The full moon of May, also called the Flower Moon, will occur the morning of Thursday, May 7, at 6:45 a.m. ET, according to NASA's SkyCal site. This full moon will come just two days after the moon reaches perigee, or the closest point to Earth in its orbit, making this a "supermoon," according to NASA.
Perigee occurs May 5 at 11:03 p.m. ET. That will make the moon appear ever-so-slightly larger than usual, though it would take very careful measurements to see the difference. When perigee coincides with the full moon it is sometimes called a "supermoon," but that isn't a real astronomical term — and there is some debate about how closely a full moon must coincide with perigee to qualify as a supermoon.
Supermoons can appear up to 7 percent larger and 15 percent brighter than the typical full moon. On average, the full moon measures about 31 arc minutes, or 0.52 degrees wide in the night sky, and on May 7 it will be about 33 arc minutes (0.55 degrees) across. For reference, your clenched fist held at arm's length measures about 10 degrees wide.
Observers in New York City will see moonrise at about 8:26 p.m. local time on May 7, or about an hour and a half after sunset, according to timeanddate.com. The moon will be in the constellation Libra. Early risers on May 7 will see the sun rise at 5:46 a.m. local time while the moon sets at 6:06 a.m., so the two will share the sky for a short while. This phenomenon will occur for observers in a relatively wide range of latitudes — in Miami, for example, the sun rises at 6:39 a.m. on May 7, while the moon sets at 6:53 a.m. local time.
From Southern Hemisphere locations such as Cape Town, South Africa, the full moon occurs at 12:45 p.m. local time (during the day). Moonrise is at 6:19 p.m. local time, and sunset is at 5:59 p.m., so the sun and moon won't be in the sky at the same time. This has to do with the relative placement of the sun and moon along the ecliptic, the line in the sky projected by Earth's orbit, and the fact that in the Southern Hemisphere days are shorter because we are approaching winter.
The full moon occurs when the moon is exactly on the opposite side of the Earth from the sun. The moon reflects the sun's light to Earth, unless its orbit carries it within the Earth's shadow — a lunar eclipse.
Through binoculars or a small telescope the full moon appears very bright, so much that the glare can even require filters. Unlike observing the sun (which one should never do without specialized equipment), there is no danger to one's eyes when observing the bright moon, but details can be harder to see than when the moon is a crescent or during quarter phases ("half" moons).
The reason is that a full moon means we are seeing the surface at lunar noontime (if one were standing on the moon the sun would be directly overhead). There are no shadows towards the center of the disk, and few of them even towards the edges. Moon filters are available that can make some features stand out, or one can simply wait a few days after the full moon or observe a few days before, when shadows make spotting the surface features easier.
Venus on May 7 will still be high in the western sky for observers in mid-northern latitudes at sunset. From New York the planet will be about 25 degrees above the horizon in the constellation Taurus and won't set until 10:58 p.m. local time, according to heavens-above.com. Venus is bright enough that it is often one of the first "stars" to be visible after sunset, and the planet was shining at its brightest of the year just last week.
From Cape Town, Venus sets earlier, at 7:39 p.m. local time on May 7, but the sun sets earlier too, so the planet will still be an easy naked-eye target.
Mars, Jupiter and Saturn will still be grouped in the sky as early-morning planets, rising on the morning of May 8 at 2:38 a.m., 1:03 a.m. and 1:18 a.m. local time, respectively, in New York. They will all be between 20 and 30 degrees above the horizon by 5 a.m. local time, making a rough line in the southeastern sky.
Southern Hemisphere observers will have a much better view — from Cape Town, at 5 a.m. on May 8, the lowest of the three planets will be Mars, at 57 degrees in altitude, while Jupiter and Saturn will be at 77 and 75 degrees, respectively. Here the relative angle the ecliptic makes with the horizon is the reason, and the later sunrise also works in favor of planets getting higher in the sky before it gets light out.
How the "Flower Moon" got its name
The full moon of May is often called a Flower Moon, and the term comes from the blooms that appear in North America around that time; many Algonquin-speaking peoples in the northeastern part of the continent called it something similar, such as the Ojibwe (or Anishinaabe), according to the Ontario Native Literacy Coalition. The Cree called it the Frog Moon, as May is when frogs tend to become active. Both Anishinaabe and Cree traditions reflect the environment in northeastern North America, where the two peoples live.
Related: Full moon names (and more) for 2020
The May full moon will also mark the halfway point of the month of Ramadan, when observant Muslims fast from sunrise to sunset. In the Islamic and Jewish calendars months begin and end with new moons, so Ramadan will end on May 24.
In the Southern Hemisphere, the Māori described the lunar month of Pipiri, which occurs from May to June: "all things on earth are contracted because of the cold," according to the Encyclopedia of New Zealand.
Editor's note: If you have an amazing supermoon photo you'd like to share for a possible story or image gallery, you can send images and comments to firstname.lastname@example.org.
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