The world will have to wait until 2669 for another eclipse of comparable length.
En las primeras horas del 19 de noviembre de 2021, la Luna se adentrará en la sombra de la Tierra durante tres horas y veintiocho minutos, protagonizando el eclipse lunar parcial más largo del siglo. El fenómeno, visible a simple vista desde las Américas y luego desde Europa y Asia, cubrirá el noventa y siete por ciento del disco lunar. Es uno de esos momentos en que el cosmos recuerda a la humanidad su lugar en una danza celestial que lleva siglos repitiéndose, y que no volverá a ocurrir con esta magnitud hasta el año 2669.
- El 19 de noviembre, la Luna desaparecerá casi por completo durante más de tres horas, un espectáculo que no se repetirá en esta escala durante más de seis siglos.
- El eclipse parcial cubrirá el 97% de la superficie lunar, situándose en el límite de lo que podría haber sido un eclipse total, lo que lo convierte en un evento astronómico excepcionalmente raro.
- Millones de personas en las Américas podrán observarlo en las horas previas al amanecer sin ningún equipo especial, mientras que Europa y Asia lo verán al caer la noche.
- A diferencia de los eclipses solares, que exigen desplazarse a una franja estrecha del planeta y usar protección ocular, este fenómeno es accesible para cualquiera que tenga cielos despejados y levante la vista.
En la madrugada del 19 de noviembre de 2021, la Luna se deslizará hacia la sombra de la Tierra y permanecerá allí durante tres horas, veintiocho minutos y veintitrés segundos. Se trata de un eclipse lunar parcial tan extenso que cubrirá el noventa y siete por ciento del disco lunar, convirtiéndolo en el más largo del siglo. Será visible a simple vista desde las Américas durante las primeras horas de la mañana, y más tarde desde Europa oriental y Asia. El mundo no volverá a presenciar algo comparable hasta el año 2669; el último eclipse de duración similar ocurrió en 1440.
Un eclipse lunar se produce cuando la Tierra se interpone entre el Sol y la Luna, proyectando su sombra sobre la superficie lunar. Esa sombra tiene dos zonas: la umbra, oscura e interior, y la penumbra, más tenue y exterior. Cuando la Luna entra completamente en la umbra, se produce un eclipse total, y la Luna suele adquirir un tono rojizo o cobrizo —el llamado eclipse de sangre— porque la atmósfera terrestre desvía la luz solar hacia ella. En un eclipse penumbral, el oscurecimiento es tan leve que puede pasar desapercibido. El de noviembre es parcial: la Luna penetra en la umbra sin llegar a sumergirse del todo, dejando una fina franja iluminada.
Los eclipses lunares solo ocurren cuando las órbitas del Sol y la Luna se alinean en el mismo plano, una condición poco frecuente. La mayoría de los años registran dos eclipses lunares, aunque algunos no tienen ninguno. De todos ellos, apenas el veintinueve por ciento son totales. La duración habitual ronda los cien minutos; por eso, las más de tres horas del eclipse de noviembre resultan extraordinarias.
A diferencia de los eclipses solares —que solo son visibles desde una franja estrecha de la Tierra, duran apenas unos minutos y requieren gafas especiales para no dañar la vista—, los eclipses lunares pueden contemplarse desde cualquier punto del hemisferio nocturno sin ninguna protección. El de noviembre será, en ese sentido, un regalo para quienes tengan cielos despejados y la paciencia de mirar hacia arriba.
On the morning of November 19, 2021, the moon will slip into Earth's shadow and stay there longer than it has in a century. For three hours, twenty-eight minutes, and twenty-three seconds, the lunar disk will darken as our planet blocks the sun's light, a partial eclipse so extensive that it will cover ninety-seven percent of the moon's face. The event will be visible to the naked eye across the Americas during the early morning hours, and later that same night it will appear in the skies above eastern Europe and Asia. After this, the world will have to wait until 2669 for another eclipse of comparable length.
