The full Moon is always a sight worth looking at. This March, the full Worm Moon is a little more “super” than usual.
The full Moon is always a spectacular sight: the night sky’s brightest object by far.
On June 18, 2007, the planet Venus passed behind the thin crescent Moon as seen from many locations on Earth. Even when the Moon is close to its new phase, it outshines Venus by a factor of many hundreds; in its full phase close to perigee, it can rise up to ~2000 times the brightness of Venus, which it will achieve on the evening of March 9, 2020. (HASSAN AMMAR/AFP via Getty Images)
At 100% illumination, it’s ~2000 times brighter than the next brightest object, Venus.
When the Moon is close to its nearest point to Earth in orbit, perigee, at the same time that it’s fully (100%) illuminated by the Sun on its Earth-facing side, we achieve what’s known as a supermoon: the brightest and largest full Moons as seen from our planet. (REX BOGGS / FLICKR)
On Monday night, March 9, Earth will experience the full Worm Moon, the first of two consecutive supermoons.
The Moon’s orbit isn’t a perfect circle, but an ellipse. When perigee coincides (or nearly coincides) with fullness, we achieve a Supermoon. (BRIAN KOBERLEIN)
Just 13 hours later, the Moon will reach perigee: the closest point in its elliptical orbit to Earth.
Compared to an apogee (most distant) Moon, a perigee (closest) full Moon can be approximately 14% larger and 30% brighter. (TOMRUEN / WIKIMEDIA COMMONS)
The full Moon aligning with perigee is what makes this astronomical event a supermoon.
The cycle from new Moon to full Moon to new Moon again coincides with increases and decreases in apparent size as the Moon moves along its elliptical orbit. Because it moves faster at perigee and slower at apogee, but has a constant rate of rotation, we see slightly more than 50% of the Moon over the course of a lunar month: this is the phenomenon of lunar libration. When perigee and fullness coincide, we see a supermoon, but this changes over time with a 411 day period. (WIKIMEDIA COMMONS USER TOMRUEN)
Compared to an average full Moon, supermoons are 7% larger and 15% brighter.
As seen from the Americas, the full Worm Moon will be at its largest and brightest immediately after sunset in the eastern portion of the sky. (Tayfun Coskun/Anadolu Agency via Getty Images)
In the Americas, the Moon will appear brightest in the early part of the night, located near the eastern horizon.
Although the Moon will be at its fullest in the early hours of the night of March 9, 2020, for Europe and Africa, it will reach its brightness a few hours later as perigee approaches, where it will be either overhead or in the north or south portion of the sky, depending on your latitude. (Henning Kaiser/picture alliance via Getty Images)
In Europe and Africa, peak brightness occurs as perigee approaches a few hours after maximum fullness, closer to midnight.
In eastern Asia and Australia, the best time to view the full Worm Moon at its brightest will be in the pre-dawn hours of March 10, when the Moon is just a little bit past its full illumination of 100% but prior to reaching perigee and its closest distance to Earth. (Sergei MalgavkoTASS via Getty Images)
In Asia and Australia, the Moon achieves maximum brightness during March 10th’s pre-dawn hours, located in the western skies.
What makes a Supermoon so super? It’s the fact that the Moon’s difference between apogee (its farthest distance from Earth) and perigee (its closest approach to Earth) is so significant; it varies by about 14%. Because the Moon is roughly spherical, this corresponds to a difference of up to 30% in brightness between an apogee and perigee full Moon. (LOIC VENANCE/AFP/GETTY IMAGES/E. SIEGEL)
The next supermoon, on the night of April 7/8, will be 2020’s brightest, ~0.5% brighter than this year’s full Worm Moon.
The Moon takes a little over 27 days to orbit 360º around Earth, a little over 29 days to go from new Moon to new Moon again, but a total of 14 lunar cycles, or 411 days, to go from a full Perigee Moon to a full Perigee Moon again due to the motion of its elliptical orbit around the Sun. This pattern will continue indefinitely, leading to the largest and brightest full Moon of our lifetimes on November 25, 2034. (ORION 8 / WIKIMEDIA COMMONS)
Last year (2019), the Worm Moon was both a supermoon and the full moon closest to the equinox. This year (2020), the full Worm Moon is also a supermoon. Next year (2021), the phases of the Moon will have shifted out of alignment with perigee, and the full Worm Moon will not be a supermoon any longer. (Atilgan Ozdil/Anadolu Agency/Getty Images)
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
