Night Lights: Sky in September

Graphic courtesy of Andy Veh

Graphic courtesy of Andy Veh

By Andy Veh, for the Redoubt Reporter

During late evenings last month, some prominent bright stars, such as Arcturus, Vega, Deneb and Altair, were already visible. As it gets darker earlier in the evening this month, I hope to have clear skies.

First, find the Big Dipper low in the northwest, then take the distance between the dipper’s last two stars and extend it five times toward the zenith (the point straight up) and you get to Polaris, the North Star, which is a semibright star at the end of the Little Dipper’s handle. It also marks our latitude on the Kenai Peninsula at 60 degrees above the northern horizon.

Next, find the constellation Cassiopeia, in the shape of a W, on the other side of the Little Dipper, high in the northeast. High in the sky, as well, almost in the zenith, is Cygnus, the swan — it also looks like a cross. Its brightest star, Deneb, connects with two other bright stars, Vega and Altair, in the constellations Lyra, the harp, and Aquila, the eagle. Together they make up the prominent summer triangle.

Just left of them is the great square of Pegasus, high in the southeast. Turning to the west we can see bright red Arcturus setting, a sign that summer is over. It can also be found by following the handle of the Big Dipper’s arc. And rising in the northeast is bright yellow Capella, a corner of Auriga’s pentagon.

Throughout the night, all constellations move from east to west (of course it is Earth rotating that gives us this illusion) and thus the evening western constellations set while in the eastern sky Taurus, Orion, Gemini and Cancer are rising throughout the night, telling us that winter is coming up.

In the evening, Mercury, Venus and Saturn would be visible if Alaska were really located west of California, as many maps suggest. But since Alaska is so far north, all three appear too low on the western horizon, so that they set around the same time the sun sets.

Best situated in the evening sky this month are Uranus and Neptune. The best way of finding them is using a finder chart (e.g., in the February issue of Sky & Telescope — Then star hop with stable binoculars — I recommend propping your elbows on a car’s roof.

Uranus can be easily spotted. From Pegasus’ great square move south to Pisces’ circlet, then, with binoculars, look to the lower left until you find a bluish object that doesn’t twinkle. This month it is also quite close to the orange star Delta Pisci, which, at 300 light years, appears to be a somewhat brighter than Uranus at 0.0003 ly (2.5 light hours, or 1.7 billion miles). The full moon is near Uranus on Sept. 19. Neptune stays just to the right of the white star Sigma Aquarii, also appearing somewhat brighter than the planet. The full moon is near Neptune on Sept. 16 and 17.

Jupiter rises in the east late in the evening. Due to its glaring brightness, you cannot miss it. Jupiter will be visible during the evening all winter long. The third quarter moon joins the giant planet Sept. 27.

Mars follows Jupiter, rising way after midnight, joined by the crescent moon on the morning of Sept. 1 and again Sept. 30.

Andy Veh is an associate professor of physics, math and astronomy at Kenai Peninsula College.


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