The full moon of March, called the Worm Moon, will occur in the eastern U.S. during the afternoon hours of March 9, about 13 hours before reaching perigee, the nearest point from Earth in its orbit. This will create a "supermoon," a full moon that appears slightly larger than average.
The moon becomes officially full for observers on the East Coast of the U.S. on March 9 at 1:48 p.m. EDT (1748 GMT), according to NASA's SkyCal. In New York City, moonrise is at 7:01 p.m. the evening of March 9 and moonset is the next morning at 8:07 a.m., according to timeanddate.com. The sun sets the evening of March 9 at 6:56 p.m.
The moon will be in the constellation Leo, and it will have an angular diameter, or apparent size, of 33 arcminutes across, compared to an average of 31 arcminutes (one degree is equivalent to 60 arcminutes). So, the difference in size won't be noticeable to most observers.
What is a supermoon?
The reason the moon will appear larger is that it reaches perigee the day after the full moon, at 2:33 a.m. EDT (0633 GMT).. The moon's orbit isn't a perfect circle, and at perigee it will be 223,980 miles (360,461 kilometers) from the Earth, versus its average distance of 240,000 miles (384,400 km).
When the full moon coincides with perigee it is sometimes called a "supermoon" — but in this case the full moon will miss perigee by about a day and a half. That said, "supermoon" isn't an term used by astronomers, and whether a full moon counts as "super" often depends on how close to the official full moon the user of the word thinks perigee should be.
How to observe the Full Worm Moon
The full moon occurs when the moon is on the opposite side of the Earth from the sun. Most of the time, the full moon is illuminated by the sun's light, but occasionally the moon's orbit carries it within the shadow of the Earth, resulting in a lunar eclipse. The March full moon will "miss" the Earth's shadow, because the moon's orbit is inclined five degrees with respect to the plane of the Earth's orbit, and therefore the Earth won't be directly between the sun and the moon this time.
Through binoculars or a small telescope, the full moon appears so bright it can be hard to spot any detail, because there are no shadows to give any contrast. If one were standing on the moon, it would be noon — from such a lunar observer's perspective the sun would be directly overhead. Moon filters are available that can make some features stand out, but if you wait a few days after the full moon or observe it a few days before, shadows bring out more detail.
Being in the constellation Leo, the moon will be about halfway between the star Regulus, the brightest in that constellation, and Spica, the brightest star in the constellation Virgo. It will be just south of Denebola, the second-brightest star in Leo that marks the lion's tail.
Venus meets up with Uranus
On March 9 the planet Venus, which is a prominent "evening star," will make a close pass to the planet Uranus. Uranus is usually only visible to observers with a very keen eye and dark skies — it is between magnitude 5 and 6, which puts it near the limits that most people can see without the aid of binoculars or a telescope.
At 10:36 a.m. EDT (1436 GMT), Venus will pass 2 degrees and 24 arcminutes north of Uranus, and the two objects will be in conjunction, meaning that they share the same celestial longitude. Both will be in the constellation Aries. The two planets will still be close in the evening sky, becoming visible at dusk. Venus is by far the brighter of the two, and a good pair of binoculars can show both in the same field of view, though from urban locations light pollution may make Uranus less visible. From New York, Venus is clearly visible in the southwest by about 7:30 p.m. local time, though the actual conjunction will have passed by then.
Observers in time zones ahead of Greenwich will see it as night falls. For example, in Tehran the conjunction happens at 6:06 p.m. local time, and that is exactly when the sun sets. As one moves further east, conditions get more favorable — in New Delhi the conjunction occurs at 8:06 p.m. local time and Venus sets at 9:49 p.m., according to skywatching site In-the-Sky.org.
Spot the winter constellations
The March full moon shares the sky with bright winter constellations, which are notable for the fact that they start to set by midnight, making way for the stars of summer.
The southern half of the sky in mid-northern latitudes is dominated by Leo, which is framed by Boötes to the east (the left as one faces south) and Gemini to the west (the right). From a dark-sky location, observers can trace Hydra, which makes a line of faint stars that runs diagonally up from east to west.
How the "Worm Moon" got its name
According to the Ontario Native Literacy Project, the Ojibwe (or Anishinaabe) peoples called the full moon of March Ziissbaakdoke Giizas, or the Sugar Moon, as March is when the maple sap begins to run. The Cree called it the Mikisiwipisim, or the Eagle Moon.
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 falls during late summer and early 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 9 marks the beginning of the holiday of Purim, (the 14th day of the lunar month of Adar), celebrating Esther's saving the Jews of Persia from a plot by one of the king's advisors to exterminate them.
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