The glow of sunset will paint the moon red next month as a total lunar eclipse creates a “Blood Moon,” just days before the vernal equinox marking the start of spring. During the event, the moon will pass through Earth’s shadow, darkening in colour as the eclipse reaches totality.
Totality is the maximum phase of a total lunar eclipse when the entire moon is in the darkest part of Earth’s shadow. This is called the umbra, while the part of the shadow that’s a little lighter is the penumbra.The lunar eclipse will fall on the night of March 13 and last until early morning on March 14. Observers in the Americas and Greenland will enjoy the best view, as the Western world gets to watch the entire eclipse unfold from start to finish. Hopefuls elsewhere—in Western Europe, Western Africa, Eastern Russia, Japan, Australia, and Antarctica—might only see some of it.
The event differs from a partial lunar eclipse—and even more from a solar eclipse. In total lunar eclipses like this one, the moon is fully engulfed within the darkest area of Earth’s shadow, the conical-shaped umbra, where no direct sunlight reaches.
Partially eclipsed moons only graze this umbra and are less significant. Far less dramatic are penumbral eclipses, where the moon enters a paler region called the penumbra and light from the sun still partly reaches the moon from behind planet Earth.
Solar eclipses are a different species, yet there are similarities. Lunar and solar eclipses both involve the Earth, moon, and sun lining up. In lunar eclipses, Earth is in the middle, casting shade on the moon and causing it to darken noticeably at night.
In solar eclipses, the moon is in the middle, obstructing the sun’s light from reaching the Earth.
Lunar eclipses don’t require eye protection the way solar eclipses do, and while binoculars aren’t necessary, they may enhance the view of a lunar eclipse.
Eclipse Step by Step
On the night of the eclipse, the full moon will rise to the east as the sun is setting, since the sun and moon are directly opposite each other during eclipses and full moons.The spectacle will progress from constellation Leo the Lion to Virgo, between the bright stars Regulus and Spica, and then advance something like this:
First, at 11:57 p.m. EST, a penumbral eclipse begins as the moon enters Earth’s penumbral shadow.
Next, at 1:09 a.m. EST, a partial eclipse begins as the moon eases behind the conical umbra.
At 2:26 a.m. EST, totality begins; the moon is fully immersed in the umbra (though it will not cross the umbral axis–the centreline of the umbra).
At 2:58 a.m. EST, the instant of greatest eclipse is reached, with the March full moon, or “Worm Moon,” occurring at exactly 2:55 a.m. EST, just three minutes before the eclipse.
At 3:32 a.m. EST, totality ends, as the moon partially exits the umbra.
At 4:48 a.m. EST, the partial eclipse ends, as the moon exits the umbra entirely.
Finally, at 6 a.m. EST, the penumbral eclipse ends, with the moon exiting Earth’s shadow entirely.
Rust-Red Hue
It will be obvious when totality is reached, as the full moon will dim and take on a deep, rust-red hue. The reason? Although no direct sunlight reaches the umbra, diffused light from our atmosphere will cast a glow. In effect, all the sunsets and sunrises on Earth will shine upon the moon’s surface at once, bathing it in red. That’s what causes blood moons.The question “why is the sky blue?” ties into this. The answer is: the diffusion of light. While sunlight is white and contains all wavelengths, blue light scatters relatively easily. So when sunlight enters the atmosphere at a low angle, say, at sunset, the blue light has to pass through much more atmosphere and gets filtered out, leaving only reddish-orange to tint the moon with twilight.
An anomaly about next month’s event is that the moon won’t darken uniformly, because, although fully engulfed by the umbra, the eclipse won’t be “central”—it won’t hit the umbral axis. So, the northern limb of the moon will look slightly paler.
To top it off, it will be an unusually small moon. Since the moon’s orbit is elliptical, not round, it isn’t equidistant from Earth, so sometimes it’s farther away and appears smaller. Its farthest position from Earth will be reached just 3.4 days before the eclipse, making it a micromoon, one of three in 2025.
The eclipse will be the first of two this eclipse season. A partial solar eclipse will follow on March 29. That’s because when the orbital planes of the moon and Earth are already aligned nearly flat, as they will be in March, a solar eclipse is just as likely as a lunar one. In fact, they’re expected. Notably, the two eclipses will hug the spring equinox, March 20.
Eclipse seasons come about six months apart, so the second eclipse season will be in September. The reason eclipse seasons occur is because the moon’s orbital plane is slightly askew with Earth’s, meaning the moon often misses the cone of Earth’s shadow.
But just as spring, summer, fall, and winter arrive naturally when the timing and Earth’s axial tilt are just right, so too will eclipse seasons—eventually things line up.
