Enjoying EarthSky? Subscribe.

270,139 subscribers and counting ...

Catch Mercury in the morning sky

These next few weeks will present a fine time for spotting Mercury, the innermost planet of the solar system, in the morning sky. You can easily planet-hop to Mercury by drawing an imaginary line from the red planet Mars through the king planet Jupiter to Mercury’s place near the horizon. No matter where you live worldwide, find a level and unobstructed horizon in the direction of sunrise. That’s because Mercury will sit quite low in the southeast sky, and close to the sunrise point on the horizon, as the predawn darkness is giving way to morning dawn.

Although this morning apparition of Mercury favors the Northern Hemisphere, it can still be viewed from the Southern Hemisphere. Mercury comes up sooner before sunrise at more northerly latitudes, yet closer to sunrise at more southerly latitudes. At mid-northern latitudes, Mercury rises about one and one-half hours before the sun; but at temperate latitudes in the Southern Hemisphere, Mercury only rises about one hour before the sun. Click here for recommended almanacs that’ll tell you Mercury’s rising time into your sky.

We recommend that you get up some 90 minutes or more before sunrise to see the morning spectacle. Depending on where you reside on the globe, Mercury may (or may not) have climbed above the horizon at this time. But Jupiter and Mars will be up well before dawn’s first light, and they’ll point out where Mercury will be rising into your sky.

Before dawn, look for the star Zubenelgenubi to shine right by Jupiter on the sky’s dome. Then use binoculars to see that Zubenelgenubi is actually as double star.

If you’re up before dawn, aim your binoculars at Jupiter to see the nearby star Zubenelgenubi, the alpha star in the constellation Libra the Scales. Jupiter and Zubenelgenubi will easily fit inside the same binocular field of view. Closely view Zubenelgenubi through your binoculars and you might even see that Zubenelgenubi is a double star.

Look first for Jupiter, the brightest starlike object to light up the morning sky. And then seek for moderately-bright Mars a short hop above Jupiter. Although Jupiter shines a good 20 times more brilliantly than Mars does, Mars is quite easy to see in the predawn sky. By the time that Mercury rises into the sky, Mars may (or may not) still be visible. But simply remember where on the horizon Mars and Jupiter were pointing. Do you have binoculars? They can help you to see Mercury when it first rises into the sky and still sits close to the murk of the horizon.

The good news is that Mercury will be climbing away from the glare of sunrise and brightening in our sky for the rest of this month. So if you miss seeing Mercury before sunrise on December 23, try planet-hopping to Mercury via the planets Mars and Jupiter each morning for the next few weeks.

Bruce McClure