SAN FRANCISCO - Something special is happening in the sky Tuesday night, and in the early hours of Wednesday morning -- and "once in a blue moon" doesn't even begin to cover it.
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"Tonight we have a 'super blue blood moon,'" said Exploratorium staff teacher Lori Lambertson. "And none of those are real scientific terms."
But it is a scientific anomaly:
"That hasn't happened in something on the order of 150 or so years," said NASA lunar scientist Brian Day. "That's something that nobody alive has ever seen."
The long name explains a celestial coincidence, said Lambertson. First, the "supermoon:"
"We have a full moon that appears brighter because the moon's about 7 percent closer," she said.
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It's also the second full moon this month -- something that's historically been called a "blue moon." But don't expect the moon to appear blue. In fact, the third part of this unusual event will make it look unusually red:
"A total eclipse of the moon," Day said. "Where the moon is going to actually pass through the shadow of the earth."
Earth's atmosphere scatters the sunlight that passes through it, turning the moon the color of blood. That's where we get the "blood moon" part of "super blue blood moon." And though the name is a mouthful, it's an event everyone can learn from.
"It's one of the ways ancient astronomers had evidence that the shape of the earth was round," Lambertson said.
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Science has advanced since then, but NASA will still be gathering important data from this eclipse, using the Lunar Reconnaissance Orbiter that's currently in orbit around the moon. As the lunar surface darkens and rapidly cools off, the orbiter will take temperature readings. Measuring the rate at which different formations cool will give NASA important clues about which parts of the moon's surface are made of dust, ice or solid rock.
"And that's important as we start planning our return to the moon," Day said. "We really need to know the kind of real estate we're going to land on."
Until then, you can explore the moon's surface through NASA's Moon Trek website, or just by looking up.
"Sometimes, getting out in nature is hard for us in the city, but the sky is always available to us," Lambertson said.
The total lunar eclipse will be visible in the western sky before sunrise on Wednesday morning, with the greatest eclipse happening between 5 a.m. and 6 a.m. The moon will remain partially eclipsed as it sets over the western horizon.
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