Matt Cardy/Getty Images
- On January 31, the full moon will be the second in a month, making it a blue moon; it'll be at the part of the moon's orbit that defines a supermoon; and there will be a total lunar eclipse.
- The total lunar eclipse is the most exciting for astronomers - it can give the moon a reddish tint, which is why it's sometimes called a blood moon.
- To catch the eclipse, you'll need to look up at a certain time: early in the morning in the US, or later that night in other parts of the world.
Early in the morning on January 31 - if you are in the right part of the world - you'll be able to look up at the sky and see what you could call a "super blue blood moon."
That's a full moon happening at the part of the moon's orbit that's closest to Earth (known as a supermoon). This will also be the second full moon of a calendar month, which is commonly referred to as a blue moon by NASA and others.
Most excitingly, in certain parts of the world it'll be possible to see a total lunar eclipse, which can give the moon a reddish hue when the Earth comes between the sun and our satellite, hence the name "blood moon."
The last time all three of these events happened at the same time was almost 152 years ago. But terms like these can make these occurrences seem more dramatic than they are. Because of where the moon is in its orbit, this full moon will be about 14% brighter than normal - whether or not that qualifies as super is up to you (maybe the moon is always super). And blue moon is not a technical astronomical term - in fact, a different historical definition by the Farmer's Almanac would make that phenomenon more rare than NASA's definition.
But the lunar eclipse component of these three aligned events is fascinating for astronomers, since the rapid temperature changes that occur when the Earth blocks the direct light of the sun can reveal new aspects of the moon's surface.
"The whole character of the moon changes when we observe with a thermal camera during an eclipse," Paul Hayne of the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, wrote in a feature on the upcoming eclipse. "In the dark, many familiar craters and other features can't be seen, and the normally nondescript areas around some craters start to 'glow,' because the rocks there are still warm."
This information could also reveal potential landing sites for future moon expeditions.
When and where to look
To catch the eclipse, you'll need to look up at the right time: early in the morning in North America and the Eastern Pacific, evening for those in the Middle East, Asia, and Australia. (Most of Europe will unfortunately miss this part of the show.)
During a lunar eclipse, the moon transitions into partial shadow - penumbra - before going into full shadow - umbra - then back into penumbra, as seen in the graphic below.
The reddish color it takes on has to do with the way that Earth's atmosphere breaks up light - much of the blue gets filtered out before the remaining light makes its way to the moon.
Viewers on the East Coast of the US will only be able to see the start of the time when the darker "umbra" of Earth's shadow covers the moon, at about 6:48 a.m., since the sun will rise shortly after that.
In the western US, the show will be better. For those on central time, NASA reports that the best viewing will be from about 6:15 a.m. to 6:30 a.m., with Earth's reddish shadow clearly visible on the moon before the sun comes up. Mountain time viewers will be able to catch the peak of eclipse at 6:30 a.m. local time. And viewers in California and further west will be able to see the event from start to finish, with totality beginning at 4:51 a.m. PT and ending at 6:05 a.m. PT.
If you're in the right place and you can get up early or stay up late, have a look.
NASA
Global map showing areas of the world that will experience (weather permitting) the Jan. 31, 2018 "super blue blood moon." The eclipse will be visible before sunrise on Jan. 31 for those in North America, Alaska and Hawaii. For those in the Middle East, Asia, eastern Russia, Australia and New Zealand, the "super blue blood moon" can be seen during moonrise the evening of the 31st.