Nature 308, 713 - 715 (19 April 1984); doi:10.1038/308713a0

Are periodic mass extinctions driven by a distant solar companion?

Daniel P. Whitmire^* & Albert A. Jackson IV^†

^*Department of Physics, University of Southwestern Louisiana, USL Box 44210, Lafayette, Louisiana 70504, USA
^†Computer Sciences Corporation, 1300 Bay Area Blvd, Houston, Texas 77058, USA

Raup and Sepkoski¹⁻³ have recently reported evidence for a 26-Myr cycle in biological mass extinctions which, if real, requires an astronomical explanation. Here we investigate a model in which this extinction cycle is associated with the orbital period of a solar companion star. The required semi-major axis is (a _*), semi-major axis) 8.8 10⁴ AU = 1.4 light yr. Its highly eccentric orbit (e _* 0.9) periodically brings the companion into the dense inner region (2 10⁴ AU) of the comet cloud where it perturbs the orbits of large numbers of comets, initiating an intense comet shower⁴ in the Solar System which results in several terrestrial impacts over a period of 10⁵−10⁶ yr. The companion probably has a mass in the black dwarf range of 2 10^-4 to 7 10^-2 M , depending on its eccentricity and the density distribution of comets in the inner cloud, and is potentially observable in the infrared.

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