Heavens offer unique clues to the seasons
By ROD KENNEDY
Special to the Star-Tribune
Before the advent of calendars, the only way to mark the changing of the seasons was through direct observation. Ancient peoples observed the passage of the sun north from the Winter Solstice, and then south from the Summer Solstice. In Mesoamerica the people observed the sun passing directly overhead twice a year by using special tubes in the temples that pointed at the zenith.
For people north of the Tropic of Cancer (23.5 degrees N) this method was not an option because the sun never passes directly overhead at those latitudes. Therefore, people in Europe and North America had to rely on other observations to mark the change of seasons. One method of observing the sun’s changing seasonal position is with a structure such as Stonehenge in England or the famed Serpent of the Sun in Ohio. Ancient monuments such as these were aligned with the sunrise on certain days of the year, typically the Summer Solstice. Some archaeologists suggest that the Big Horn Medicine Wheel in northern Wyoming is such an observatory.
However, in some situations such a structure is not practical. Fortunately there are seasonal markers in the night sky that are just as easy to use. For example, if we step outside on a clear night and look north, we find the Big Dipper. In May the Big Dipper is turned upside down, as if to dump its contents to earth in the form of life giving spring rain. To ancient agricultural peoples this would have been a good sign for the beginning of the growing season.
Another constellation associated with agriculture is the constellation Virgo, the Maiden. We can find Virgo by using the Big Dipper as a guide. Using the dipper’s curved handle we “follow the arc to Arcturus,” and then “speed on to Spica.” Spica is the brightest star in Virgo and is almost due south throughout May.
Virgo has been associated with agriculture for thousands of years, and is often depicted as a young woman holding a sheaf of wheat or grain in her hand. In ancient Egypt she represented Isis; in Greece she was Persephone, daughter of Ceres goddess of the harvest. In Babylon she was Ishtar, queen of the stars and to ancient Christians she was the Madonna or Ruth of the Fields.
Although Spica is the only bright star in Virgo, the area of this constellation is far from empty. Where Virgo borders Coma Berenices (due north of Virgo) is an area known as the Coma-Virgo galaxy field. Photographs taken from large Earth-based telescopes reveal more than 3,000 galaxies. More than 100 of these are visible with medium to large backyard telescopes. In most small telescopes the galaxies will appear only as faint smudges of light.
Yet knowing that each smudge is a vast stellar city thousands of light years across makes the view staggering. As Thomas Carlyle once wrote:
“Sis (sic) it not reckoned still a merit, proof of what we call a ‘poetic nature,’ that we recognize how every object has a divine beauty in it; how every object still is ‘window through which we may look into Infinitude itself?'”
Observers looking 15 degrees east of Spica will notice another bright object in the night sky. This is the planet Jupiter. Jupiter is the only planet visible throughout the night in May. Mars and Saturn vanish not long after sunset and Venus does not appear until just before dawn, so Jupiter glides silently along between Virgo and Libra the Scales, a lonely light in the southern sky.
Rod Kennedy is an employee at the Casper Planetarium.