A very surprising number of skywatchers, even experienced amateur astronomers, have never seen Mercury. But why?With a maximum magnitude of -1.9, it’s far brighter than the brightest star in the sky, so it should be really obvious to the naked eye. The problem is its proximity to the Sun.Mercury is the closest planet to the Sun, so close that it takes only 88 days to whip once around it, which means it never strays far from the Sun in the sky. Because of its tight orbit, we never see Mercury in a dark sky like we do with Venus and every other planet. We can only see Mercury low in the sky just before sunrise or just after sunset, when the sky isn’t properly dark. We only ever see Mercury low in the sky, too, so for many skywatchers it’s always hidden by trees, buildings or hills they have on their eastern or western skylines. For these reasons Mercury is often labelled ‘elusive’, but this month will be a great opportunity to see it.
At the end of December Mercury will be a morning object, visible low in the southeast before the Sun rises. It will have plenty of company in the morning twilight – fainter Mars will be directly beneath it, and much brighter Venus will be shining to its upper right. With a magnitude of +1.1, Mercury should be easily visible to the naked eye, rising an hour and a half before the Sun, but you might need a pair of binoculars to pick it out from the bright background sky if it’s a bit hazy or murky.