Did you see the full “blue supermoon” last night? If not, no fear—it will look almost as good tonight—but it was last night that it turned 100% lit as seen from Earth.
A rare celestial event as the only “blue supermoon” of the year graced the night sky, this spectacular event was captured by photographers across the world. Here are some of the best images:
The term “blue moon” is often used to refer to the second full moon occurring within a calendar month, something that can occur because the moon turns full every 29.5 days. However, there is another, more traditional definition—the third of four full moons to occur within one astronomical season.
The current season—summer in the northern hemisphere—began with the solstice on June 20 and will end with the equinox on Sept. 22. During that time, we have had June 21’s “Strawberry Moon” and July 21’s “Buck Moon.” Last night’s “blue supermoon” will be followed by Sept. 17’s “Harvest Moon” (incidentally, also a supermoon).
This month’s full moon was also the first “supermoon” of the year. It coincided with the moon’s closest approach to Earth, known as perigee, making it a “supermoon” as well. “Supermoons” will also occur in September, October and November.
At its perigee, the moon is about 357,000 km from Earth’s center, appearing larger in the sky than during apogee (its farthest point) when it is about 406,000 km away.
August’s full moon is typically called the “Sturgeon Moon.” That name was given to it by early Native American tribes living around the Great Lakes, which caught sturgeon fish at this time of year.
A phenomenon called Raleigh scattering explains why the full moon looks orange as it appears on the eastern horizon during dusk. Precisely because it is viewed close to the horizon, a full moon is viewed through the thickest part of Earth’s atmosphere. Reddish light more easily travels through because its longer wavelength means it strikes fewer particles.
Although a full moon is a beautiful sight, it’s best observed when it’s less bright. When it’s less than full, there’s also a line called the terminator—where day meets night—which allows observers to see shadows cast from the east to the west on the lunar surface.
A full moon occurs every month as our natural satellite orbits Earth. At one point, it is on the opposite side of the Earth to the sun, so its entire disk is fully illuminated. The moon will now enter its waning gibbous phase, during which it will rise later and seem less illuminated. It will drop in brightness as its eastern limb falls into shadow.
In two weeks, it will reach a new moon, which is roughly between Earth and the sun, so it’s lost in its glare for a few days before emerging as a crescent in the west in the post-sunset night sky.
The next “blue moon” will be on May 31, 2026, when a “monthly blue moon” will occur. The following “seasonal blue moon” will occur on May 20, 2027.
The next full moon will be the full “Super Harvest Moon Eclipse” on Wednesday, September 18—the ninth of the 12 full moons in 2024. As well as being a “supermoon,” it will partially pass through Earth’s outer shadow in space.
Pick up my books Stargazing in 2024, A Stargazing Program For Beginners, and When Is The Next Eclipse?
Wishing you wide eyes and clear skies.
