Studying stellar flares and cosmic explosions - using tree rings!

Project level: Honours

Radiocarbon dating is used by archaeologists to determine the ages of wooden artefacts and remains of living things, by measuring how much carbon-13 has decayed to carbon-12 since the material last took in fresh carbon from the air. The amount of carbon-13 in the atmosphere has slowly varied over time due to solar activity and volcanic eruptions, so to calibrate their radiocarbon dates, archaeologists use precise measurements of tree rings of known age. With alternating patterns of slow and fast growth, tree rings form a barcode pattern that can be matched to libraries stretching back millennia, giving us precise radiocarbon references for almost any year since the last Ice Age.

In 2012, a remarkable discovery was made by Fusa Miyake: in 774 AD, there was a huge spike in radiocarbon all over the world, that decayed over the course of a year or two, and may have been associated with powerful aurorae noted by mediaeval monks. It was almost certainly astrophysical in origin. Now several 'Miyake events' have been discovered, and astronomers wonder: was this a powerful solar flare? A supernova? Or the result of a 'magnetar burst', the powerful blast of a magnetised neutron star rearranging itself.

New radiocarbon data in the IntCal20 record are ripe for analysis, by statistically digging into the vast new dataset to find new Miyake events hiding in the noise. We can then determine the true rate of their occurrence, their amplitude and timing, and help narrow down the astrophysical origin of this event. This is an ideal Honours project for a student with strong Python skills and an interest in statistics and interdisciplinary studies.

For more reading, see Traces of sun storms locked in tree rings could confirm ancient historical dates