CUTTING EDGE

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- Prof Lewis Dartnell

Fireball over Jupiter outshines the Sun

The bright flash was caused by an impact the size of the Tunguska event

The spectacular collision of the comet Shoemaker-Levy 9 into Jupiter in 1994 was watched closely by observatories and space probes, and made headlines around the world. Since 2010, six impact flashes on Jupiter have been serendipitously observed, including by amateur astronomers. A simple brightness measurement allows for an estimate of the energy of such impacts, but far more accurate calculations can be made if they are recorded at several different wavelengths.

Ko Arimatsu, at the Astronomical Observatory, Kyoto University, and his colleagues have been using the Planetary ObservatioN Camera for Optical Transient Surveys (PONCOTS), dedicated to monitoring flashes on Jupiter. The system is made up of a 28cm Schmidt-Cassegrain telescope on a rooftop at the university, equipped with two CMOS cameras. This setup allows the astronomers to observe flashes on Jupiter at three different wavelengths simultaneously: the V visible band in the yellow and two near-infrared bands.

On 15 October 2021, Arimatsu and his team observed a particularly bright impact flash on Jupiter,  occurring within the north tropical zone. The peak apparent brightness of the flash in the visible band was mag. 4.7, equivalent to an absolute magnitude of -29.0: roughly 300 times brighter than the Sun at Jupiter. And because their PONCOTS system can observe with a high frame rate across three wavelengths simultaneously, they were able to record this impact flash with unprecedented detail.

How big was the bang?