A lunar eclipse happens when Earth positions itself directly between the sun and the moon, casting a shadow across the lunar surface. The mechanics are straightforward, but the specifics matter. Earth's shadow has two distinct regions: the umbra, which is the dark inner cone, and the penumbra, the fainter outer region. Depending on which part of the shadow the moon passes through, astronomers classify eclipses into three types. A total lunar eclipse occurs when the moon enters the umbra completely, disappearing into Earth's darkest shadow. During these events, the moon often glows a deep red or copper color—a phenomenon called a blood moon—because Earth's atmosphere bends sunlight around the planet and onto the lunar surface, much the way a sunset colors our own sky. A penumbral eclipse, by contrast, is subtle; the moon passes only through the penumbra and dims so slightly that casual observers might mistake it for an ordinary full moon. The November eclipse falls into the third category: a partial eclipse, where the moon dips into the umbra but not completely, leaving a thin sliver of the lunar disk still exposed to direct sunlight.
Lunar eclipses are relatively rare events. They occur only when the orbits of the sun and moon align in the same plane—a condition that happens infrequently. Most years see two lunar eclipses, though some years bring three and others bring none at all. Of all lunar eclipses, only about twenty-nine percent are total; the partial and penumbral varieties are more common. When a total lunar eclipse does occur, it can be seen from anywhere on Earth's night side, making it a genuinely global phenomenon. The typical duration of a lunar eclipse is around one hundred minutes from start to finish, as the moon travels through the penumbra, then the umbra, then back out through the penumbra again. The November eclipse will be exceptional: at three hours and twenty-eight minutes, it will be the longest partial eclipse in recorded memory. NASA's records show that an eclipse of similar duration last took place in 1440.
Solar eclipses, by contrast, operate on entirely different principles and follow different rules. A solar eclipse occurs when the moon passes in front of the sun, blocking its light and casting a shadow on Earth. This can only happen when the moon is in its new phase, positioned directly between Earth and the sun. The moon's shadow, however, is relatively small—it traces a narrow path across the planet's surface. This means a solar eclipse is visible from only one location at a time, and only for a few minutes. The same spot on Earth will not experience another solar eclipse from that same moon for approximately three hundred seventy-five years. Solar eclipses also require special precautions for safe observation; looking directly at the sun during a solar eclipse can cause permanent blindness, which is why observers must use specially designed solar glasses. Lunar eclipses pose no such danger; the moon is already dark, and watching it darken further requires no protection whatsoever.
The November eclipse will be a gift to observers across the Western Hemisphere. In the Americas, it will unfold during the predawn hours, when the moon hangs low in the western sky. Those in Europe and Asia will catch the final stages as evening falls. Unlike a solar eclipse, which demands travel to a specific path and precise timing, this lunar eclipse will be accessible to anyone with clear skies and a view of the moon. It is a reminder that the cosmos still offers free spectacles to those patient enough to look up.
Notable Quotes
Although technically a partial lunar eclipse, it will appear as a total eclipse— Time and Date
A similar eclipse only occurred in 1440 according to NASA's lunar eclipse records— NASA
The Hearth Conversation Another angle on the story
Why does this particular eclipse matter so much? Eclipses happen fairly regularly, don't they?
This one is extreme in a specific way. It's not a total eclipse—the moon doesn't fully enter Earth's darkest shadow. But it gets so close that ninety-seven percent of the moon will be covered. That combination of being almost-total but technically partial, and lasting over three hours, is what makes it rare. The last time something this long happened was 1440.
So it's the duration that's the real story here, not the type of eclipse itself.
Exactly. A typical lunar eclipse lasts about an hour and forty minutes. This one will be nearly double that. The moon will be creeping through Earth's shadow so slowly that observers will actually be able to watch it happen in real time.
And it's visible from most of the world, unlike a solar eclipse?
Right. Anyone on the night side of Earth with clear skies can see it. A solar eclipse is locked to a narrow path—you have to be in exactly the right place. A lunar eclipse is democratic. You just need to be awake and look up.
Why is that difference so fundamental?
It comes down to size and position. The moon is small relative to Earth, so its shadow only touches a tiny spot on our planet. But Earth is much larger than the moon, so Earth's shadow is huge. When the moon passes through it, the shadow covers the entire lunar disk from any vantage point on Earth's night side.
What will people actually see when they look at the moon that night?
For most of the eclipse, the moon will appear dark—not black, but a deep gray or reddish tone, depending on how much of it is in the umbra. The edge that remains in sunlight will be bright. So you'll see a crescent of light against a darkened disk. It's subtle but unmistakable if you know what you're looking for.