Lunar Eclipse Over Morro Rock in Morro Bay, San Luis Obispo County, California, USA. This is a composite image. The moons were captured separately and overlayed into the image of Morro Rock captured at night. (Don Smith/Getty )
A rare perfect alignment of sun, Earth and moon will take place in the early morning hours of Tuesday, November 8, setting the stage for one of the most spectacular celestial events of the night sky: a total lunar eclipse.
The full moon will pass through the point in the sky exactly opposite the sun and be painted in inky darkness by Earth’s shadow.
The eclipse begins Tuesday morning at 12:02 a.m. PST, when the moon first encounters Earth’s partial, or penumbral, shadow. You may not see much of a change immediately, but over the next hour you can witness a subtle dimming of the full moon’s brightness.
The real show begins at 1:09 a.m., when the moon contacts Earth’s full shadow, the dark umbra blocking all sunlight. In the moments after, a prominent darkening will appear at the moon’s edge as the shadow nibbles away at the bright lunar disk. By 1:50 a.m., half of the moon will be consumed.
The climax of the eclipse, what's known as "totality," starts at 2:16 a.m. and will last almost an hour and a half. This is when the moon is fully engulfed in Earth’s dark umbra. The moon will be deepest in shadow and darkest at 2:59 a.m. If you’re only interested in waking for a few moments to catch a glimpse of the eclipse, this is the time to set your alarm for.
Totality ends at 3:41 a.m., when the moon begins to emerge from the umbral shadow into the partial sunlight of the penumbra, where only some of the sun’s light is blocked. If you’re a die-hard fan of lunar eclipses, you can stay up until the eclipse officially ends at 5:56 a.m. — but totality is the best part of the show, so when that’s over you can go back to bed and not worry about missing much.
Why doesn't the moon completely disappear at totality?
During a total lunar eclipse, the moon passes through Earth’s full shadow, the umbra, where no direct sunlight falls, yet it is still lit up in a dull orange or reddish light.
Sunlight that slips around the edges of the Earth is bent and filtered by our atmosphere, its twilight rays shining into the dark umbra like a dim night-light. We see the same rosy glow at dusk every evening as sunlight is scattered over the horizon to illuminate the landscape, even after the sun has set. The same atmospheric glow passes on into space, shedding its radiance into Earth’s shadow.
An astronaut standing on the moon and looking back at the Earth during a total lunar eclipse would see a black disk rimmed in a ring of fiery light that includes all the Earth’s sunrises and sunsets in one stunning view.
How often do lunar eclipses occur?
Lunar eclipses occur regularly, anywhere between two and four times per year. Some are partial eclipses, when the moon only grazes Earth’s umbral shadow. Some are penumbral eclipses, where the moon misses the umbra completely and only passes through Earth’s half-shadow, its light dimming so subtly it might not even be noticed.
A total lunar eclipse happens about every two and a half years, on average, and is only visible from half of our planet, and in some locations only partially. So, November’s full, end-to-end eclipse is a very rare treat for people on the West Coast who can enjoy it — and well worth getting up in the middle of the night to witness.
Benjamin Burress has been a staff astronomer at Chabot Space and Science Center since July 1999.
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