Guest column: The importance of being Sirius: astonomy helped early people survive, foretold coming of seasons

Sirius, in the constellation Canis Major, is the brightest star in Earth’s night sky, and is about twice as bright as Canopus, the next brightest star.

The name Sirius comes from Ancient Greek, meaning glowing. However, what the naked eye perceives as a single star is actually a binary star system, consisting of a very bright main-sequence star and a smaller faint white dwarf companion (the size of the Earth, but with the mass of the sun) that travels in an elliptical orbit which separates them from between 8 and 32 Earth distances from each other. That’s about the distance Saturn is from the sun out to that of Neptune’s orbit. Sirius appears bright in the sky because it actually is very bright, but also because it is very close to us, being only 8.6 light-years away. Sirius is colloquially known as the Dog Star, because it is the most prominent star in the constellation Canis Major, the large dog.

The astronomy of all early peoples had to do with their survival. If you were dependant on knowing when certain animals migrated, when the weather was best to plant or harvest crops, how and when it was best to travel by ship, and know when and where certain sea animals and fish were abundant, you needed a clock. And the original clock for everyone on Earth, was the turning Earth. To these early cultures, the rotation of the sky above them, changing night to night and season to season became their time piece. In order to survive, one became familiar with the patterns of stars in the sky, to which, over the millennia, stories were made and orally passed on to each generation as a way to remember how the sky interacted with life down on Earth. Besides the sun and moon, other astronomical objects, such as certain constellations, planets, and bright stars, were often utilized by early cultures around the globe to mark special events. And Sirius being the most prominent star was no exception.

In ancient Egypt, Sirius is recorded in the earliest astronomical records and was known as the goddess Sopdet on which they based their calendar. The time of year that Sirius was first became visible in the sky just before sunrise (known as heliacal rise, when it had moved far enough away from the sun to be observed) was very important, as it marked the time just before the annual flooding of the Nile River and the summer solstice. After a 70-day absence from the skies (the passing of Sopdet through the underworld), the reappearance of Sirius once again provided for the marking of the fertile growing season. Although Egypt is one of the oldest cultures on Earth (about 8,000 years old), before 10,000 B.C., the star was not visible from the Nile Delta due to Earth’s 26,000 year precession (the top-like wobble of the Earth on its axis which changes the view of the sky over time.) Right now, Sirius is at about its highest point in the sky each year and is viewed at almost 40 degrees above the horizon in northern Arizona.

To the ancient Greeks, and later Romans, the appearance of Sirius foretold the coming of the hot and dry summer which caused plants to wilt, weakened men, and caused women to become aroused. Those suffering its effects were said to be star-struck sometimes with a burning sensation. This season following the star’s heliacal rising came to be known as the Dog Days of Summer. The Romans celebrated the heliacal setting of Sirius around April 25, where they would sacrifice a dog, along with incense and wine, so that the star’s emanations would not cause the wheat crops to fail.

In Chinese astronomy, the star is known as the Celestial Wolf. Many of the indigenous peoples of North America also associated Sirius with canines; the the Tohono O’odham of the American southwest note the star as a dog that follows mountain sheep. The Cherokee paired Sirius with the star Antares as a dog-star guardian at either end of the Path of Souls, and the Pawnee of Nebraska knew it as the Wolf Star or Coyote Star.

Though many cultures have associated Sirius with canines, not so the Aboriginal Australians. To them, stars and planets often represent ancestral heroes, creator beings, and sometimes inanimate objects. The Boorong People of Victoria considered Sirius and the star Rigel (in Orion) as two Wedge-tailed Eagles in the sky. Both birds soar high during the evening Australian skies. Sirius is also considered to be one of the spirit elders, one the first beings to inhabit the Earth.

For the Polynesians in the Southern Hemisphere, the star marked the beginning of their winter and was an important reference for navigating between the many sparsely separated islands around the Pacific. Along the horizon, stars acted as directional locators that assisted mariners in charting courses to particular destinations, and acted as latitude markers. For instance the celestial declination of Sirius is at the same latitude as the Fiji islands, and thus passes directly over the islands each night making its location possible to mariners.

Barry Malpus Northern Arizona Astronomy