The House of David

"dawnbreak in the west"

Wednesday, August 24, 2016

Pons-Brooks

Any comet is best visible "when the stars align" - more precisely, if the Earth is at the correct point in the ecliptic when the comet is near the Sun ("perihelion").

I've been tweaking the Pons-Brooks wiki page for the past few weeks. Today I found some Korean records. Apparently this orbit has passed from Aries or Pisces (zodiacal, no surprise) through Cetus toward Eridanus (southward): once in 1313, again in 1668. Now, I don't read Korean myself. But the article gives the key data in Latin numerals and dates - and one of them matches nicely with Western records from (March) 1668. I gather that Pons-Brooks is best visible when the Sun and the comet are both in Aries or Pisces - that is, in March. The comet would at this time have its (southern) perihelion Aprilish, when it sails between Earth and our Sun.

Comets - like Pluto - share space with (much bigger) planets, so their orbits tend to be inclined and eccentric. Comets are to be seen not far from the ecliptic; too far from that, they're too far from the Sun (at "aphelion") and too far from us. 12P/Pons-Brooks happens to run a VERY inclined orbit, so its visible path in our heavens runs nearly north-to-south across the equator. South-to-north on the upswing.

Lisbon being approximately the same latitude as northern Korea, the Korean record drops below the horizon with the Portuguese - but a ship captain in Brasil saw more of it. To my knowledge I am the first to link the 1674 ship's report here with the 1668 Korean chronicle. Yay original research! I hope Wiki's editors don't mind.

Since this comet is faint today (all comets lose ice per stay within the solar snowline), it tends not to be seen at all when its arrival does not coincide with March. The upcoming perihelion 21 April 2024 looks promising though.


posted by Zimri on 16:24 | link | 0 comments

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