When you buy through links on our articles, Future and its syndication partners may earn a commission.Eager skywatchers can see Mercury in the December night sky. . | Credit: Chris Vaughan/Starry NightIf there ever was a planet that has gotten a bad rap for its inability to be readily observed it would have to be Mercury, known in some circles as the “elusive planet.”Mercury is called an “inferior planet” because its orbit is nearer to the sun than the Earth’s. Therefore, it always appears from our vantage point to be in the same general direction as the sun. So near to the sun that it is often difficult to see with the unaided eye. In fact, Copernicus complained that he had never been able to enjoy a view of it, and this was doubtless because he lived at Frombork in northern Poland, near the Vistula River, where the sky near the horizon is often hazy owing to local mists and fog.AdvertisementAdvertisementNonetheless, during the first three weeks of December we will be presented with an excellent opportunity to view Mercury in the early morning dawn sky. If you’ve never sighted this rocky little world for yourself, you’ll never get a better opportunity than right now to see it. So set your alarm clock for around 5:30 a.m. and head outside to a location with a clear and unobstructed view of the east-southeast sky.Rise to prominenceOn Nov. 20, Mercury was at inferior conjunction with the sun, passing roughly between the sun and our Earth. Four days later on Nov. 24, Mercury passed just one degree north of brilliant Venus, but the pair were only 10 degrees from the sun and rising about 50 minutes before sunrise, shining at a magnitude of +2.4. Mercury was still impossible to see through the brightness of dawn.But only three days later on Thanksgiving Day (Nov. 27), Mercury was rising 75 minutes before the sun and increased by a factor of 3.6 times in brightness to magnitude +1.0. It was then fairly easy to locate, close to the east-southeast horizon about an hour before sunrise.Mercury’s visibility continued to improve rapidly and by Friday morning, Dec. 5 it will rise shortly before morning twilight begins — in a dark sky — and will have brightened markedly to magnitude -0.3. Now all you have to do is just look low above the east-southeast horizon from 40 to 80 minutes before sunrise for a bright yellowish-orange “star.”AdvertisementAdvertisementAn unusually favorable greatest elongation occurs on Sunday, Dec. 7, even though Mercury is only 21 degrees from the sun. At magnitude -0.4 (among the stars only Sirius and Canopus are brighter), it rises in a dark pre-twilight sky about one ho …
