Our night sky is getting lit up like a Christmas tree! Not only do we have all the bright stars and constellations of winter on the rise, but also three naked-eye planets: Venus, Saturn and Jupiter all visible as evening twilight ends. Shortly after 7 p.m., the planet Mars joins the party, rising above the eastern horizon with its distinct orange-red hue. It’s not nearly as bright as Jupiter and Venus, but the planet named after the Roman god of war is undoubtedly the brightest star-like object in the low eastern sky, and it’s only going to get brighter.
Mars and Earth are nearing their closest approach to each other in over two years. The astronomical term for this is opposition. This only happens every other year because while it only takes Earth a little over 365 days to make a complete orbit around the sun, it takes Mars 687 days. Mars and Earth are constantly trying to catch up with each other to align. Every 780 days, it accomplishes that, and we get up close and personal with the red planet. Earth and Mars will reach opposition Jan. 16 when they’ll be separated by less than 60 million miles. Another benefit of opposition is that Mars is available to see all night, rising at sunset and setting at sunrise. We’re just about at that point now.
Mars peeking out behind the moon (Mike Lynch)
Some oppositions are closer than others, however. That’s because the orbits of Mars and Earth are not exactly circular but elliptical or oval-shaped. Earth and Mars both have a maximum and minimum distance from the sun in their orbits. The maximum distance is called aphelion, and the minimum is called perihelion. If opposition occurs when Earth is at its aphelion and Mars is at perihelion, then the separation between the two planets is at its minimum, and Mars gets super big and bright in our sky. That doesn’t happen very often though. That was the case in 2003 when Earth and Mars were separated by only 34.6 million miles. It was the closest Earth and Mars had been to each other in 60,000 years.
Even though Mars isn’t going to get that close during the coming opposition, it’s close enough to backyard telescopes to get some good views of the red planet, but seeing a lot of detail is tricky. Mars is only half the diameter of Earth at 4,000 miles. Also, Mars will appear super fuzzy when it first rises, but it’ll be less fuzzy a little after 9 p.m. when it rises far enough above the blurring effects of Earth’s atmosphere close to the horizon.
You’ll need patience and persistence to observe Mars through any telescope. Viewing conditions can vary from night to night. Not only do you need clear skies, but you also need a reasonably still, non-turbulent atmosphere between you and Mars. Strong winds aloft can certainly murk up the viewing conditions. Don’t give up if you don’t see much detail on Mars. Try other nights when Earth’s atmosphere is a little more settled. It’s also a good idea to take long, continuous looks at Mars through your telescope. Quick glances usually don’t work because you must let your eye get used to the light levels coming into the eyepiece of your scope. You won’t see many surface features through most smaller telescopes, although you might see part of the planet’s northern polar cap. If your telescope gives you an inverted view, as most scopes do, you may see a whiteish tinge on the lower edge of the disk. If conditions are just right and especially if you have a larger scope, you may also see some dark splotches on Mars that are a part of its extensive system of valleys and mountain ranges.
Even if you can’t see many details on Mars through your scope, our current Mars invasion is still a lot of fun. If nothing else, it adds to the colors in our holiday December sky!
Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can contact him at mikewlynch@comcast.net.
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