Mars approaches a grazing lunar occultation on September 5, 2020. Image courtesy of Delberson Tiago de Souza at Astrobin under the Creative Commons License.
Set a reminder – and hope for clear sky – on the night of December 7-8 as a remarkable event takes place – a full December ‘Cold Moon’ passing in front of Mars just two hours before the planet reaches opposition. The event is visible through parts of western Europe, Canada, and the U.S. except for the eastern seaboard, the southeast, and Alaska. You can see the event without optics, with binoculars, or the telescope of your choice. It will be an astronomical event to remember.
As it reaches opposition, orange-hued Mars shines at a spectacular magnitude -1.9, brighter than any star, in the constellation Taurus. You can’t miss it. The planet lies within a finger-width or two of the full Moon before the occultation takes place. The event gets underway as the planet passes behind the eastern side of the Moon and appears about an hour later from behind the western limb as the Moon slowly makes its way eastward. Since the planet lies at opposition, its 17”-wide disk appears large enough to reveal surface detail if seeing conditions allow. With a telescope, crank up the magnification to see the planet disappear and reappear behind the lunar limb; from some locations, it may appear to pass behind lunar mountains or other high-relief lunar surface features.
When does this all happen? Since the Moon lies relatively close to Earth at a distance of about 30 times the Earth’s diameter, the precise timing of the event depends on the observer’s location. From my location, in Calgary, the occultation runs from 19:58 to 21:03 MST on the 7th. In Chicago, it runs from 21:08 to 22:06 CST, also on Dec. 7. And from London, the occultation occurs from 04:58 to 05:59 GMT on the morning of Dec. 8. You can find the precise timing of the event at this link.
And while the occultation passes quickly, you can continue to enjoy Mars in the coming weeks as it stays large and bright. Have more than one look, however – observing Mars well takes practice, and it is, like most important things, a perishable skill. Be patient and keep looking! The Cosmic Pursuits guide to observing Mars has lots of tips and ideas to help you enjoy this opposition. The next one doesn’t arrive until January 16, 2025!Share This: