On the morning of December 10, the Moon will move through Earth’s shadow producing a total lunar eclipse. For observers in Utah, the Moon will set about the time of greatest eclipse. Sharp-eyed observers should detect the Moon entering into Earth’s umbral shadow at 5:46 a.m. Look for the Moon in the west, about 20 degrees above the horizon. Totality begins at 7:06 a.m. At this time the Moon will appear about 5 degrees above the horizon and could be hidden behind mountains from some observing locations. Moonset for a flat horizon is 7:44 a.m. For the longest view of the eclipse, find an observing location with a clear horizon in the west-northwest.
Meteor showers occur when Earth passes through a stream of debris given off by a comet. Particles that make up this debris stream typically range in size from pebbles to sand grains. As they enter Earth’s upper atmosphere at high speeds, they vaporize 50 miles above our heads, producing the slivers of light streaking across the sky that we call a meteor or “shooting star”.
Astronomers began searching for a comet as a source of the particles. Their search was unsuccessful until 1983, when NASA’s Infra-Red Astronomy Satellite (IRAS) spotted an object, several miles across, moving in about the same orbit as the Geminid debris stream. The object was named 3200 Phaethon. Oddly, Phaetheon seems more like an asteroid. It is rocky, not icy, and has no obvious tail. If Phaethon is an asteroid, how did it produce a stream of particles? Several possible explanations have been proposed. None are completely satisfactory. The mystery continues.
On a dark, moonless night, the Geminid meteor shower can produce as many as 120 meteors per hour for observers far away from city lights. However, this year the meteor shower occurs four days after the full moon. So, moonlight from a waning gibbous moon should greatly reduce the number of visible meteors. The shower peaks on December 14 at 11 a.m. MST, so observers in Utah should look on the nights of the 13th and 14th.