Night Lights: Newly dark skies lit by late-summer constellations

By Andy Veh, for the Redoubt Reporter

Graphic courtesy of Andy Veh

After a rainy summer we can hope for a warmer fall with clear skies as it gets darker earlier in the evening. The following describes the starry evening sky throughout September.

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 towards 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. Also high in the sky as well, almost in the Zenith, is Cygnus, The Swan, which also resembles 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. Beneath it is the first object you are able to see, ultrabright Jupiter. Turning to the west, we can see bright-red Arcturus setting, a sign that summer is over. 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’s Earth rotation that gives us this illusion). Thus, the evening western constellations set while, in the east, Taurus, Orion, Gemini and Cancer are rising throughout the night, telling us that winter is coming up.

According to information published in “Sky & Telescope” and “Astronomy” magazines and on the Internet, all planets should be visible this month. However, that is not the case for Alaska. Mercury, Saturn, the bright star Spica, Mars and Venus are all strung along a line that, as seen from more-southern latitudes, would be angled above the eastern horizon after sunset. In Alaska, that line of star and three planets are parallel to the horizon and therefore they all, unfortunately, slip beneath the eastern horizon during sunset.

That leaves a very bright Jupiter as the sole holdout among the bright planets, situated low in the southeast. It is easily the first object that pops into view after sunset. Aside from its moons, which can be seen with strong and stable binoculars, it also currently guides you to Uranus, which appears right above it. For binocular use, I recommend propping your elbows on a car’s roof for stability.

Neptune can be found to the lower right of these two, very low in south. Both of these outer gaseous planets can be found with those strong and stable binoculars and good sky charts, posted at http://media.skyandtelescope.com/documents/Uranus_Neptune_2010.pdf. By the way, Neptune is so far out (about 3 billion miles) that it would take a truck driver averaging 150,000 miles per year about 20,000 years to get there. Neptune, meanwhile, orbiting our sun at 12,000 mph without ever taking a break, makes its journey in just 165 years. And since it was discovered in 1846, due to a joint English/French/German effort, it will mark its first complete orbit since its discovery in July 2011.

In contrast, Mercury needs a mere three months to orbit our sun at 100,000 mph. While the speediest planet is in line with the sun on Sept. 3 — this is called inferior conjunction — just two weeks later Mercury reaches its greatest elongation and is nicely situated low in the east before the sun rises, between about Sept. 15 and 25.

The almost full moon joins Neptune on Sept. 19, making it easier to find the planet. The full Moon can be found right above Uranus and Jupiter on Sept. 22.

Andy Veh is a professor of astronomy and physics at Kenai Peninsula College’s Kenai River Campus. This column can be found the last Wednesday of every month in the Redoubt Reporter.

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