This weekend is your next chance to catch the rare full blue moon before it again becomes "just a memory" until 2024.
A blue moon is the third full moon in a season containing four full moons, rather than the usual three, according to Sky & Telescope magazine. The sky phenomenon has been a cultural muse for music, art and language -- such as hit songs "When My Blue Moon Turns to Gold Again" and "Blue Moon," recorded by multiple artists including Elvis Presley, and the saying "once in a blue moon," which describes a rare event.
NASA has reported the first recorded use of "blue moon" occurring in 1528, while Sky & Telescope has traced the term's origin back to the Maine Farmers' Almanac published in the 1930s.
"Introducing the 'Blue' Moon meant that the traditional full Moon names, such as the Wolf Moon and Harvest Moon, stayed in (sync) with their season," said Diana Hannikainen, Sky & Telescope's observing editor, in a news release. This was before late amateur astronomer and Sky & Telescope contributor Hugh Pruett incorrectly understood the definition in 1946, and ultimately helped circulate the popular definition of blue moon: the second full moon within a month, the last of which occurred on Halloween 2020, according to Sky & Telescope.
People in the Americas will be able to see a nearly full moon Saturday night, before the true blue moon reaches its highest point in the sky early Sunday morning at 1:04 a.m. Eastern time, according to NASA. The moon will reach peak illumination at 8:02 a.m. Eastern time Sunday and appear close to full after dusk that day.
The full blue moon, which happens about once every 2.7 years on average, won't actually appear blue, though -- that only happens even more rarely, when "volcanic eruptions or forest fires send lots of smoke and fine dust into the atmosphere," according to Sky & Telescope.
This moon has had many different names. The Maine Farmers' Almanac first published Native Americans' terms for the full moons in the 1930s, according to NASA -- including the Algonquin tribes' "Sturgeon Moon," named after large fish that were more easily caught in the Great Lakes and other bodies of water during this time, and the "Green Corn Moon."
The name of the August full moon differs across cultures, however. The Anishnaabe people refer to it as the "berry moon," while the Cherokee people call it the "drying up moon." For the Comanche people, August's full moon is the "summer moon." The Creek people know it as the "big harvest" moon. And the Hopi people call it the "moon of joyful."
See all of the Native American names for this full moon on the Western Washington University Planetarium website.
Upcoming sky schedule
Throughout the remainder of 2021, you might be able to catch these space and sky events depending on your location.
The full moons and their names, according to The Old Farmer's Almanac:
- September 20: Harvest moon
- October 20: Hunter's moon
- November 19: Beaver moon
- December 18: Cold moon
Meteor showers, according to EarthSky's 2021 meteor shower guide:
- October 8: Draconids
- October 21: Orionids
- November 4-5: South Taurids
- November 11-12: North Taurids
- November 17: Leonids
- December 13-14: Geminids
- December 22: Ursids
Solar and lunar eclipses, according to The Old Farmer's Almanac:
- November 19: A partial eclipse of the moon, which people in North America and Hawaii will see between 1 a.m. Eastern time and 7:06 a.m. Eastern time.
- December 4: A total eclipse visible for those in the Falkland Islands, the southern tip of Africa, Antarctica and southeastern Australia.
When planets will be visible
Skywatchers will have multiple opportunities to spot the planets during certain mornings and evenings throughout the rest of 2021, according to the Farmer's Almanac planetary guide.
Seeing most of these -- except Neptune -- with the naked eye is possible, but binoculars or a telescope will provide the best view.
Mercury will appear as a bright star in the morning sky from October 18 to November 1. It will shine in the night sky from August 31 to September 21, and November 29 to December 31.
Venus, our closest neighbor in the solar system, will appear in the western sky at dusk in the evenings through December 31. It's the second-brightest object in our sky, after the moon.
Mars makes its reddish appearance in the morning sky between November 24 and December 31, and it will be visible in the evening sky through August 22.
Jupiter, the largest planet in our solar system, is the third-brightest object in our sky. Look for it in the evenings of August 20 to December 31 -- but it will be at its brightest until September 2.
Saturn's rings are only visible through a telescope, but the planet itself can still be seen with the naked eye in the evenings until December 31.
Binoculars or a telescope will help you spot the greenish glow of Uranus in the mornings through November 3 and in the evenings from November 4 to December 31. It will be at its brightest between August 28 and December 31.
And our most distant neighbor in the solar system, Neptune, will be visible through a telescope in the mornings through September 13 and during the evenings September 14 to December 31. It will be at its brightest until November 8.
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