Author: Matthew Cappucci / Source: Science News for Students
On the evening of January 20 to 21, the entire Western Hemisphere will be treated to a more-than-hour-long sky show: a total eclipse of the moon.
And the eruption of a volcano half a world away could make this particular event especially colorful — as in deep red.Total lunar eclipses aren’t rare. They happen somewhere across the globe once a year or so. But not everybody can see them. People have to be on the night side of Earth to catch the dark shadow fall over the moon’s face.
A lunar eclipse occurs when Earth moves between the sun and a full moon. At first, the moon appears to darken a bit as the shadow cast by Earth sweeps across the lunar surface. At what’s known as totality, Earth blocks out most moon-bound sunlight. This casts the darkest shadow. With only a fraction of the light passing through Earth’s razor-thin atmosphere, the moon plunges into sudden darkness.
But it doesn’t vanish entirely. That blanket of shadow, known as an umbra, lights up the moon enough that it remains slightly visible. It also turns the moon red. The reason has to do with optical physics. Most of the sunlight passing through our atmosphere will be scattered. Only the long-wavelength radiation — red light — penetrates. (It’s the same reason why sunsets appear red, orange and maroon.)
The moon rises Sunday (around 5:30 p.m. along the Atlantic coast, reaching its maximum eclipse near midnight for the Eastern Seaboard). Times will vary elsewhere, so be sure to check local information. Throughout North America, the moon will be high in the sky during the eclipse. That, plus a generally dry and clear night sky in winter, could make this the best viewing opportunity in years.
You might call this eclipse Big Red
This eclipse also will be supersized. That’s due to what some are calling a supermoon. That, too, is due to physics. The moon appears larger because it has been getting closer to Earth. At 357,342 kilometers (222,042 miles) away, it’s approaching its perigee — that point in its orbit when the moon will be nearest our planet. (If you’re looking for a super supermoon, you’ll have to wait until November 25, 2034. That’s when the moon will reach its closest in more than 85 years, according to TimeandDate.com.)
The January total lunar eclipse will be special for another reason:…
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