królikowska et al. 2014.

solution description
number of observations 267
data interval 1905 07 23 – 1906 04 25
data type significantly more measurements after perihelion (POST+)
data arc selection entire data set (STD)
range of heliocentric distances 2.5 au – 1.30 au (perihelion) – 2.18 au
type of model of motion NS - non-gravitational orbits for standard g(r)
data weighting YES
number of residuals 449
RMS [arcseconds] 3.05
orbit quality class 2a
orbital elements (barycentric ecliptic J2000)
Epoch 1606 01 02
perihelion date 1905 12 22.17303526 ± 0.00140805
perihelion distance [au] 1.29627992 ± 0.00004430
eccentricity 0.99984792 ± 0.00009574
argument of perihelion [°] 89.843280 ± 0.002420
ascending node [°] 287.549903 ± 0.000595
inclination [°] 126.512022 ± 0.000192
recip semi-major axis [10-6 au-1] 117.32 ± 73.86
file containing 5001 VCs swarm
1906b1n6.bmi
Time distribution of positional observations with corresponding heliocentric (red curve) and geocentric (green curve) distance at which they were taken. The horizontal dotted line shows the perihelion distance for a given comet whereas vertical dotted line – the moment of perihelion passage
Six 2D-projections of the 6D space of original swarm including 5001 VCs. Each density map is given in logarithmic scale presented on the right in the individual panel.