By Andy Veh, for the Redoubt Reporter
Compared to September, the sky in October shifts somewhat toward the east, with Bootes setting in the northeast. Its brightest star, Arcturus, can be seen in the early evening on the northeastern horizon. Prominent constellations and stars are the Big Dipper low and the Little Dipper (part of Ursa Major) high in the north, Cygnus with Deneb, Lyra with Vega and Aquila with Altair still high in the west.
These three stars form the summer triangle. It’s perhaps comforting that, in Alaska, we can see this summer triangle all winter along, albeit on the horizon. Cassiopeia appears overhead, near the zenith, with Pegasus’ square/diamond high in the south. Late in the evening Orion rises with Betelgeuse and Rigel in the east, following Taurus with Aldebaran and the Pleiades star cluster.
Neither Mercury, Venus, Saturn nor Mars are visible because they are rising and setting at about the same time as the sun, so this seems to be a terrible month for trying to view planets.
Jupiter rises at 3 a.m. Due to its glaring brightness, you can’t miss it in the predawn sky, looking southeast. It appears somewhat halfway between the bright stars Regulus in Leo and Castor and Pollux in Gemini. The third-quarter moon joins the giant planet Oct. 17.
Best situated this month are Uranus and Neptune. The best way of finding them is using a finder chart (e.g., at skypub.com/urnep. Among the many interactive sky charts that can be viewed online, try http://astronomy.com/observing/stardome, which belongs to Astronomy magazine), then to star hop with stable binoculars (I recommend propping your elbows on a car’s roof).
Uranus, especially, can be easily spotted — from Pegasus’ Great Square move south to Pisces’ circlet, then, with binoculars, to the lower left until you find a bluish object that doesn’t twinkle, making a triangle with delta and epsilon Pisci, which appear a little brighter than Uranus. Neptune is near sigma Aquarii. The almost-full moon joins Neptune on Oct. 4 and Uranus on Oct. 7 (in fact, around 11 p.m. Uranus and the moon are very close to each other). But the moon’s overwhelming brightness may make it harder to find either planet.
The great events this month are a total lunar eclipse Oct. 7 and 8 and a partial solar eclipse Oct. 23.
Lunar and solar eclipses always appear as pairs two weeks apart (once in a blue moon — pun intended — another eclipse joins them yet another two weeks later) with a frequency of almost half a year. That is because the moon’s orbit is lightly tilted. During one orbit (a little less than a month), as it crosses the plane of the Earth’s orbit twice (these are called the nodes), it does so in line with Earth and the sun (during the full moon, it’s a lunar eclipse, and with a new moon a solar eclipse) every half year.
A lunar eclipse can be observed from half of Earth. Everybody who is on the night side of Earth can view it. A solar eclipse can only be viewed by smaller regions on the day side of Earth, since the moon and its shadow are small (compared to Earth and its shadow, when it obscures the moon), and then the umbral shadow which produces a total eclipse covers an even smaller swath across Earth.
It is rare that a particular region experiences two consecutive eclipses, but this month almost all of North America is that lucky region.
If you stayed up late Oct. 7, past midnight into Oct. 8, you can imagine the moon entering Earth’s penumbral shadow at around 12:15 a.m. That part of the shadow is so faint that the moon hardly gets any darker and you can only “imagine” it. But around 1:15 a.m. the moon enters Earth’s umbral shadow and that can clearly be seen. The moon would then be veiled in total darkness from 2:30 a.m. until 3:30 a.m., except that sunlight is refracted through Earth’s atmosphere and gives the moon a reddish hue.
You can also see the curved shadow that the Earth projects onto the moon, which led Greek philosophers (among them Anaxagoras and Aristotle) to the conclusion that Earth is a sphere. Hence the belief that Earth may be flat had been buried around 500 B.C.
You don’t need a telescope to observe a lunar eclipse, so please excuse that I stay home late that night. Perhaps I’ll be waking up my son to observe with me. But I am planning to be at Soldotna Creek Park on Oct. 23 in the late morning, weather permitting. At quite precisely 11:51 a.m. the moon will start eating away at the sun.
At around 1 p.m. the partial eclipse will reach its maximum, at about 60 percent from Alaska. The top value for this partial eclipse is 80 percent, which can be observed from Prince of Wales Island in Canada’s Nunavut Territory (not Prince of Wales Island in Southeast Alaska) but traveling for those extra 20 percent is not advised. The eclipse should be over by 2:27 p.m.
You would need eclipse glasses to safely view the eclipse, but without binoculars or a telescope — do not use eclipse glasses with binoculars as you may damage your eyes permanently! I advise that you consult the expertise (e.g., mine) of an astronomer to view the solar eclipse with a telescope (also e.g., mine).
Andy Veh is an associate professor of physics, math and astronomy at Kenai Peninsula College.