His figures were roughly a centimetre tall, most made with two deliberate strokes of the brush, and allowed to fade away as his paint ran out, like the trailing tail of a comet.

ECONOMIST: Roman Opalka

"When they come close to the Sun, this ice melts - solar wind blows this material out into space, so you get a tail of matter coming off the comet, " explains O'Brien.

BBC: Star of Bethlehem: The astronomical explanations