Now – mid-December 2018 – it’s time to get outside in the early morning and try to spot our sun’s innermost planet, Mercury. Look east, the sunrise direction. You can’t miss super-bright Venus. Mercury is below it, near the sunrise point. If you look extra hard with the unaided eye or binoculars, you might spot bright Jupiter near the horizon, too, on a line with Venus and Mercury.
Mercury shines more brightly than a 1st-magnitude star now; in other words, it’s as bright as the brightest stars in our sky (but not nearly as brilliant as Venus). Bring along binoculars, if you have them, though. With daylight coming up fast, you could easily lose Mercury in the morning twilight.
You’ll need an unobstructed horizon in the direction of sunrise. Depending on where you live worldwide, Mercury might – or might not – be above the horizon some 90 minutes before sunrise. If you don’t see it at first below dazzling Venus, wait a bit. As Earth spins under the sky, as dawn’s light is filling the sky, Mercury will be ascending higher in the east.
Jupiter is climbing upward now, too – day by day – toward Mercury, in the December 2018 morning sky. In mid-December, the bright morning twilight might render Jupiter invisible or nearly so. Fortunately, Jupiter should become easier to see by the time this brilliant world pairs up with Mercury on December 21. See the chart below.
This morning apparition of Mercury favors the Northern Hemisphere. The farther north you live, the more time that Mercury rises before sunrise; the farther south you live, the closer that Mercury rises to sunrise. Assuming a level eastern horizon, we give the approximate amount of time that Mercury rises before the sun at 45 degrees North latitude, the equator (0 degrees latitude) and 45 degrees south latitude:
45 degrees north latitude: Mercury rises approximately 100 minutes before sunrise
Equator (0 degrees latitude): Mercury rises approximately 80 minutes before sunrise
45 degrees south latitude: Mercury rises approximately 60 minutes before sunrise
Click here for a recommended almanac that’ll give you Mercury’s precise rising time in your sky.
Although the sky charts above and below are designed for mid-northern latitudes, you can easily apply them to any part of the world with a few simple considerations:
At latitudes significantly north of the equator: Mercury is found to Venus’ lower left
At latitudes at or near the equator: Mercury is found pretty much directly below Venus
At latitudes significantly south of the equator: Mercury is found to Venus’ lower right
Bottom line: In mid-December 2018, look for Mercury – and possibly Jupiter – below Venus in the east at dawn.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.