closestApproachfunction

When two bodies come closest in a span, and how close: the span is scanned in coarse steps (the fastest body goes round forty times in the step, at most two days), then the smallest minimum is narrowed to about a second of time by golden-section search. If the separation only falls or only rises through the span, the end that is smaller is returned and atEdge says so. With by: "sky" the separation is the angle in the sky of the observer and a minimum may be an occultation, the angle falling through 0; with by: "space" it is the distance between the centres.

The result carries uncertaintyArcseconds (or uncertaintyKm) for the separation, from the accuracy guide's limits, and uncertaintySeconds for the moment: that error over how fast the pair moves past each other.

import { closestApproach } from "@johnmorrisdotca/wakusei-planets/nearest";

function closestApproach(a: BodyId, b: BodyId, options: ApproachOptions): Approach

import { closestApproach } from "@johnmorrisdotca/wakusei-planets/nearest";

const great = closestApproach("jupiter", "saturn", { from: Date.UTC(2020, 11, 1), to: Date.UTC(2021, 0, 1) });
console.log(great.time.toISOString(), great.angle?.toFixed(3), "degrees");

2020-12-21T18:25:35.939Z 0.102 degrees