Jupiter and Saturn Say Goodbye, Mercury Beams a Bright 'Hello!'

Jupiter and Saturn are seen here on Jan. 8, 2021 in bright twilight about 50 minutes after sunset. They are currently 2° apart but appear more separated because I used a 200mm telephoto lens to magnify the scene so Saturn would show more clearly. Bob King

When was the last time you saw Jupiter and Saturn? Not since their great conjunction? You don't have much time left. The planet pair is quickly slipping into the twilight glare. As you can see from the photo I almost missed Saturn. Thank goodness for that gap in the trees! Although Jupiter was easy to spot despite its altitude of just 3° at the time I never found Saturn because — I hate to admit this — I forgot to bring binoculars. 

The same way Jupiter and Saturn were in conjunction on Dec. 21, 2020, each planet will take its turn in conjunction with the sun. Saturn goes first on Jan. 24, followed 5 days later by Jupiter. Since they'll be in the same line of sight as our friendly star, the planets will be invisible for several weeks until they reemerge in the southeastern sky at morning twilight in February. 

As Saturn and Jupiter depart, Mercury climbs into view starting tonight (Jan. 9). To see them, look very low in the southwestern sky starting 45 minutes after sunset with binoculars. Jupiter will only be about 4-5° high at that time with Saturn around 2°. One degree is equal to the width of the tip of your little finger held at arm's length. Stellarium

Only a few evenings remain to see them. As you can tell from the photo you'll need a clear view as far down to the southwestern horizon as possible. Although Jupiter's not difficult to see 50-60 minutes after sunset without optical aid, you'll need to start looking 40-45 minutes after sunset if you hope to catch a glimpse of Saturn. Binoculars are necessary to spot it. Find your sunset time here.

Carol Behan found all three planets from St. Stephen, New Brunswick on Jan. 10. Jupiter is at top, Mercury to the lower left and Saturn at lower right. "Jupiter was quite bright, Mercury dimmer and Saturn barely visible at all," wrote Behan. Carol Behan

As Saturn quickly departs the scene it's replaced by fresh-faced Mercury which sidles up alongside Saturn and then Jupiter before leaving the duo in the dust. Although Mercury is fainter than Jupiter it's more than a magnitude brighter than Saturn and will be easy to see in binoculars and even the naked eye as it gains altitude over the next week. 

Jupiter will be in conjunction with the sun early on Jan. 29, passing less than 1/2° to its south. Stellarium

Mercury will appear farthest from the sun (called greatest elongation) on Jan. 23 and best visible from about Jan. 13-30. Saturn will only be around for a few more nights, and Jupiter will disappear at mid-month, but before they do you might just get to see the three planets play musical chairs at dusk. 

By late January, Mars will become the sole naked-eye, evening planet. And it's still bright at magnitude 0.1, equal to the star Rigel diagonally opposite Betelgeuse in the foot of Orion. In an upcoming article we'll use Mars to point us to two small but distinctive fall-winter constellations.