Solar system exposure to supernova gamma radiation

摘要

Planetary habitability may be affected by exposure to gamma radiation from supernovae (SNe). Records of Earth history during the late Quaternary Period (40 000 years to present) allow testing for specific SN gamma radiation effects. SNe include Type Ia white dwarf explosions, Type Ib, c and II core collapses, and many gamma burst objects. Surveys of galactic SNe remnants offer a nearly complete accounting for this time and including SN distances and ages. Terrestrial changes in records of the cosmogenic isotope C-14 are here compared to SN-predicted changes. SN gamma emission occurs mainly within 3 years; average per-event total emissions of 4 x 10(49) erg are used for comparison of close events There are 18 SNe <= 1.5 kpc, and brief C-14 anomalies are reported for eight of the closest. Four are notable (BP is year before 1950 CE): the older Vela SNR and an abrupt 30 parts per thousand del C-14 rise at 12 740 BP; S165 and a 20 parts per thousand rise at 7431 BP; Vela Jr. and a 14 parts per thousand rise at 2765 BP; and HB9 and a 9 parts per thousand rise at 5372 BP. Rapid-increase anomalies in C-14 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 gamma emissions, the predicted effects on C-14, and the agreement with C-14 records together support SNe causation. Also, the supposed solar-caused C-14 anomalies at CE 774 and 993 may instead have been caused by the SNe associated with the G190.9-2.2 and G347.3-00.5 remnants. Both are of appropriate age and distance.