December is “Star of Bethlehem” season to those of us who give public talks on astronomy. This year is special, however, because one of the more popular explanations for the “star” – a close conjunction of the bright planets Jupiter and Saturn – is actually playing out in the heavens overhead, visible to anyone with a clear sky. Look soon after sunset for Jupiter, the bright “star” to the west; nearby is a somewhat fainter yellowish spot of light, which is Saturn. All month, Jupiter will be creeping closer to Saturn. On 21 December they’ll be so close together that your naked eye won’t be able to tell them apart.

So is this really what the Star of Bethlehem was? Well, nobody’s expecting another Saviour to be born anytime soon. (But then, that’s what they thought 2,000 years ago.) More to the point, you can actually see from how the two objects look to your own eyes that adding Saturn’s light to Jupiter’s probably won’t make any visible difference to Jupiter’s brightness. What sounds dramatic on paper is likely to be just a nice curiosity to the casual observer.