Sacred monuments

For more than 1,500 years, countless Neolithic and Bronze Age peoples labored to build the mysterious stone structure known as Stonehenge. Why? What was its purpose? Legend once tied the structure to the Druids, but it was built far earlier than their era and there is no evidence they took any interest in it at all.

The first hint as to its purpose came around 1840, when a Rev. Edward Duke remarked that certain stones seemed to line up with the midsummer sunrise and midwinter sunset. Sir Norman Lockyer tried to establish the age of Stonehenge in 1901 by calculating when midsummer sunrise would have aligned with the structure’s major axis. His date of 2000 B.C. was off by centuries, but he reinforced the idea that Stonehenge was connected to lunar and solar events.

Amateur British astronomer C.A. Newham, working in the early 1960s, claimed to have found alignments showing the ancient builders were following an 18 year, 11 day repeating pattern of solar and lunar eclipses called the Saros cycle. In 1963, Gerald Hawkins used a computer to match lunar and solar events as they would have appeared to the ancient builders with various structural alignments at Stonehenge. His results, published in the 1965 book “Stonehenge Decoded,” were startling. It takes 56 years for the moon to complete one full eclipse cycle. Hawkins found that specific events, such as a total lunar eclipse, could be predicted years into the future using Stonehenge’s 56 Aubrey Holes as a “computer.”

Hawkins was able to match many events of importance to the ancients, such as solstices, equinoxes, and midsummer and midwinter points to alignments in the complex. Stonehenge, writes Hawkins, was a Stone Age computer that allowed the ancients to track significant solar and lunar events for many years into the future. Many do not agree with Hawkins, saying that such calculations would have been far beyond the builders’ capabilities. Yet the alignments seem to occur well beyond sheer coincidence and, given the hundreds of other “sacred monuments” found around the world, Hawkins’ hypothesis seems to be the most logical.

Focus on the planets

Mercury makes its best appearance of the year this month. Look for the elusive inner planet on the southeast horizon, to the lower left of Jupiter, about a half hour before sunrise.

Venus is brilliant in the southwest at dusk, where it is the brightest “star” in the sky all month. Be sure to check out Venus on the evening of Dec. 4 when the crescent moon stands to the planet’s immediate lower left.

Mars appears larger and brighter in early December than it will for another decade. Look for Mars high in the southeast at dusk, where it is recognizable for its reddish-orange color and the fact it is brighter than any star in the night sky. Be sure to see Mars early in the month, for the Red Planet will diminish in both size and brilliance as the days wear on.

Jupiter is high in the southeast about an hour before sunrise, where it will spend the month among the stars of Libra the Scales. Jupiter’s four major moons, Io, Callisto, Ganymede, and Europa will be visible to viewers with telescopes as they conduct an intricate dance around the gas giant.

Saturn rises in the east about 9 p.m. as December opens and by 7 p.m. at month’s end. The planet’s famed ring system still has a favorable opening and tilt for viewing the gaps between rings and is readily visible by moderately powerful telescopes. Saturn will edge nearer to the Beehive Cluster throughout the month.

Uranus and Neptune are situated in the constellations of Aquarius and Capricornus, respectively. Viewers with powerful binoculars should be able to spot them low in the southwest at nightfall after first checking out the much more visible Mars. The finder charts in the June issue of Sky & Telescope will help in the search.

Pluto is lost to view behind the sun during December.

December events

1 Sunrise, 6:52 a.m.; sunset, 3:56 p.m. New moon, 9:59 a.m.

4 Look for the crescent moon to the immediate lower left of Venus as darkness falls. The moon is at perigee, or its closest approach to the Earth, for the month.

7 Fomalhaut, the “autumn star,” shines in solitary splendor far below the moon during the early evening hours.

8 The moon is at first quarter, 4:36 a.m.

11 Look for Mars just to the lower left of the moon at dusk. As a point of interest, although they appear close, Mars is 245 times further away than the moon.

12 Look to the southeast about an hour before sunrise where, from left to right, Mercury, Jupiter, and the bright star Spica form an ascending line in the sky.

14 The Geminid meteor shower will peak tonight. However, the nearly full moon will mask all but the brightest meteors. Normally the shower is one of the most visible, but Guy Ottewell in his “Astronomical Calendar” predicts this year “will be absolutely dreadful.” If you are out between 10:00 p.m. and dawn, however, keep an eye out for a particularly bright specimen.

15 Full moon, 11:14 a.m. The full moon of December is called the Moon Before Yule or the Long Night Moon.

18 The sun enters Sagittarius on the ecliptic.

21 Winter solstice, 1:36 p.m. This marks the sun’s farthest journey south of the equator, leading to the shortest days and longest nights in the northern hemisphere. It’s all downhill from here to summer! The sun enters the astrological sign of Capricornus but, astronomically, has just entered Sagittarius. The moon is at apogee, or greatest distance from Earth today.

23 Moon in last quarter, 2:37 p.m.

25 Merry Christmas!

29 Look to the southeast horizon about an hour before sunrise. Mercury is low on the horizon with a thin, waning crescent moon to its immediate right. The red star Antares is to the moon’s upper right.

31 New moon, 10:11 p.m. This is the second new moon this month. Sunrise, 7:13 a.m.; sunset, 4:04 p.m.

Clair Wood taught physics and chemistry for more than a decade at Eastern Maine Technical College in Bangor.