On the night of Sunday, January 20, sky-watchers across the Americas will have a front-row seat to a rare cosmic event, as three lunar phenomena converge to give rise to what some people are calling a super blood wolf moon.
While that may sound like a song straight out of a 1970s rock opera, it’s actually a term for a type of total lunar eclipse.
During totality, the full moon does not disappear entirely and instead turns a rusty shade of red, earning it the moniker “blood moon.” This lunar eclipse happens to coincide with the wolf moon, the traditional name for the January full moon. What's more, the moon will be unusually close to Earth and so will be slightly bigger and brighter, making it a so-called supermoon. (Here are some of the top places to see the super blood wolf moon.)
The entire eclipse will last nearly 3.5 hours, starting with the partial eclipse phase, when Earth’s shadow takes its first bite out of the moon, at 10:34 p.m. ET (03:34 UT). The last hint of this shadow will leave the lunar disk at 1:51 ET (06:51 UT). Totality will last a full 63 minutes, with the maximum eclipse—when the moon is at its deepest, most dramatic coloration—occurring at 12:12 a.m. ET (05:12 UT).
How do all of these lunar spectacles work, and how can you catch a glimpse? We’ve got you covered.
What happens during a total lunar eclipse?
For thousands of years, lunar eclipses have garnered both awe and fear. But once science had explained the celestial mechanics at play, astronomers could predict when they will occur and where they will be visible.
In a lunar eclipse, Earth casts a shadow on the moon. This doesn't happen every time the moon makes its monthly trek, though; the moon's orbit is tilted, so it usually glides above or below Earth's cone-shaped shadow.
Total lunar eclipses are even more rare. They happen only during a full moon, and only when the sun, Earth, and moon are precisely aligned so that the darkest part of our planet's shadow completely blankets the lunar disk. This usually happens twice a year, on average, and each total eclipse can be seen from only one hemisphere of Earth.
The last total eclipse of the moon occurred on July 27, 2018, and was visible across Africa and parts of Asia. This year’s total eclipse will be the first to be seen in its entirety in North America in nearly three and half years. Americans missing this one will have to wait until May 26, 2021, to get their next chance at viewing a blood moon.
What makes the moon turn red?
During the total eclipse, sunlight shining through Earth's dusty atmosphere is bent, or refracted, toward the red part of the spectrum before it’s cast onto the moon's surface. As a result, expect to see the lunar disk go from a dark gray color during the partial phase of the eclipse to a reddish-orange color during totality.
The moon's color during totality can vary considerably depending on the amount of dust in the atmosphere at the time. Active volcanoes spewing tons of ash into the upper atmosphere, for instance, can trigger deep blood-red eclipses. However, no one can predict exactly what color we'll see before each eclipse.
Why is it also a super wolf moon?
According to the Old Farmer’s Almanac, Native Americans and colonial Europeans dubbed the January full moon the wolf moon, because wolves in the region would purportedly start howling in hunger due to midwinter paucity.
This month’s wolf moon eclipse is even more special because the lunar disk will appear to be slightly larger than usual. The moon will be at perigee—its closest point to Earth—just 59 minutes before the height of the eclipse. This will make the lunar disk appear 13 percent larger and about 16 percent brighter than the average full moon.
The January supermoon also happens to kick off a triad of supermoons in 2019, with the next ones arriving on February 19 and March 21.
Can I see the super blood wolf moon?
Sky-watchers across the entire Western Hemisphere will be able to see all or part of the eclipse. North America, Central America, and South America will get to see all the phases of this special sky show, as the moon rides high in the eastern sky. Meanwhile, stargazers in western Europe and most of Africa will be able to watch during the early morning hours, local time, on the 21st.
Unfortunately, folks in Asia and Australia will be on the wrong side of the planet when the eclipse is under way.
Unlike solar eclipses, lunar ones are safe to watch with the naked eye. But if the sky is too cloudy or you're in the wrong time zone, you can still take part in the lunar disappearing act online: Astronomers Without Borders will webcast the eclipse from various locations starting at 10:30 p.m. ET.
This story was originally published January 18.