This Week’s Sky at a Glance, 2019 September 21 – 28
~by Curt Nason
Autumn has arrived, and dedicated stargazers are happy to have the longer observing time afforded by earlier sunsets. The summer constellations appear reluctant to move on, however; emerging from twilight in nearly the same place each night because the earlier darkness masks that they rise four minutes sooner each day. But move on they do, and by mid-evening the two groups of autumn constellations lord over us.
Perseus sits below W-shaped Cassiopeia in the northeast these evenings. Cepheus, the king of ancient Ethiopia, is a house-shaped constellation fenced within his wife Cassiopeia, Cygnus and the North Star. The feet of Princess Andromeda are below the W of Cassiopeia, and her head is at the tail end of Pegasus the winged horse. The asterism called the Great Square of Pegasus rises as a large diamond, a harbinger of the baseball post season. Rounding out the mythological tale is Cetus, playing the role of a ferocious sea monster that is stoned, in a manner of speaking, by Perseus in his rescue of Andromeda. Cetus is actually a whale, and segues to the second group: the water constellations.
To the left of the Sagittarius Teapot we see the large chevron of Capricornus the sea goat, representing the goat-boy flautist Pan who didn’t completely morph into a fish when he tried to escape monstrous Typhon. Above and left is the source of all this water; Aquarius, the water bearing servant of the Olympians. Below him is the southern fish, Piscis Austrinus, and further east we have Aphrodite and Eros as Pisces the fishes. Cetus swims below them, and well above Capricornus we see Delphinus the dolphin trying to leap back into summer.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:04 am and sunset will occur at 7:19 pm, giving 12 hours, 15 minutes of daylight (7:09 am and 7:24 pm in Saint John). Next Saturday the Sun will rise at 7:13 am and set at 7:05 pm, giving 11 hours, 52 minutes of daylight (7:18 am and 7:10 pm in Saint John). The Sun crosses the equator Monday at 4:50 am – the autumnal equinox – heading south for winter.
The Moon is at third quarter this Saturday, and it is new and at perigee next Saturday. Jupiter and Saturn remain as the favourite targets in the early evening, but after twilight Jupiter is getting too low for steady atmospheric observing. Venus can be seen with difficulty in binoculars very low in the west 15 minutes after sunset, with Mercury a binocular field to its left.
The provincial astronomy club, RASC NB, meets in the UNB Fredericton Forestry-Earth Sciences building at 1 pm on September 21. All are welcome.
Questions? Contact Curt Nason.