Moon occults Mars tonight: How to watch

The moon occults Mars on December 7-8

Here’s hoping you have clear skies on the night of December 7-8, 2022, because there’s much to see! First, the full moon is up all night, near bright red Mars.

You say you’ve looked that night, and can’t see Mars near the moon? That might be because you’re looking when Mars is behind the moon. In fact, the moon will pass in front of the red planet, as seen from much of North America and Europe, on the night of December 7-8. Astronomers call this event an occultation. The moon is said to occult Mars. It eclipses it, or covers it.

This fascinating and unusual event appears to North American skywatchers who are northwest of a diagonal line drawn from Augusta, Maine, through Columbus, Ohio, through Little Rock, Arkansas, and San Antonio, Texas, extending into Mexico. The map below will let you know if your part of the world gets to view the occultation.

Watch the occultation online via Virtual Telescope!

Who will see the moon occults Mars? And when?

If you’re in the viewing area indicated on the chart above, you’ll also need a precise time for your location. The event will happen on the evening of December 7 for most of us in North America. Check out In-the-Sky.org to find the precise time Mars will disappear and reappear from wherever you are.

For those who live outside the viewing area, as in the southeastern United States, you’ll see the moon and Mars skim right past each other. Some places will even get to see Mars play peekaboo along the cratered and mountainous limb of the moon.

Here are some livestreams for the Mars occultation:

What will you see?

A full moon is bright. And it’s totally illuminated as seen from Earth. People who observe occultations typically try to catch both the disappearance and reappearance of the star or planet, as it’s blotted from view. But this sort of observation is much easier if you watching a darkened edge of the moon. And we don’t have a darkened edge available to us at full moon. By definition, a full moon is entirely illuminated, as seen from Earth.

Plus most regular occultation observers use telescopes (such as those observers hosting the livestreams listed above).

So what will you see of the December 7-8 occultation of Mars, if you try to watch in the sky? The answer depends on how hard you try, what tools you use, where you are on Earth – as always, on the quality of your night sky – and on your skill at observing events like this.

Mars is at its brightest now. So, with the eye alone, we should all be able to spot Mars in the moon’s glare.

But you’ll see more if you use binoculars. And even more with a telescope (although the glare of the full moon will be intense through your ‘scope’s eyepiece).

And, wow, what a great photo opportunity!

It’ll be a tricky observation. But many will be watching. As veteran skywatcher Bob King (aka AstroBob of the Duluth News Tribune) wrote at SkyandTelescope.com:

I’m really curious if we’ll continue to see Mars with the unaided eye right up to the moon’s edge. I suspect we will. Also, at what point will the planet disappear from view as it dips behind the moon? Keep those binoculars handy! Telescopic observers will get fabulous views, especially those living within the southern graze zone, where the moon will partially occult the planet.

Thanks, AstroBob!

Why is it happening?

Earth goes between the sun and Mars about every two years. That’ll happen around 6 UTC (12 a.m. CST) on December 8. This is Mars’ opposition, an event we astronomers wait for, and enjoy.

A full moon happens every month. And this month’s full moon comes just a couple of hours before Mars’ time of opposition, at 04:08 UTC on December 8, 2022 (10:08 p.m. CST on December 7).

A full moon appears full to us because it’s opposite the sun from Earth. And Mars – or any outer planet – is opposite the sun from Earth at opposition. So it’s no surprise that this month’s full moon is somewhere near Mars. Planets are always near the full moon sometime around their time of their oppositions.

What’s so special in 2022 is that these events – full moon and Mars’ opposition – happen so near each other in time. Around 4 to 6 UTC on December 8, the sun, Earth, moon and Mars will be nearly in a line.

And, what’s more, the full moon won’t just pass near Mars in the sky. Its path across the sky (which varies in an 18-year cycle) is such in 2022 that it’ll pass directly in front of Mars.

Very cool!

Read: December on December 7-8 full moon mimics the June sun

Read: Mars at opposition on December 7-8

Bottom line: On the night of December 7-8, 2022, the full moon will occult, or cover over, Mars. Just hours later, Earth will pass between Mars and the sun. Details here.