At about 05:00 local time on Tuesday, observers looking east from London — and elsewhere with a similar horizon view — will be able to spot a slim waning crescent moon drawing close to the bright planet Jupiter.
The lunar crescent will be readily visible with roughly 10% of its visible surface illuminated, while Jupiter will appear as a brilliant beacon nearby. Astronomers describe the event as a conjunction: later that day the moon will pass less than one degree north of the gas giant.
For context, the moon’s apparent diameter in the sky is about half a degree, making the close approach easily appreciable to the naked eye under clear conditions. Mars will also be in the scene, located a little further from the moon–Jupiter pairing.
The moon’s motion is rapid enough that by the following morning it will have shifted to the other side of Jupiter. Early-morning sky charts and local viewing conditions can help amateur observers identify the precise positions.