The Sky This Week, October 20 – 27, 2015 !

The Sky This Week, 2015 October 20 – 27

Bright Moon, faint stars, and a reason to get up early.
The Northern Lights, 2015 October 9
Imaged from the M/V “Nordnorge” somewhere near Svolvær, Norway

We have returned from our trip to Norway, where our pursuit of the Northern Lights was amply rewarded. We now return to our weekly celestial updates.

The Moon waxes in the evening sky this week, wending her way through the autumnal constellations as she makes her way eastward along the ecliptic. Full Moon occurs on the 27th at 8:05 an Eastern Daylight Time. October’s Full Moon is popularly called the Hunter’s Moon, and it shares almost the same horizon geometry as September’s Harvest Moon. In far northern latitudes this causes successive moonrises to occur at about the same time on the nights around the full phase, and this “extra” light gave hunters a little more time to pursue game across the stubble of the harvested fields. Some Native Americans referred to it as the Leaf-falling Moon or the Nut Moon. Because the autumn sky is filled with mostly dim, ill-defined constellation patterns Luna’s journey this week is a lonely one; there are no bright objects along her path to meet with.

Early evenings will still find the Summer Triangle nearly directly overhead as twilight fades. The three stars Vega, Deneb, and Altair should be easy to track down despite the brightening Moon, and they can help you to find several interesting objects to look at during these cool crisp evenings. Almost smack in the middle of the triangle is the 3rd-magnitude star Albireo, which should be visible from just about any location. This star marks the “head” of Cygnus, the Swan. With the star Deneb marking the Swan’s “tail”, you should be able to trace out a large cross-shaped asterism that delineates the Swan’s body and wings, which (appropriately) seems to be flying south for the winter. Albireo itself is a wonderful target for the small telescope, revealing itself to be a double star with very colorful blue and gold components that I like to call the “Navy star”. Located some 430 light-years away, the two components may or may not be gravitationally associated. If they are their orbital period is in excess of 100,000 years!

Now turn your attention to the brightest star in the Triangle, Vega. Using binoculars you’ll see a close pair of stars just above Vega’s dazzling blue glow, Epsilon-1 and Epsilon-2 Lyrae. If you train a telescope with three or more inches of aperture and at least 100-power magnification on this wide double star you’ll see that each component is itself a close double star. For this reason this system is a popular sight at star parties, where it is known to amateur astronomers as the “Double-Double”.

Saturn continues to linger in the southwestern sky during evening twilight, and if you have a clear horizon in that direction you may be able to catch a final glimpse of him before he sets at around 8:00 pm. After that time we have a relative dearth of planets until the wee hours of the morning.

There are still two planets available during the evening hours, but you’ll need to have a good knowledge of the sky and a telescope to be able to see either one. Neptune reached opposition at the end of August and is currently located among the faint stars of Aquarius. At 8th-magnitude you’ll need at least a four inch telescope to resolve its pale blue disc between the stars Sigma and lambda Aquarii. Uranus is somewhat brighter at sixth magnitude and lies just over one degree south of Epsilon Piscium. Its pale greenish disc should be visible in a three-inch scope.

The main planetary action occurs in the pre-dawn sky with dazzling Venus, bright Jupiter, and a rather subdued ruddy Mars interacting over the next few weeks. You’ll have no trouble watching Venus close in on Jupiter this week. The two planets will be closest together on the mornings of the 25th and 26th when they will be separated by just over one degree. After that Venus will set her sights on Mars, passing the red planet on November 3rd. It’s well worth rising before the Sun to watch this celestial dance through the end of October while we’re still on Daylight Time. After November 1st everything will occur an hour earlier as we return to Standard Time!


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