Driftless Dark Skies: Moon Occults Mars

Mars will be glowing like an ember all night long in the December sky as we end 2022. It rises in the northeast at sunset, passes high across the southern sky, and sets in the northwest at sunrise. The Red Planet will be brighter than any star and almost as bright as Jupiter halfway across the sky to its right.

Mars and Earth are at their closest on November 30 (8:18pm CST) with “only” 50 million miles separating the two worlds. That’s still over 200 times the distance between Earth and Moon, and it will take 4 ½ minutes for the sunlight reflected by Mars to reach us as Marslight. Mars has not been this close since Oct 2020 and won’t be this close again until June 2033.

As December begins, Mars will be above the familiar constellation of Orion the Hunter. The red giant star Betelgeuse, the left shoulder of Orion, will be about two outstretched fists (20 degrees) below Mars. The orange giant star Aldebaran, the horn of Taurus the Bull, will be about one outstretched fist (10 degrees) to the right of Mars. Mars, Betelgeuse, and Aldebaran will make a very striking red-orange triangle that slowly changes shape during the month as Mars wanders among the fixed stars. As we wend through December, Mars moves away from Betelgeuse and towards Aldebaran. By December 31, Mars will be about one outstretched fist above Aldebaran and about an equal distance to the left of the Pleiades star cluster. If you have binoculars, get them out to better enjoy the reds and oranges of Mars, Aldebaran, and Betelgeuse contrasted with the bluish whites of the Pleiades.

We are in for a special treat the evening of December 7 when Mars Opposition occurs. Sun, Earth, and Mars are all in a line with our world orbiting between our star and our neighboring planet. These syzygies occur about every 26 months. The event this time is made even more special because there is a Full Moon that night with Earth passing between Sun and Moon as well as between Sun and Mars and all four will be in alignment for a time. It will not happen again until the evening of January 13, 2025.

On the evening of December 7, the Full Cold/Oak/Long Night Moon rises in the northeast around 4pm, about half an hour before sunset. As the Moon gets higher in the darkening sky, Mars will become visible left and a little below the Moon just about a finger’s width apart. Glare from the Moon may make it challenging to spot Mars, so binoculars will help. Keep watching as the Moon’s orbit brings it close to Mars. Then it happens. At 9:05pm CST, the Moon passes in front of Mars and begins to cover it up in an event known as an occultation. It will take almost a minute for Mars to fade from view. Mars is twice the diameter of the Moon, but its greater distance makes it appear 100 times smaller–still wide enough to not suddenly blink off. For the next hour, Mars is occulted as the Moon passes in front of it. Watch at 10:06pm as Mars slowly emerges from the right side of the Moon, and we get to be part of a rare Solar System event.

Winter Solstice is at 3:48pm CST on December 21. Wishing you well as we pass from one season to the next!

John Heasley is an astronomy educator and stargazer who enjoys connecting people with the cosmos. He volunteers with NASA/JPL as a Solar System Ambassador and the International Astronomical Union as a Dark Sky Ambassador. For more information about stargazing in southwest WI, like Driftless Stargazing LLC on Facebook and find out whenever there’s something awesome happening in the skies. Driftless Dark Skies appears monthly in the Voice of the River Valley.