North American skywatchers can see the Moon turn a reddish hue as it flirts with Earth’s shadow on the night of May 15–16.
Diana Hannikainen, Observing Editor, Sky & Telescope
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Gary Seronik, Consulting Editor, Sky & Telescope
Susanna Kohler, Communications Manager and Press Officer, American Astronomical Society
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Note to Editors/Producers: This release is accompanied by high-quality graphics; see the end of this release for the images and links to download.
Almost one full year since the last total lunar eclipse, the sight of the Moon gliding into Earth’s shadow returns to grace the skies. Viewers in most of North America, all of Central and South America, western Europe, most of Africa, and the eastern Pacific Ocean will see the Moon darken and turn a reddish hue late in the evening on Sunday May 15th and into the wee hours of Monday May 16th.
What to Look For
The Moon charts a course through the southern half of Earth’s shadow, and totality is predicted to last for 85 minutes. Mid-eclipse happens on May 16th (4:12 Universal Time), about 1½ days before the Moon reaches perigee, the point in its orbit when it’s closest to Earth. On eclipse night, the Moon will appear around 12% larger than it does when it’s at apogee (farthest from Earth in its orbit), but likely only dedicated Moon watchers will notice this. The May 15–16 eclipse could be a fairly dark one, but look for a bit of brightening along the Moon’s southern limb.
Viewers will have the opportunity to see the summer Milky Way glowing nicely during totality as the overwhelming brightness of the full Moon is dimmed by Earth’s shadow.
The stages of the eclipse occur simultaneously for everyone, but not everyone will see the full eclipse. Weather permitting, observers in the eastern half of North America will witness the entirety of the event starting on the evening of May 15th, with the partial eclipse phase beginning about two hours after sunset for the East Coast and around one hour after sunset for the Midwest. On the West Coast, the Moon will be about to enter totality as it rises around sunset. And in the Northwest, the Moon rises as the later stages of the eclipse are already underway. Most of Alaska will have to sit this one out, though.
South America will see the whole show, starting on the evening of May 15th, while viewers in western Europe and Africa will have to set their alarms to enjoy the event in the hours before dawn on May 16th. For observers in the British Isles, the Moon sets as it’s fully immersed in Earth’s dark, inner shadow, whereas viewers in New Zealand will catch the tail end of the event on the evening of May 16th, as the Moon rises while it’s exiting Earth’s shadow.
The actual clock times of the eclipse phases depend on your time zone. See the table below and diagrams at the end for times of key events for the lunar eclipse:
|Penumbra first visible?||~2:00||~11:00 p.m.||~10:00 p.m.||~9:00 p.m.||—||—||—|
|Partial eclipse begins||2:28||11:28 p.m.||10:28 p.m.||9:28 p.m.||**8:28 p.m.||—||—|
|Total eclipse begins||3:29||*12:29 a.m.||11:29 p.m.||10:29 p.m.||9:29 p.m.||**8:29 p.m.||—|
|Mid-eclipse||4:12||*1:12 a.m.||*12:12 a.m.||11:12 p.m.||10:12 p.m.||9:12 p.m.||—|
|Total eclipse ends||4:54||*1:54 a.m.||*12:54 a.m.||11:54 p.m.||10:54 p.m.||9:54 p.m.||—|
|Partial eclipse end||5:56||*2:56 a.m.||*1:56 a.m.||*12:56 a.m.||11:56 p.m.||10:56 p.m.||**9:56 p.m.|
|Penumbra last visible?||~6:30||*~3:30 a.m.||*~2:30 a.m.||*~1:30 a.m.||*~12:30 a.m.||~11:30 p.m.||~10:30 p.m.|
Mechanics of a Lunar Eclipse
“A lunar eclipse happens when the Sun, Earth, and a full Moon form a near-perfect lineup in space, in what is known as syzygy,” says Diana Hannikainen (pronounced HUHN-ih-KY-nen), Observing Editor at Sky & Telescope. The Moon slides into Earth's shadow, gradually darkening, until the entire lunar disk turns from silvery grey to an eerie dim orange or red. Then events unfold in reverse order, until the Moon returns to full brilliance. The whole process will take about five hours and 20 minutes. You only need your eyes to see the drama unfold, but if you have binoculars or a backyard telescope, they'll enhance the view.
