History books may tell you that in the eighth century, the Moors
invaded Spain and Mayan civilization was on the decline, but
they don't say anything about the Earth being irradiated. That
event is not documented, but astronomers say a collision in
space at that time could have resulted in the high levels of
carbon-14 and beryllium-10 found in trees from the eighth
century. Astronomers Valeri Hambaryan and Ralph Neuhauser, based
at the Astrophysics Institute of the University of Jena in
Germany, published results in the journal Monthly Notices of the
Royal Astronomical Society that suggest that two "compact
stellar remnants" -- which could be neutron stars, black holes
or white dwarfs -- collided and merged, resulting in a short-
duration gamma-ray burst that hit Earth. The astronomers started
looking into this possibility on the heels of results announced
in 2012. Scientist Fusa Miyake suggested that high levels of
carbon-14 and beryllium-10 found in tree rings from 775 A.D.
could be evidence that Earth was h