On December 10, starting from about 9:45 p.m. the moon will slowly enter a full eclipse, reaching a total eclipse by around 11:05 p.m., and slowly ending at about 1:10 a.m. on Dec. 11.
Bigsen, a telescope manufacturer, will be supplying telescopes for moon viewing at Odaiba Marine Shore Park in Tokyo (in front of the Statue of Liberty). As an added attraction, Assistant Professor Akata Hidehiko, of the Japanese National Observatory, will explain what you are seeing.
A lunar eclipse takes place when the moon passes behind the Earth so that the shadow of the Earth stops the sun’s light from striking the moon. This can occur only when the sun, Earth and moon are lined up in a straight line; a lunar eclipse can only occur during a full moon when the moon is on the opposite side of the Earth, with the Earth between it and the sun.
A lunar eclipse lasts for several hours due to the large size of the Earth relative to the moon. A solar eclipse only lasts a few minutes at any given place, due to the smaller size of the moon’s shadow blocking the sun when seen from the Earth. Unlike a solar eclipse, which can only be seen in limited parts of the earth, a lunar eclipse can be seen from the entire side of the earth facing the moon.
When the sun, Earth and moon are lined up they are in what astronomers call “syzygy,” which is no doubt the best Scrabble word in the English language, but comes from the Greek word meaning “yoked together” in the sense that oxen are. It describes a straight-line configuration of three celestial bodies. Both solar and lunar eclipses may occur during syzygy, but at no other times.
Syzygy occurs every new moon. The reason that eclipses of the moon do not occur every new moon is because the plane of the moon’s orbit around the earth is somewhat titled relative to the earth’s equator. The moon’s orbit around the earth is roughly at an inclination of around 5.9%. So even though the Earth and the moon may be lined up in a straight line from the sun, the moon is usually too far north or too far south of the Earth’s shadow to be eclipsed by the Earth.
Eclipses occur only rarely when the orbit of the moon puts it in a position relative to the sun at full moon when it is straight behind the Earth; these positions on the Earth’s orbit are called the “lunar orbital nodes.” That’s when a lunar eclipse occurs.
“With luck, if the weather is clear, we’ll be able to see a red corona around the moon as the eclipse takes place,” the Japan National Observatory said.
For those who don’t want to spend a chilly December night outside watching the moon, the Akashi Observatory will have live streaming of it at http://www.ustream.tv/channel/astro135ch