The bright summer stars Deneb, Altair, and Vega, which form the summer triangle (July 26 - August 1), still dominate the upper reaches of the sky this week. They will be with us at least two more months, though they trend a little more toward the west each night. It's still summer, but already a new crop of stars is rising in the east - the autumn sky - and by this time next month, they will reign supreme.
Most distinctive in this group is the Great Square of Pegasus, now nearly halfway up in the northeastern sky. It is indeed, a large squarish asterism, with a bright star marking each corner. You could place 26 full Moons from its eastern side to its western side. Since a full Moon is roughly half a degree in diameter, that means the Great Square is about 13 degrees wide.
The neck and head of the flying horse consist of a string of four stars stretching westward from the southwestern corner star, the brightest of the square's stars. The forelegs - two parallel strands of fainter stars -extend straight out from the square's northwestern star.
Appended to the square's northeastern corner star is another constellation: Andromeda the Maiden. Andromeda is still fairly low and not easy to make out, but by next month she will be easier to see. Incidentally, in this constellation lies the most distant object that can be seen with the unaided eye - the Andromeda Galaxy (November 1 - 7).
North and slightly east of the Great Square lies a distinctive zig-zag group of six stars shaped somewhat like an up-ended W. This is the constellation Cassiopeia the Queen. The grouping is supposed to depict the Queen's throne, which you can see this week if you stand on your head. The throne rises legs first. Cassiopeia lies in the Milky Way, so if you scan this constellation with binoculars you should have no trouble seeing many stars and a few star clusters. A beautiful 'double cluster' lies east of the northeasternmost star in Cassiopeia. Under a dark sky free of city light pollution, you can see this intriguing object without optical aid. It looks like a small cloudy patch of light, an enhancement of the Milky Way's glow. (See October 4 - 10.)
East of Cassiopeia, and still down among the trees, lies Perseus the Hero, a giraffe-shaped grouping of about 20 stars. (See, 'The rescue of Andromeda,' October 11-17.) This constellation is better placed around 11 o'clock this time of year. When you look in this direction of the sky, you are looking toward the outer disk of the Milky Way, exactly opposite from its center in Sagittarius.
It's still officially summer, and will be for another month. But the sky hints at the coming of autumn, of cooler days, and sometimes chilly nights. The seasons are indeed written in the stars.
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