Step outside during dusk on Wednesday, Dec. 7, and look low in the east-northeastern sky. There you’ll see the rising full moon, and nearby you’ll notice a glowing orange “star.”
But this isn’t a star at all; it’s the Red Planet Mars.
Mars now appears against the stars of Taurus, the bull, which of course lie trillions of miles farther and appear only roughly along the same line of sight. The planet reaches its closest to Earth during this orbital cycle on that night, when it lies about 51 million miles away.
If you own a small telescope or can visit your local planetarium or amateur astronomy club, you’ll get quite a close-up view of Mars at this time. With even the lowest magnification you’ll easily see its orange disk, but a larger telescope with higher magnifications will show some dark features on the planet’s surface.
Mars will be in a great position for viewing all month long.
On the evening of Dec. 7, however, don’t just glimpse at Mars and quit because, if you’re patient, you can watch the moon play a game of hide-and-seek with the Red Planet.
What you will see (and when) depends on where you live; some sky watchers will see Mars on the left side of the moon, while others will see it on the right. And some may not see it at all.
Why? Because on that evening the moon (only 246,000 miles away) will drift in front of Mars and create what astronomers call an “occultation.” When and where you observe will determine whether you’ll see Mars or if it will be hidden behind the solid disk of the moon.
The occultation will be visible to sky watchers throughout most of North America and northern Europe, but those in the far eastern and southeastern United States and Mexico will miss it.
Stargazers in Santa Barbara County, for example, will see the planet’s vanishing act (its “ingress”) behind the moon’s eastern limb around 6:30 p.m. PST. From the Kansas City area, the ingress will occur at around 8:56 p.m. CST; from Pittsburgh, watch for the planet’s disappearance around 10:34 p.m. EST.
Many East Coast locations, like New York City, for example, won’t see the occultation at all because Mars will pass just below the moon and will not be blocked by its disk.
It’s not only the planetary disappearing act that will be of interest. Not long after the planet vanishes, it will reappear on the opposite side of the moon.
Spotting this, however, will be more challenging since it’s tough knowing exactly where Mars will emerge from behind the moon’s western limb. From Los Angeles, this “egress” will occur at around 7:30 p.m. PST. From Kansas City watch for it around 9:52 p.m. CST, and in the Pittsburgh area, it happens around 10:58 p.m. EST.
Because the exact times of this occultation depend on your location, you should get more accurate times for your town by calling your local planetarium, observatory or amateur astronomy club. And always plan to begin your watch at least 15 minutes early so you can watch the moon approach the planet in the sky.
— Dennis Mammana is an astronomy writer, author, lecturer and photographer working from under the clear dark skies of the Anza-Borrego Desert in the San Diego County backcountry. Contact him at firstname.lastname@example.org and connect with him on Facebook: @dennismammana. Click here to read previous columns. The opinions expressed are his own.