The subtle event, known as a penumbral eclipse, can be observed by everyone on Earth’s nightside.
As the moon prepares to blot out the surface of our sun in two weeks, it’s warming up with a penumbral lunar eclipse on Sunday night or Monday morning, depending on your time zone.
In general, eclipses are the result of a delicate dance between the moon, the sun and the Earth. Lunar eclipses occur when the planet slides between the sun and the moon. That’s in contrast to a solar eclipse, which happens when the moon interjects between the other two bodies.
“It’s all about shadows,” said Noah Petro, a planetary geologist who works on the Lunar Reconnaissance Orbiter for NASA. The sun beams light on Earth, casting a long shadow behind it.
“And every once in a while, the moon wanders into that shadow,” Dr. Petro said.
In the most dramatic version of the event, the darkest part of Earth’s shadow washes over the lunar surface, making it shine crimson. This is a total lunar eclipse, also known as a blood moon.
But you won’t see that happen overnight. At 12:53 a.m. Eastern time on Monday, the moon will start to pass through only the outermost part of Earth’s shadow, known as the penumbra. As a result, its full face will slightly dim.
Is that worth trying to see? Dr. Petro thinks so. But the change will be difficult to catch with the naked eye, so he encourages using binoculars or a telescope, and taking note of how the moon’s brightness changes through the night.
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