1. Discovery

2. Orbit

3. Speculations
     Bonilla's comet    Prehistorical times  

4. Footnotes

5. References

6. External links

As of December 2015 12P/Pons–Brooks has not been identified with any meteor-shower streams.^[1]

Discovery

A comet was observed from Korea from 10 April to June 1313 CE.^[2] Over in China, "in the reign of Jin Tsung, the 2nd year of the epoch Hwang King, 3rd moon, day Ting Wei, a comet appeared in the eastern part of S. D. Tsing". This date is calculated to 13 April 1313. The eastern part of the "S. D. Tsing" corresponds to the stars Mebsuta and Alhena in Gemini: about right-ascension 6h and declination 20°.^[3] In Vietnam "during the third month (of the twenty-first year of the Hu'ng-long reign-period) (28 March to 25 April 1313) a hui comet was seen in the west".^[4] Italian observers noticed a brilliant four-coloured apparition in the west, with two "horns" like the Moon.^[5]

Koreans observed "another" comet over 20 March - 22 May 1668.^[6] This one started from Pisces (~RA 1h, Dec. 30°) and traveled southwest across [western] Cetus toward Eridanus (~RA 5h, Dec. -10°). Again in Vietnam, "on a ky-su'u day of the first month, in the spring of the sixth year (of the Canh-tri reign-period), a mau-than year (8 March 1668) a 'Celestial Flail' star appeared in the northwest direction, measuring five feet and resembling a hui comet'";^[7] this is further noted "in the Astronomical Chapters of the Ch'ing Shi Kao" in China.^[8] A comet was also recorded beginning early March 1668 by Europeans; this appeared in the "Whale" constellation today known as Cetus and likewise traveled to Eridanus.^[9][10]

No historical cometary observation has yet been securely identified with Pons-Brooks for its next perihelion circa 1740, although some would later wonder about the 1742 comet.^[11] In the West a third observation was logged on July 12, 1812, by Jean-Louis Pons. Independently, this comet was later found by Vincent Wisniewski on August 1, and Alexis Bouvard on August 2 the same year. At the time no-one had brought these observations together.

In 1883 a (faint) "fourth" comet was accidentally discovered by William Robert Brooks and later identified as the same object as the 1812. Shortly after its initial discovery it was found to have an orbital period of about 70 years with an error of about 5 years. Johann Franz Encke determined a definitive orbit with a period of 70.68 years. This orbit was used to generate an ephemeris for the 1883-4 return, but searches were unsuccessful, until it was rediscovered by Brooks. This year it traveled from Scheat and Markab in western Pegasus, 13 January 1884; southward (through Pisces) to reach perihelion below Iota and Beta Ceti (~RA 0h, Dec. -10°) around 24 January.^[12]

That February, Daniel Kirkwood tentatively identified Pons-Brooks with the comet of 1313; also with comet-sightings 1240, 1382, 1457, 1529{{refn|group=note|name=second|There were apparently four that year; Kirkwood could make little of any of them.^[13]}} and 1742 (but could not link anything with the expected return 1670).^[11] In 2007, Korean astronomers So-Yeon Park and Jongchul Chae confirmed Pons-Brooks with the observation of 1313, and added that of 1668.^[14]

Orbit

Libration is locked at a 6:1 resonance with Jupiter.^[15] The Tisserand invariant with respect to Jupiter (J) is 0.60.^[16]

With a steep orbital inclination of 74.2° this comet does not spend a lot of time near the ecliptic. The Jet Propulsion Laboratory's (JPL) website shows that between the years 1900 and 2200, that the comet was and will be most significantly perturbed by Saturn on July 29, 1957. At that point it passed within 1.6AU of the giant planet's influence; even this approach had negligible effect.^[24] The comet's orbit appears to be stable between 1740 and 2167, with no strong perturbations by any of the planets.^[25][18]

Kirkwood in 1884 noticed that Pons-Brooks shares elements with De Vico's comet of 1846. He suggested that the latter had calved off Pons-Brooks some centuries prior.^[11] Later he identified the two comets' capture into their elliptical orbits (or their parent body's capture) with their shared aphelion close to Neptune 991 CE.^[19]

Speculations

Bonilla's comet

On August 12-13th of 1883, Mexican astronomer José Bonilla observed 447 bodies cross the solar disc, from an observatory in Zacatecas. Mexican astronomers in 2011 suggested that a comet may have split into several pieces. These objects were estimated to have had a size of between 46 and 1022 meters, and to have passed only 538 to 8062 km from the Earth. They raised Pons-Brooks as one possibility, in which case Earth barely avoided multiple Tunguska events or even a mass extinction.^[29] This was reported in the media October 2011.^[20][21][22]

But the source of these objects could also have been comet C/1883 D1 (Brooks-Swift) or even a third, unknown comet that year. The event also coincided with the annual Perseids meteor shower. Even migrating birds cannot be ruled out.^[29]

Prehistorical times

Chinese historiography records its first comet around 1500 BCE, although long after the fact; traditionally, this "broom-star" heralded the sweeping-away of the tyrannical Xia dynasty (and its replacement with the Shang).^[23]

Footnotes

References

External links

• Comet 12P/Pons-Brooks light curve (Dmitry Chestnov)
• {{JPL small body|name=12P/Pons-Brooks}}

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