Time: 16:00 h
Author: Robert Brakenridge
Planetary habitability may be affected by exposure to γ radiation from supernovae (SNe). SNe remnants offer a nearly-complete accounting for the past 40,000 years and including approximate SN distances and ages. Terrestrial changes in tree ring and other records of the cosmogenic isotope 14C are here compared to SN-predicted changes. There were 18 SNe ≤ 1.5 kpc, and brief 14C anomalies are reported for eight of the closest. Abrupt-increase anomalies in 14C production have been attributed to cosmic rays from exceptionally large solar flares. However, the proximity and ages of these SNe, the probable size and duration of their γ emissions, the predicted effects on 14C, and the agreement with 14C records together support SNe causation.