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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