Astrophysics with Radioactive Isotopes

Verifying footprints of solar cycles and supernovae in polar ice cores

Not scheduled

20m

Oral Presentation

Speaker

Yuko Motizuki (RIKEN)

Description

Polar ice cores can yield information about astronomical phenomena as well as
information about climate changes of the past. More than 40 years ago, Rood
and his colleagues suggested a possibility that such a polar ice core preserved
footprints of historical supernovae and solar cycles (Rood et al., Nature, 1979).
In the Rood’s work, the signatures of three historical supernovae were identified
as “spikes” found in the depth profile of nitrate ion concentrations. This was a
preliminary result, however, as the authors themselves mentioned in the
literature, and was followed by criticism based on analyses from several other
ice cores in traditional glaciology. The group finally withdrew their original
hypothesis in 1983 as contamination with analysis of their second ice core.
The report of detection of nuclear gamma-rays associated with 44Ti decays
from the young supernova remnant Vela Jr. (RX J0852.0-4622) shed light again
on the Rood’s work. This was because the third “unknown” spike out of four
identified spikes in the Rood’s paper was suggested to correspond to a footprint
of the supernova explosion of the newly detected Vela Jr. remnant (and, also
the withdrawal was not well known in our field of astronomy). I will review this
following line of work in glaciology, and why nitrate observations in ice cores are
difficult. I will also present our new result of chemical analyses in Dome Fuji ice
cores (Antarctica) which clearly show solar cycles and will discuss its meaning
as a touchstone to detect supernova candidate spikes as well as spike
structures we observed simultaneously. Perspectives to access the supernova
rate in the Milky Way will also be mentioned.