On the evening of December 7, 2022, the Moon will cross in front of Mars in a rare lunar occultation. Your location on Earth will determine what you'll see and what time it happens.
Let's start with a map of North America showing where the occultation is visible, inside the shaded area.
That’s most of the US, excluding most of the east coast and southeast. You’ll notice that the edge of visibility comes awfully close to Nashville. Let’s zoom in:
The southern edge of visibility is really close to Nashville! If you’re downtown, just outside of the occultation’s path, you’ll see the Moon and Mars just barely kiss. Southeast of the line, the Moon and Mars will appear very close to each other, but Mars won’t get hidden.
If you’re in the light-shaded area, (for example, Ashland city or White House) Mars will be partially but not completely blocked by the Moon.
Observers further to the northwest will see the Moon completely block Mars. The further northwest, the longer the occultation will last.
But don’t worry about traveling far northwest to get a longer occultation! While Mars is blocked, there’s not much to see until it comes back! If you want to watch Mars come back out of hiding, you won’t have to wait very long if you’re in, for instance, Clarksville.
The timing of this occultation is notable: December 7 also happens to be the date of the Full Moon, and December 8 marks the opposition of Mars – the date when Earth passes by Mars in its orbit. With Mars and Earth relatively close to each other, Mars is bright in the sky and bigger than usual in telescopes – exactly what you want to make an occultation even better.
What do you need to see the occultation?
A small backyard telescope will be best. It can magnify your view enough to see the round face of Mars gradually get hidden, and then revealed, by the Moon.
You can also view the occultation without a telescope – you’ll just see Mars gradually fade as it gets covered by the Moon. However, the bright Full Moon may make it hard to see Mars with the unaided eye.
What time will it happen? How long will it take?
That all depends on your location. Just northwest of Nashville, it will take place a few minutes before 9:30 pm. Go out by 9:15 or earlier to be prepared! Have a good view of the sky to the east.
The time it takes for the edge of the Moon to completely cover up Mars also varies based on location. Observers just northwest of the line are in an ideal spot – Mars will appear to slip behind the Moon at a steep angle and will take a few minutes to be completely covered up. Nearer the centerline of visibility (for instance, San Francisco on the map above), it will take just seconds for Mars to disappear. Wherever you are, be prepared if you’re planning to share a telescope with a friend or two!
To make the best prediction on when the occultation will take place near you, download and get familiar with the free desktop planetarium software called Stellarium. Enter your exact latitude, longitude and altitude, set the date and time, and watch the occultation ahead of time. Or head outside a little early and keep a close eye on the Moon and Mars!
While you’re waiting, check out red stars Aldebaran in Taurus the Bull, and Betelgeuse in Orion the Hunter, both not far away in the sky from the Moon and Mars. Jupiter will also be high in the southwest sky.