The events that happen during a total lunar eclipse are more complex and interesting than many people realize. The event has five stages, each with different things to watch.
(1) The Moon's leading edge enters the pale outer fringe of Earth's shadow: the penumbra. You probably won’t notice anything until the Moon is about halfway across the penumbra.
Watch for a slight darkening on the Moon's lower-left side as seen from North America. The penumbral shading becomes stronger as the Moon moves deeper in.
The penumbra is the region where an astronaut standing on the Moon would see Earth covering only part of the Sun's face.
(2) The Moon's leading edge enters the umbra, the cone of Earth's shadow within which the Sun’s completely hidden. You should notice a dramatic darkening on the leading edge of the lunar disk. With a telescope, you can watch the edge of the umbra slowly engulfing one lunar feature after another, as the entire sky begins to grow darker.
(3) The trailing edge of the Moon slips into the umbra for the beginning of total eclipse. But the Moon won't black out completely: It's sure to glow some shade of intense orange or red.
Why is this? The Earth’s atmosphere scatters and bends (refracts) sunlight that skims its edges, diverting some of it onto the eclipsed Moon. It’s the same effect that happens at sunset. If you were on the Moon during a lunar eclipse, you’d see the Sun hidden by a dark Earth rimmed with the reddish light of all the sunrises and sunsets ringing the world at that moment.
The red umbral glow can be quite different from one eclipse to the next. Two main factors affect its brightness and hue. The first is simply how deeply the Moon goes into the umbra as it passes through; the center of the umbra is darker than its edges. The other factor is the state of Earth's atmosphere. If a major volcanic eruption has recently polluted the stratosphere with thin global haze, a lunar eclipse can be dark red, ashen brown, or occasionally almost black.
In addition, blue light is refracted through Earth's clear, ozone-rich upper atmosphere above the thicker layers that produce the red sunrise-sunset colors. This ozone-blue light tints the Moon also, especially near the umbra's edge. You’ll need binoculars or a telescope to see this effect.
(4) As the Moon continues moving along its orbit, events replay in reverse order. The Moon's edge re-emerges into sunlight, ending totality and beginning a partial eclipse again.
(5) When all of the Moon escapes the umbra, only the last, penumbral shading is left. Some time later, nothing unusual remains.
Read more on this eclipse in the May 2022 issue of Sky & Telescope and on S&T's website: Witness A Total Lunar Eclipse on Sunday, May 15–16.
If it's cloudy where you are, you can follow a live stream of the eclipse on several sites. One is courtesy of Gianluca Masi and the Virtual Telescope website starting at 2:15 UT on May 16th (10:15 p.m. EDT on May 15th). Or you can head to Lowell Observatory's event starting at 10:15 p.m. EDT / 7:15 p.m. PDT on May 15th.
Read more on the Danjon scale and other things to look for during the eclipse.
Sky & Telescope is making the illustrations below available to editors and producers. Permission is granted for nonexclusive use in print and broadcast media, as long as appropriate credits (as noted) are included. Web publication must include a link to skyandtelescope.org.
Why does the Moon turn red? When the Moon falls in Earth’s shadow, not all sunlight is blocked. A sliver of light will travel through Earth’s atmosphere, refracting — or bending — toward the Moon to then reflect off its surface. For the same reason that the sky is blue, the blue wavelengths of sunlight are scattered in Earth’s atmosphere. Longer, redder wavelengths can pass through without scattering — this is the same phenomenon that turns the Sun red when it’s near the horizon. These photons are the ones that make it through to shine on the Moon. In a sense, the Moon is seeing all of Earth’s sunrises and sunsets all at once. Rollover the icons to see mid-eclipse views from Earth and from the Moon. Click for a high-resolution, annotated diagram.
Sky & Telescope
Why isn't every full Moon an eclipse? The Moon’s orbit around Earth is tilted a small amount, 5.14°, compared to the plane of Earth’s orbit around the Sun (exaggerated in the figure for clarity). That means that most times, as the Moon orbits Earth, it evades Earth’s shadow — and when the Moon is opposite the Sun, we see it as a full Moon on Earth, its whole disk shining. However, roughly twice a year, the full phase of the Moon coincides with a node, where the Moon’s orbital plane crosses Earth’s orbital plane around the Sun. Depending on how close the node is to the full Moon, we may see a partial or total lunar eclipse at those times. Use the slider to see how the setup changes.
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