May 12, 2003

Lunar Eclipse

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Sky watchers in North and South America will be favored for a copper-colored lunar eclipse on May 15/16, 2003.




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May 28, 2105: The airlock door slid sideways and Jack stepped out onto the moon.

The dusty ground was bright, reflecting light from the sun above. Squinting, Jack scanned the curved horizon. There: a smooth spot in the distance. "Perfect," he thought as he bounded toward it, bunny-hopping Apollo-style.


A view of the Moon captured during the Apollo 15 mission

"OK, Jack," the radio crackled after a while. "You better stop now and get ready. The eclipse starts in a few minutes."

"Dad... I know what I'm doing," he radioed back, his 14-year-old voice gruff. To prove it, he took one more hop--then stopped. Jack didn't want to miss anything.

Grunting, he reached behind his back--not so easy in a pressurized space suit--and tugged at some Velcro straps. A little fiddling and he had it: his great-grandfather's camping chair. Nearly 100 years old, made of green canvas and aluminum tubes, Jack's family treasured the old thing.

Jack pressed the chair into the moondust, maneuvered around and wriggled the bottom of his space suit between the narrow armrests. A button on his glove, pressed, sent an electrical current surging through his visor, which darkened like welding glasses. "I love these advanced materials," he grinned. Staring straight up at the sun, his eyes felt good.


lunar eclipse animation created by Francis Reddy
For the next hour he patiently waited, watching the sun's disk glide behind something big and dark: Earth. From the moon, Earth looked three and a half times wider than the sun. Sometimes Earth was amazingly bright, blue and cloudy-white. Today, though, the planet's night side was facing moonward.


Finally, the sun vanished. This is what he had been waiting for.... Lit from behind, Earth's atmosphere began to glow around the edges, ringing the dark planet with all the colors of a sunset. And from there sprung the Sun's corona: pale white, sticking out like Jack's sister's hair when she rubbed her stockinged feet on the carpet back in the lunar habitat.

Jack cleared his visor to enjoy the view.

The ground around him wasn't bright any more. It was dim and deep red--aglow with sunlight filtered through the edge of Earth's atmosphere. All at once every sunset on Earth was shining down on Jack.

"I bet he would love this," said Jack. He was thinking of his great-grandfather, Don Pettit, the science officer of the first International Space Station. Don had loved to watch sunsets and the red edge of Earth's atmosphere from orbit. When his tour of duty in space was done, he used to sit in this old chair by the campfire and tell his boys all about it, or so Jack's dad claimed.

The radio crackled again: "Jack, are you seeing this?"

"I sure am, dad, thanks." He completely forgot to be gruff.



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May 12, 2003: The astronomy in this story is real. The rest is science fiction--at least for now.


One day lunar colonists will stride outdoors to enjoy such eclipses. They happen about twice a year whenever Earth passes directly between the sun and moon. Our planet's shadow darkens the moon, while sunlight filtering through the edge of our atmosphere turns it red.

Right: Canadian photographer Dominic Cantin captured this image of the Moon inside Earth's shadow on January 20, 2000.

Here on Earth we call them lunar eclipses--and one is about to happen. On May 15th and 16th the moon will glide through Earth's shadow for the first time this year.




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The eclipse begins at 10:00 p.m. EDT (7:00 p.m. PDT) on Thursday evening, May 15th, or 0200 Universal Time (UT) on Friday morning, May 16th.

At first the moon will seem pale and bright, as usual. During the hour that follows, however, it will plunge into the darkest part of our planet's shadow--a region astronomers call "the umbra." Jack was inside the umbra when he saw the sunset-red ring around Earth. On May 15th the moon will be inside the umbra for about 52 minutes, from 11:14 p.m. to 12:06 a.m. EDT (8:14 to 9:06 p.m. PDT) or 0314 to 0406 UT on May 16th.

How dark and red the moon appears during that interval depends on what's floating in Earth's atmosphere. Dust storms and volcanic eruptions can fill the air with particles that redden sunsets and eclipsed moons alike. Sometimes the moon is so dark it's nearly invisible. Other times it's a lovely shade of bright copper.


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Above: May 15/16, 2003, lunar eclipse visibility map. [more]

Sky watchers in North America and South America are favored. Except for Alaska and some remote areas in Canada, the eclipse will be visible from all parts of those two continents. In Europe and Africa, the early stages of the eclipse will be visible for just a while before dawn on May 16th.

The eclipse will not be visible from Australia or most of Asia. Or from the Moon, but that's only because there's no one there to see it ... not yet.

Visit NASA's Eclipse Home Page for more information about this and other lunar eclipses.




Web Links

May 15/16 lunar eclipse links: from NASA; from Sky & Telescope; from Celestial Delights; from Jack Stargazer; from NPR's Science Friday;

Thanks to Francis Reddy for creating the animation, which appears in this story, of the sun moving behind the earth as viewed from the moon.

A Total Eclipse of the Sun ... on the Moon (Science@NASA)

Why isn't the moon totally dark when Earth gets between it and the sun? It's because of Earth's atmosphere. (continued below)



White light from the Sun is a mixture of all the colors of the rainbow. When a ray of "white" sunlight passes at grazing incidence through Earth's atmosphere, molecules and aerosols in the air scatter blue light in all directions (this is why the sky is blue). The remaining reddish light is bent (refracted) into Earth's umbral shadow zone, giving the eclipsed Moon a coppery glow. Copyright-free image credit: Tony Phillips.


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