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Are periodic mass extinctions driven by a distant solar companion?


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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Whitmire, D., Jackson, A. Are periodic mass extinctions driven by a distant solar companion?. Nature 308, 713–715 (1984).

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