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12P/Pons-Brooks

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     Jean Louis Pons (Marseille, France) discovered this comet on 1812 July 21.07 UT. He said it was located in Lynx. Pons described it as a small, ill-defined nebulosity, without a tail, and not visible to the naked eye. Independent discoveries were made by Wisniewsky (Russia) on August 1 and Bouvard (France) on August 2.
      William R. Brooks (Phelps, New York) accidentally discovered this comet on 1883 September 2 while searching for comets. He described it as small and estimated the magnitude as 10.

Historical Highlights

  • During the discovery apparition the comet first became visible to the naked eye on August 13, and by the end of August it was displaying a tail about 2 degrees long. Although magnitude estimates were not made at this time, the comet probably reached its maximum brightness around mid-September, with a magnitude around 4. The comet was last seen on September 28 as its southern motion took it out of sight below the southern horizon.
  • Following the comet's appearance several attempts were made to determine its orbit and astronomers quickly agreed that the orbit was a short-period one. Estimates of the orbit period ranged from 65 to 75 years. Johann Encke determined a definitive orbit with a period of 70.68 years. This orbit was used to generate an ephemeris for the 1883 return, but searches were unsuccessful. As noted above, the comet was accidentally discovered by Brooks in September.
  • The comet was easily seen by astronomers following its 1883 "discovery", yet it remained a small, tailless nebulosity. But observations on September 23 revealed a rapid, unusual change had occurred as the comet had become a stellar object of magnitude 7 or 8. Thereafter, the coma reappeared, in addition to a short tail. The comet went back to normal and continued its expected brightening. It attained naked-eye visibility on November 20 and as January began it reached its greatest brightness of magnitude 3. Interestingly, Muller (Germany) noted a 0.7-magnitude brightening of the nucleus during 1.75 hours on January 1 and several astronomers reported the comet brightened by one magnitude on January 19. The comet steadily faded thereafter and was last seen on June 2 at magnitude 9.5.
  • Several orbit revisions were made after the 1883-4 apparition and a prediction that the comet would next reach perihelion on1954 May 27 was published by P. Herget and P. Musen in 1953. Elizabeth Roemer (Lick Observatory) used their ephemeris and recovered the comet on 1953 June 20 at a magnitude of 17.5. The comet was only 25 arc minutes from the predicted position. As with the 1883-4 apparition, the comet experienced several outbursts in brightness. The first on July 1 brought the comet up to magnitude 13. The comet was back to its predicted brightness of 18 by July 16 and a slow brightening set in as the comet approached perihelion. By September 15 the comet had finally reached magnitude 16, but another outburst kicked in and took the comet up to magnitude 12 by the 28th. Another outburst in occurred in December and then the comet performed as expected thereafter. It reached its maximum magnitude of 6 during late April.
  • The comet's orbit is very stable during the period of 1740 to 2167, with insignificant alterations by any of the planets. In fact, the closest the comet has come to any planet during that period was 0.634 AU from Earth on 1884 January 9. Earth's gravity had a negligible effect on the comet's motion.
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