On Dec. 21, for the first time in almost three years, a total lunar eclipse of the moon will take place for viewers in most parts of North America. A lunar eclipse can occur only at the full moon and then only if the moon passes through some part of the Earth’s shadow. The latter is divided into two parts, an outer penumbra and an inner umbra portion. A total eclipse, when the sun’s rays are totally blocked from the moon, occurs when the moon passes through the umbra as it will on Dec. 21. Also, since the eclipse occurs only 18 hours before the winter solstice, the moon will be high in the sky. The times for various parts of the eclipse are: partial begins at 1:33 a.m.; totality begins at 2:41 a.m.; totality ends at 3:53 a.m. and eclipse is over at 5:01 a.m. At totality the moon will be a beautiful bronze or orange-red color. Pray for a clear sky.
Focus on the Planets
Mercury is very low in the southwest a half-hour after sunset on Dec. 1. It disappears from view about mid-month but reappears in the southeast just before sunrise at month’s end.
Venus blazes in the southeast morning sky rising four hours before the sun where it is 25 times brighter than the brightest star Sirius. On Dec. 2, Venus is joined nearly side-by-side with the crescent moon, with Saturn high above them.
Mars is very low in the southwest after sunset and clear skies and binoculars will be needed to spot the far distant red planet. At dusk on Dec. 13 Mercury and Mars are less than a degree apart on the southwest horizon.
Jupiter dominates the southern horizon as night falls. The giant planet comes into view less than 30 minutes after sunset and remains in view until well after midnight. The four moons of Jupiter will put on a lively display as they orbit the planet.
Saturn rises in the east about two hours after midnight but is best observed high in the southeast at dawn. The rings of Saturn are finally beginning to open up and will have a tilt of nearly 10 degrees at month’s end.
Uranus is best found by zeroing in on Jupiter and finding the elusive blue-green planet just to the east within the same binocular field. By month’s end Jupiter will have drawn within a half degree of its distant companion in preparation of passing it.
Neptune is high in the southwest nestled among the stars of Capricornus, visible by telescope as a tiny blue-gray disk.
1: Sunrise, 6:52 a.m.; sunset, 3:56 p.m.
2: Check out the southeast horizon at dawn where Venus and the crescent moon are nearly side-by-side with Spica to the upper right and Saturn situated well above the trio.
5: New moon, 12:36 p.m.
7: Mercury, Mars and the moon are grouped within a tight circle in the early pre-dawn sky.
13: This is St. Lucy’s Day, once considered to be the middle of winter. The moon is at apogee or farthest distance from Earth. The moon is in first quarter, 8:58 a.m.
14: The Geminid meteor shower peaks tonight and, with the moon setting around midnight, viewing conditions should be ideal if the weather cooperates. At its peak, about 2:00 a.m., this stream could produce 100 to 120 meteors per hour from the vicinity of Castor in the constellation of the Twins.
18: Sun enters Sagittarius on the ecliptic.
21: Full moon, 3:14 a.m. The full moon of December is known as the Long Night Moon, Moon Before Yule and the Cold Moon. Winter solstice, 6:42 p.m. The sun is at its southernmost point below the celestial equator, making this the first day of winter in the Northern Hemisphere. The sun at the solstice enters the astrological sign of Capricornus but astronomically has just entered Sagittarius. Total eclipse of the moon tonight.
25: Merry Christmas! The moon is at perigee or closest approach to the Earth.
28: Moon in last quarter, 11:19 p.m.
31: Sunrise, 7:13 a.m.; sunset, 4:04 p.m.