The full moon of March, called the Worm Moon, will occur on Wednesday, March 20, at 9:43 p.m. EDT (0143 GMT on March 21), just under four hours after the vernal equinox — the moment when the length of day and night on Earth is nearly the same, marking the start of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. It will also come a day after the moon reaches perigee, the closest point to Earth, making the full moon a "supermoon," appearing slightly larger than the full moon usually does.
For observers on the U.S. East Coast, the moon will rise about 20 minutes before sunset by 7 p.m. local time on the evening of March 20, and moonset is the next morning around 7:30 a.m., according to the U.S. Naval Observatory. The moon will be in the constellation Virgo.
A full moon occurs when the moon is exactly on the opposite side of the Earth from the sun. The moon's is illuminated by the sun's light, unless its orbit carries it within the shadow of the Earth. That happened in January, and people on the night side of Earth saw a total lunar eclipse. That won't happen in March; the next lunar eclipse, in which the moon will be partially covered by the Earth's shadow, will be July 16 and not visible in the Western Hemisphere. Most full moons "miss" Earth's shadow, because the moon's orbit is tilted (or inclined) five degrees with respect to the plane of the Earth's orbit, so the sun, Earth and moon aren't always lined up perfectly.
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What makes the 'Worm Moon' super?
Though there won't be a lunar eclipse in March, the full moon will be a "supermoon" – appearing about 10 percent larger than average. On March 19, at 3:47 a.m. EDT (0747 GMT), the moon will reach perigee, the closest point to Earth in its orbit. On average, the moon is about 240,000 miles (385,000 kilometers) from the Earth. At perigee, that distance is about 350,000 km (220,000 miles), whereas at apogee it is about 406,000 km (250,000 miles). This happens because the orbit isn't a perfect circle. For all but the most careful observers, the size difference is too small to notice with the naked eye.
Through binoculars or a small telescope the full moon appears very bright; enough that one can still see it with sunglasses. There is no danger to one's eyesight, but details on the lunar surface can be difficult to see due to the lack of contrast. A full moon means we are looking at the surface of the moon at noontime, when there are no shadows at all towards the center of the disk, and few even towards the edges (if one were standing on the center of the moon's face, the sun would be directly overhead). Moon filters are available that can make some features stand out better. Waiting a few days after the full moon or observing a few days before also makes it easier to see the surface features. This is especially true towards the edge of the lunar disk.
Regulus meets the Worm Moon
Two days before the full moon, on March 18, the moon will be in conjunction (sharing the same celestial longitude) with Regulus, the brightest star in the constellation Leo. The moon will appear to pass about five lunar diameters (about 2.6 degrees) north of the star. The conjunction occurs at 7:59 p.m. EDT (2359 GMT).
In New York City the moon will be up already, as it rises at 4:17 p.m. local time. Observers in the Midwest cities such as Chicago will be able to catch the pairing as well, though not the moment of conjunction. Moonrise there is at 4:13 p.m. and the conjunction occurs at 5:59 p.m., while sunset is at 7 p.m. By the time the sun goes down enough to see Regulus, between 8 p.m. and 8:30 p.m., the moon will still be in Leo, and close to the star, about three degrees away.
Waning moon passes Jupiter
Another conjunction coming this month will be between the moon and Jupiter. On Tuesday, March 26 at 10:28 p.m. EDT (0228 GMT on March 27), a day before the moon reaches first quarter (or "half") phase, it will meet up with Jupiter in the constellation Ophiuchus, passing about 1.5 degrees north of the giant gas planet, according to the skywatching website In-the-Sky.org.
The moment of conjunction will be before the moon and Jupiter rise, but they will be near each other when they rise at about 2:30 a.m. on March 27. By sunrise (which is 6:48 a.m.) at they will both be about 24 degrees above the horizon, so catching them should be relatively easy for those who stay up late.
The full moon tends to wash out fainter constellations, but in March the bright winter constellations of Orion, Canis Major, Taurus and Gemini are still visible, and in fact are higher in the early evening in the east-southeast.
A moon of many names
March full moon names reflect local lore; the "Worm Moon" moniker (per the Old Farmers Almanac) comes from the ground becoming warmer and moist, prompting the return of earthworms and with them, birds.
According to the Ontario Native Literacy Coalition, the Ojibwe (or Aanishnabeg) peoples called it Ziissbaakdoke Giizis, meaning the "Sugar Moon," after the sap that flows in maple trees. It also marks the Aanishnabe new year. The Cree called it the Mikisiwipisim, or the "Eagle Moon," as the eagles returned from their seasonal migration. Both Aanishnabe and Cree traditions reflect the environment in northeastern North America, where the two peoples live.
The Haida of the Pacific Northwest call the March full moon Xitgaás Kungáay, or "Noisy Goose Moon," according to the Tlingit Moon and Tide Teaching Resource published by the University of Alaska at Fairbanks – a number of migratory species are endemic to the region.
In the Southern Hemisphere, March marks the transition from summer to autumn, and the Māori of New Zealand described the lunar month in March to April (as measured between the successive new moons, with the full moon halfway between) as Paengha-whāwhā, which means "all straw is now stacked at the borders of the plantations," according to the Encyclopedia of New Zealand.
In China, the traditional lunar calendar calls the March lunation the second month, Xìngyuè, or Apricot Month, for when the eponymous trees blossom.
For the Jewish people, March 20 marks the beginning of the holiday of Purim, (the 14th day of the lunar month of Adar), which celebrates Esther saving the Jews of Persia from a plot by one of the king's advisers to exterminate them.
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