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This Week’s Sky at a Glance, 2019 September 14 – September 21

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 at nasonc@nbnet.nb.ca.

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This Week’s Sky at a Glance, 2019 September 7 – September 14

The constellation Capricornus is a large chevron shape that is due south around 10 pm this week. A pair of stars marks each upper corner, and both stars of the western pair are colourful wide double stars. The sea goat arises from a tale of the Olympian gods being surprised by Typhon, the most ferocious of the rival Titans. Knowing Typhon was not fond of water, the gods changed into fish and escaped to the sea. The god Pan, who was half-goat and half-man, panicked and dove in before the transformation was complete and wound up with a goat’s head and the tail of a fish.

There are four common targets for backyard telescope users near Capricornus, but only the globular cluster M30 off the east side of the chevron is officially within its borders. It is also the easiest of the targets for binoculars. The globular cluster M75 lies west of the chevron in Sagittarius, while globular cluster M72 and the four-star (literally four stars, it is not an observing highlight) asterism M73 are above in Aquarius. Nearby is the more challenging, but worth the effort, Saturn Nebula, the gaseous remnant of a dead star that somewhat resembles the ringed planet.

A few millennia ago the Sun was in Capricornus at the winter solstice, when at midday it was overhead at its most southerly point, at latitude -23.5 degrees. This is the southern border of the tropics, and it is still called the Tropic of Capricorn despite the Sun now being in Sagittarius at this time. Earth’s 25,800 year polar wobble, called the precession of the equinox, is responsible for this shift.

This Week in the Solar System

Saturday’s sunrise in Moncton is at 6:46 am and sunset will occur at 7:46 pm, giving 13 hours of daylight (6:52 am and 7:50 pm in Saint John). Next Saturday the Sun will rise at 6:55 am and set at 7:33 pm, giving 12 hours, 38 minutes of daylight (7:01 am and 7:37 pm in Saint John).

The Moon is in a waxing gibbous phase this weekend and it is full, the Harvest Moon, on September 14. Jupiter and Saturn share the evening spotlight with it in the constellations Ophiuchus and Sagittarius, respectively. Telescope users might see Jupiter’s Red Spot around 8:15 pm on Thursday.

The Saint John Astronomy Club meets in the Rockwood Park Interpretation Centre on September 7, possibly moving to September 14 if Dorian dumps a lot of rain on this Saturday.

Questions? Contact Curt Nason at nasonc@nbnet.nb.ca.

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