It wasn't a UFO. It was a Super Galaxy, an aircraft so big it can carry the equivalent of 70 Ford F-150 pickups.

Arp 184 or NGC 1961, a skewed or "peculiar" spiral galaxy, is still stunning in this image from the Hubble Space Telescope.

In an Adelaide school chapel half a century later, it's been remembered as both a prelude to unimaginable tragedy and a ...