Happen to have clear skies tomorrow morning and live in the western part of North America? Then you may have a chance to spy a unique event, as the waning crescent Moon occults (passes in front of) the planet Mars.
This is the ultimate cosmic photobomb, as our Moon slides in front of Mars in the twilight dawn sky. The bright limb of the Moon is always leading when the Moon is waning, meaning that Mars will disappear behind the illuminated crescent Moon, and reappear along the dark limb.
The Moon is a 24 percent illuminated crescent during the event, and Mars shines at +1.2 magnitude and presents a disk 5" across. Unlike a stellar occultation where a star abruptly winks out, planetary occultations are slow stately affairs.
Tuesday morning, it will take the Moon about 15 seconds to fully cover Mars, and a similar amount of time for it to reappear.
Of course, the two only look close to each other in the sky on Tuesday morning, as they lie along the same line of sight as seen from our Earthly vantage point.
The Moon is just shy of a quarter of a million miles away or just over one light-second distant, while Mars is 670 times farther, at 167 million miles or 15 light-minutes away.
This lunar occultation transpires in the dawn hours of Tuesday 18 February for North America.
Observers in the United States, central Canada and northern Mexico west of a line from the Great Lakes region to the Texas coast of the Gulf of Mexico will see the occultation under dark skies.
A sliver of land running from New Orleans to Chicago will see a hybrid event, with ingress occurring before sunrise and egress occurring after, while the US East Coast and the Canadian Maritimes will see the pair close at dawn, but the actual occultation occurring after sunrise.
As of writing this, weather prospects look to favor the western US. Keep in mind, you don't need a crystal clear sky to view the occultation: just a good clear view of Mars and the Moon.
Here's a look at local circumstances for the event for selected cities around the region:
You can follow the event either with the naked eye, binoculars or a telescope. Occultations are also fine events to capture on video, as you can see the action unfold in real-time. If you're observing east of the line, do not despair; you still have a shot at seeing +1st magnitude Mars near the daytime Moon.
Speaking of which, be sure to watch for an optical illusion known as the 'Coleridge Effect' at egress. This is a phenomenon where the nearby star or planet seems to hang Proctor and Gamble-style between the horns of the crescent Moon, in seeming defiance of physics.
The name comes from Samuel Coleridge's long poem Rime of the Ancient Mariner and the line "one bright star, almost atween the tips (of the) horn'd Moon."
Also keep an eye out for Jupiter, Saturn and the 'Anti-Mars' the bright star Antares, also in the same celestial dawn scene.
Mars is a prime target of interest in 2020, as it nears another fine opposition on 13 October 2020.
This also means this summer is Mars mission launch season, as four missions may make the journey to the Red Planet, including NASA's Mars 2020 rover, ESA's Exomars rover Rosalind Franklin, China's first Mars lander and orbiter, and the United Arab Emirates' Mars Hope orbiter.
The Moon actually occults Mars five times in 2020… but the 18 February event is the only favourable event for North America.
Here in Norfolk, we have to wait until the night of 13 and 14 January 2025 to see the Moon occult Mars… just a day prior to opposition. And stick around until April 26th, 2488 AD and head to Antarctica or southern New Zealand, and you can see the Moon occult Mars… during a total lunar eclipse
And here's a wacky one we just might live to see: a triple emoticon grouping of Mars, Mercury and the Moon on February 13th 2056.
Set your alarms tomorrow morning, and don't miss the 'Great North American lunar occultation of Mars'.
Read about occultations, eclipses and more in our book, The Universe Today Ultimate Guide to observing the Cosmos.