Sky at a Glance September 14 – 21

Photo showing location of two "crown" constellations, Coroan Borealis in the high western sky and Corona Australis in the low southern night sky.

This Week’s Sky at a Glance, 2019 September 14 – 21
~by Curt Nason

Two stellar crowns are included among the 88 official constellations. Both are above our horizon around 8 pm but one requires an unobstructed and near-pristine sky to the south. Both crowns arise from mythological tales of the popular demigod Dionysus (Bacchus in Roman mythology), the god of wine.

Corona Borealis, the Northern Crown, is a pretty semicircle of stars situated high in the west, one third of the way from Arcturus to Vega. In mythology, Ariadne was the daughter of King Minos of Crete. She helped Theseus slay the bull-headed Minotaur and escape from the Labyrinth, and then accompanied him and his crew on a voyage home to Athens where they were to wed. Along the way they stopped at the island home of Dionysus, who was a great and wily host. After a night of revelry Theseus was forced into leaving without Ariadne, and Dionysus presented her with a beautiful crown if she would be his bride. The crown was placed in the sky to commemorate their wedding.

The Sagittarius teapot asterism is low in the south at 9 pm this week, and Corona Australis, the Southern Crown, rides the horizon below. This semicircle of stars is sometimes called the lemon wedge asterism, to go with the teapot and the teaspoon above the teapot’s handle. Dionysus was the result of an affair between Zeus and a mortal woman. The gods had to be careful in such affairs as mortals could not withstand the full passionate heat of their embrace. Vengeful Hera, the wife of Zeus, tricked the now-pregnant woman into requesting Zeus hold her as he would a goddess, and as expected she did not survive. The unborn child was sewn into the thigh of Zeus and raised by his aunt after birth. Later, Dionysus honoured his mother by placing a wreath in the sky. Such a start in life would drive anyone to drink.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:55 am and sunset will occur at 7:33 pm, giving 12 hours, 38 minutes of daylight (7:01 am and 7:37 pm in Saint John). Next Saturday the Sun will rise at 7:04 am and set at 7:19 pm, giving 12 hours, 15 minutes of daylight (7:09 am and 7:24 pm in Saint John).

The Harvest Moon, which is the full Moon nearest the autumn equinox, occurs at 1:33 am this Saturday so it will rise closest to full on Friday evening. Due to the shallow angle of the ecliptic at sunset this time of year, successive moonrises occur only 20-30 minutes later, making it seem like we have a full Moon several days in a row. Jupiter sets around 11 pm this week, followed by Saturn two hours later. Saturn is stationary on Wednesday, resuming its normal eastward motion relative to the stars. Telescope users might see Jupiter’s Red Spot between 9 and 10 pm on Thursday. Mercury, Venus and Mars are too close to the Sun for observing.

The Saint John Astronomy Club meets in the Rockwood Park Interpretation Centre this Saturday, and RASC NB meets in the UNB Fredericton Forestry-Earth Sciences building at 1 pm on September 21. All are welcome.

Questions? Contact Curt Nason.

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