Nemesis Reconsidered

TL;DR

This study investigates the Nemesis hypothesis by analyzing fossil biodiversity data, confirming a 27-million-year extinction periodicity but finding its regularity inconsistent with the predicted orbital perturbations, thus challenging the hypothesis.

Contribution

The paper provides a detailed analysis of extinction periodicity, using improved datasets to evaluate the Nemesis hypothesis and its plausibility based on timing regularity.

Findings

Identified a 27 My extinction periodicity in fossil data.

Confirmed the periodicity's association with extinction events at 99% confidence.

Found the regularity of the periodicity inconsistent with orbital perturbation predictions.

Abstract

The hypothesis of a companion object (Nemesis) orbiting the Sun was motivated by the claim of a terrestrial extinction periodicity, thought to be mediated by comet showers. The orbit of a distant companion to the Sun is expected to be perturbed by the Galactic tidal field and encounters with passing stars, which will induce variation in the period. We examine the evidence for the previously proposed periodicity, using two modern, greatly improved paleontological datasets of fossil biodiversity. We find that there is a narrow peak at 27 My in the cross-spectrum of extinction intensity time series between these independent datasets. This periodicity extends over a time period nearly twice that for which it was originally noted. An excess of extinction events are associated with this periodicity at 99% confidence. In this sense we confirm the originally noted feature in the time series for extinction. However, we find that it displays extremely regular timing for about 0.5 Gy. The regularity of the timing compared with earlier calculations of orbital perturbation would seem to exclude the Nemesis hypothesis as a causal factor.