Estimating Dimensions of the Nucleus of Great September Comet of 1882 from Motions of Its Fragments

TL;DR

This study estimates the nucleus size of the Great September Comet of 1882 by analyzing fragment motions and tidal breakup, revealing a nucleus about 60 km in size and implications for future sungrazers.

Contribution

It introduces a method to estimate comet nucleus size from fragment velocities and applies it to the 1882 comet, linking fragmentation dynamics to future sungrazers.

Findings

Nucleus size estimated at about 60 km.

Fragment velocities reflect tidal forces at breakup.

Potential future bright sungrazer from 12th-century fragmentation.

Abstract

Data on perihelion fragmentation of the Great September Comet of 1882 (C/1882 R1), a prominent member of the Kreutz sungrazer system, are employed to estimate the size of the nucleus along the radius vector at the time of splitting. The prolate-spheroidal nucleus is assumed to fragment tidally at perihelion along planes normal to this direction. The relative velocities, derived by Sekanina & Chodas (2007) from revised positional-separation data on six fragments collected originally by Kreutz (1888) are interpreted as measures of the Sun's differential gravitational acceleration on the centers of mass of adjacent fragments at the time of breakup and therefore a function of heliocentric distance. Their total of 7.8 m/s is equivalent to nearly 38 km in the sum of distances of the centers of mass along the radius vector and to the nuclear size of about 60 km. The observed sheath of diffuse material, the remains of the crumbling part of the nucleus that ended up enveloping the train of the six fragments, included a population of less massive fragments. They are expected to feed, over centuries in a distant future, an influx of dwarf sungrazers reminiscent of the current stream of SOHO Kreutz comets. It is speculated that the parent comet of C/1882 R1 experienced similar fragmentation in the early 12th century and one of its major fragments -- a bright sungrazer -- may return in the mid-21st century.