by Kim Malville
What’s in the sky this month?
January 2: Look for the thin crescent moon to the upper left of Venus some 45 minutes after sunset.
January 3: A short but sweet Quadrantid meteor shower, lasting for a few hours just before dawn.
January 5: Jupiter is in opposition to the sun in the constellation of Gemini, rapidly moving retrograde. It rises at sunset and sets at sunrise. The King of the Planets is truly bright.
January 14: Look for Jupiter just to the left of the full moon in Gemini
January 31: The very thin crescent moon will be close to Mercury at dusk low in the west-southwest.
Comet Ison has died
Comet Ison has not become the great and wonderful comet we had hope for. Through no particular fault of its own, it was dismembered as it passed through the fire of the sun’s corona on November 28. Not only did it get within 700,000 miles of the sun’s surface, but it traversed the magnetic fields and streams of million-degree hot electrons and protons of the corona.
Halley’s Comet and the Black Death
The ancient world viewed the heavens as an eternal realm where change could not occur. When comets occasionally appeared they were often regarded as harbingers of doom. A recent study suggests at in A.D. 536 a piece of Halley’s comet broke away from the nucleus and slammed into the earth’s atmosphere, producing so much dust that our planet suffered a major cooling, which may have been linked to world-wide drought and famine around the world. It is also speculated this climate change may have made the world susceptible to “Justinian’s plague” in A.D. 541-542, which was the first recorded emergence of the Black Death in Europe.
These results come from ice cores from Greenland that reveal between A.D. 533 and 540 the presence of large amounts of atmospheric dust, not all of it coming from Earth. At the meeting of the American Geophysical Union in San Francisco last month, the presence of “alien” dust in these ice cores was announced. Certain characteristics, such as high levels of tin, identify a comet as the origin of the alien dust. It was deposited during the Northern Hemisphere spring, suggesting that it came from the Eta Aquarid meteor shower, produced by material shed by Halley’s comet, which Earth plows through every April-May. But the dust of a typical meteor shower cannot explain the global cooling event of 536-537, during which the planet may have cooled by as much as 5.4° Fahrenheit. As you know, Halley’s Comet passes Earth every 76 years. It appeared in our skies in A.D. 530 and was unusually bright.
The nuclei of comets are typically covered with a layer of dark tar. A few holes in this dark layer allow sunlight to strike ice underneath and produce, by sublimation, jets of gas and dust. The photograph of Comet Hartley taken by the Deep Impact Space Craft shows a dark, irregular object with jets of gas. Hartley is only 1.2 miles long, while the nucleus of Halley’s comet is some 9 miles long. These dirty ice balls are fragile objects, and it is easy to imagine a fragment breaking off. It is speculated that such a portion broke off, exposing fresh ice and producing a brighter comet. It’s unclear where exactly this comet chunk may have hit Earth. A comet fragment just 2,000 feet wide could have caused the 536-537 cooling event if it exploded in the atmosphere and its dust was spread evenly around the globe.
Not all appearances of Halley’s Comet were considered dangerous and evil. A considerably more benign view of the comet is found in the painting by Giotto, “The Adoration of the Magi”, where Giotto appears to have fashioned the Christmas star after the brilliant appearance of Halley’s Comet in A.D. 1305.
Machu Picchu’s Sacred Sisters
I’m delighted to report that the archaeologist Gary Ziegler and I have just published a book on the archaeology and astronomy of the Inca world: Machu Picchu’s Sacred Sisters: Choquequirao and Llactapata—Astronomy, Symbolism, and Sacred Geography in the Inca Heartland. We describe it as a combination of extreme archaeology and deep astronomy. The “deep” astronomy means that we try to relate astronomy to the intricacies and complexities of Inca culture. The book describes the exploration of a number of previously unknown Inca sites, including the sun temple at Llactapata, which we located in 2003 in the cloud forest overlooking Machu Picchu.
The son of Pachacuti, the founder of the Inca Empire and the builder of Machu Picchu, wishing to outdo his father, built his own version of Machu Picchu at Choquequirao at a similarly dramatic location, overlooking the deep canyon of the Apurimac River. For the Inca it would have been a 7-10 day walk westward from Machu Picchu to reach Choquequirao. Today, it can also be reached in two days by descending 5000 feet into the Apurimac River and then climbing back up again. The walk from Choquequirao to Machu Picchu has recently been described in the lively book Turn Right at Machu Picchu by Mark Adams. Just this year the Peruvian government announced plans for a 5km aerial tramway to span the Apurimac gorge, and Choquequirao may become another major destination for visitors to Peru.