Nemesis reconsidered

• Published in: Monthly notices of the Royal Astronomical Society. Letters 2010-09, Vol.407 (1), p.L99-L102
• Main Authors: Melott, Adrian L., Bambach, Richard K.
• Format: Article
• Language: English
• Subjects: astrobiology; binaries: general; Oort Cloud; planets and satellites: general
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1111/j.1745-3933.2010.00913.x

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 data sets of fossil biodiversity. We find that there is a narrow peak at 27 Myr in the cross-spectrum of extinction intensity time series between these independent data sets. This periodicity extends over a time period nearly twice that for which it was originally noted. An excess of extinction events is associated with this periodicity at 99 per cent 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 Gyr. The regularity of the timing compared with earlier calculations of orbital perturbation would seem to exclude the Nemesis hypothesis as a causal factor.