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16P/Brooks 2

Past, Present, and Future Orbits by Kazuo Kinoshita

NEAT image of 16P exposed on 2001 December 17
Copyright © 2001 by Near Earth Asteroid Tracking (NEAT)

This image was obtained by the Near Earth Asteroid Tracking (NEAT) program using the 48-inch Oschin telescope and a CCD camera. The image was exposed on 2001 December 17.26, for about 2.5 minutes.


     William R. Brooks (Geneva, New York) was sweeping for comets on the morning of 1889 July 7, when he found this comet in the southeastern sky within the constellation Aquarius. He described it as faint, with a coma 1 arc minute across and a tail 10 arc minutes long. Although he was unable to detect any motion before sunrise, Brooks quickly found the comet the next morning and noted it had moved slightly northward.

Historical Highlights

  • The comet steadily brightened after discovery as it approached both the sun and Earth. But with the brightening came surprises. On August 1, E. E. Barnard spotted two small, nebulous companions located 1 and 4.5 arc minutes away. The next night, Barnard saw four or five additional nebulous objects, all of which were absent on August 3. On August 4, Barnard saw two more objects. The main nucleus was labelled "A", while those seen on August 1 were labelled "B" and "C". The two objects seen on August 4 were labelled "D" and "E". Companion "E" was not seen after the 4th, while "D" remained visible for about a week. By mid-August "B" suddenly began to grow large and diffuse and it was last seen on September 5. Companion "C" remained observable until November 26, while the main nucleus, "A", remained visible nearly until the time the comet was last seen, which was 1891 January 13.
  • Another interesting aspect of this comet's first apparition was that it attained a maximum magnitude of 8. Despite a smaller perihelion distance in the 20th century, the comet has never become brighter than magnitude 10.5. This abnormal brightening, and the fact that the comet split into multiple pieces, is blamed on the planet Jupiter. It would seem the comet passed only 0.001 AU from Jupiter in 1886, actually spending two days within the orbit of Jupiter's moon Io. The gravitational stresses apparently shattered the comet, revealing fresh surfaces to interact with the sun's radiation at the 1889 apparition. In addition to the comet never having attained this brightness since 1889, no trace of any of the other nuclei have ever been present at later returns.
  • Since the comet's discovery apparition, there has been little to get excited about. It has been missed only twice, in 1918 and 1967, when the sun-Earth-comet geometry was especially bad, and an encounter with Jupiter in 1921, decreased the perihelion distance from 1.96 AU to 1.86 AU.
  • cometography.com