Cometcountdown

12P/Pons-Brooks
Discovered by
Jean-Louis Pons William Robert Brooks
Discovery date
12 July, 1812
Semi-major axis
17.1212 AU
Eccentricity
0.95481
Orbital period
70.85
Inclination
74.176°
Epoch
15 September, 1954
Aphelion
33.468 AU
Perihelion
0.77366 AU
Last Perihelion(s)
22 May, 1954 - 25 January, 1884 - 15 September, 1812 - 10 March, 1668
Next Perihelion
21 April, 2024

Orbit

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

Orbital evolution... from 1585 to 2406. Top: comet's trajectories in a frame centred on Jupiter and rotating with it around the Sun. Centre: plots of the osculating period (in units of Jupiter's period); the plots extend from -0.5 to +0.5 around the exact resonance. Bottom: polar diagram of the osculating period (radius vectors) and the heliocentric elongation of Jupiter from the comet (at perihelion of the latter, position angles).

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. 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.

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. This was reported in the media October 2011. 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.

 

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). In Egypt, the so-called "Tulli Papyrus" (of dubious provenance) records a "disk of fire" for the third month of the 22nd year of Tuthmosis III (1486 BCE by one chronology). Freelance historical researcher Graham Phillips links these to Pons-Brooks and suggests it may have inspired the rise of a number of new religions around the world.[29][undue weight? – discuss] This is however difficult to reconcile with Kirkwood's thesis of 1886, which if true means that the comet's orbit cannot be extrapolated (and was likely parabolic) prior to 991 CE.

Last modified
12/12/2016 - 02:48