On Friday morning EDT, skywatchers will get to experience a partial lunar eclipse, with November's Beaver full moon taking on a reddish hue. What observers see in the sky will depend on where they are.
However, anyone can enjoy the partial lunar eclipse thanks to astronomy group The Virtual Telescope, who will be live streaming the astronomical event in the video shown below.
The partial lunar eclipse will be visible by the naked eye in various regions of the globe, including North America, eastern Australia, New Zealand, and Japan. It will begin at 1:02 a.m. EDT when the moon slips into Earth's penumbra, the outer part of its shadow. By 3:45 a.m. it will have passed into the inner, darker shadow, the umbra, by around 95 percent.
The peak of the eclipse will happen at 4:03 a.m. This is the best time to see the Beaver Moon—the name given to November's full moon—as a "Blood Moon," as this will be the point when the red coloration is most visible.
This will be the longest partial lunar eclipse for at least a century, lasting 3 hours, 28 minutes, and 23 seconds. The eclipse's duration makes it the longest astronomical event of this type for 580 years, according to the Holcomb Observatory at Butler University.
Why is it called a Blood Moon?
The title of "Blood Moon" is normally reserved for total lunar eclipses, but because 99.1 percent of the moon will be within the darkest part of Earth's shadow, this partial eclipse is almost total enough to warrant that label, according to NASA.
During this eclipse, just a tiny sliver of the moon will be visible, with the vast majority disappearing into Earth's shadow as the sun and moon pass opposite sides of the planet.
The moon will appear red thanks to a process called Rayleigh scattering, the same physical process that causes the sky to appear blue.
Light coming from the sun is made up of all different colors. These colors of light take a specific order— red, orange, yellow, green, blue, indigo, and violet—because of the size of their wavelength and their frequency.
Red light has a long wavelength and a low frequency, and blue light has a short wavelength and a high frequency. Because of this, when the sun is directly overhead, red photons—and the individual particles that comprise light—stream through our atmosphere and reach the ground almost unhindered.
The story is different for blue photons, however. The short wavelength of blue photons means that they strike atoms in the upper atmosphere and are scattered away. As a result, before a blue photon hits your eye, it has "bounced" around the sky making the sky appear blue.
The situation is different when the sun is on the horizon. Because its light then has much more atmosphere to travel through, the red photons begin to be scattered. That's why the sky appears red at sunset sometimes.
In the case of a lunar eclipse, because the Earth is in between the sun and the moon, photons from the sun have to pass through Earth's atmosphere before they can reach the moon and be reflected.
This means, just like when red photons have to pass through the deeper atmosphere at the horizon, there is more chance of even long-wavelength red light being scattered.
If you miss November's partial eclipse, you won't have to wait too long to see another Blood Moon. Just as 2022 had two lunar eclipses, 2023 will experience two. The first falls on the 15/16 of May, the second occurs on 7/8 November.
Unlike 2022's two partial lunar eclipses, the 2023 eclipses will both be total lunar eclipses, however.
