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27 Sep 2018

October Astronomy: A Late-Month Procession of Stars Is Both Led and Concluded by Arcturus

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The moon passes the three bright outer planets at dusk Oct. 11-18. Venus, in transition from the evening to the morning sky, is lost in sun’s glare for most of month. Around Halloween, Arcturus, low in west-northwest at dusk, leads a procession of bright stars through the night, and brings up the rear low in the east-northeast at dawn.

At dusk: In early October, Venus sets very soon after sunset; it shows up on our evening twilight sky map for just the first few days of the month. Look for soon-to-depart Jupiter very low in the southwest to west-southwest; Saturn in the south-southwest; and Mars in the south-southeast. Before month’s end, Mercury begins an unfavorable evening appearance during which it will remain very low. Binoculars will come in handy for spotting Mercury within 5 degrees of Jupiter Oct. 25-Nov. 1. They’re closest, 3.2 degrees apart, on Oct. 28.

Stars: Arcturus is in the west to west-northwest; the Summer Triangle of Vega, Altair and Deneb is overhead; Antares is in the southwest to the lower right of Saturn; and Fomalhaut is low in the southeast. Capella rises into view in the north-northeast.

The moon: Use binoculars to catch the young crescent moon before it sets within 10 degrees south of west very soon after sunset on Oct. 9. Follow the moon daily at evening mid-twilight, starting as a thin crescent, very low in west-southwest on Oct. 10, and ending full, just risen north of east, on Oct. 24. Watch the waxing crescent moon pass Jupiter on Oct. 11 and Saturn on Oct. 14. On the evenings of Oct. 17 and 18, the gibbous moon appears near Mars.

At dawn: No planets show up on our morning mid-twilight sky map (below), but Venus,beginning a morning appearance, rises just 30 minutes before the sun on Oct. 31. Early in the month, can you spot Canopus as it passes 3 degrees above the horizon, due south? The huge Winter Hexagon is then centered high in the southern sky. Starting at Sirius, its brightest and southernmost star, and going clockwise, we find Procyon; the “Twin” stars, Pollux and Castor; Capella at the northern vertex; Aldebaran; and Rigel. Reddish Betelgeuse lies inside the Hexagon. Chasing the Hexagon across the sky is Leo, the Lion, whose brightest star is Regulus. In mid-October, Arcturus rises into view in the east-northeast, followed by Spica in the east-southeast just before month’s end. Using binoculars, look about 15 minutes before sunrise at month’s end, and you might spot a crescent Venus just risen in the east-southeast. It’ll be much easier to spot Venus in November, when it will rise farther ahead of the sun.

Follow the waning moon in the mornings Oct. 1-8. On Oct. 1, it’s above Betelgeuse in the south. On Oct. 2, the moon passes last-quarter phase, half full in Gemini, and 90 degrees or one-quarter circle west of the sun. On Oct. 3, the moon passes south of Pollux, and on Oct. 5 and 6, it’s near Regulus. The last easy chance to see the old moon will be on Oct. 7, followed by a challenging ultra-thin crescent for binoculars 2 degrees up in the east 25 minutes before sunrise on Oct. 8. Another round of morning twilight moon viewing begins with the full moon low in the west on Oct. 24. The waning gibbous moon will appear near Aldebaran on the morning of Oct. 27. On Oct. 30, the moon is nearly between Pollux and Procyon. On Oct. 31, for the second time this month, the moon reaches last quarter phase.

October’s all-night parade of stars: Each year around Oct. 29-30, there is a procession of bright stars across the night sky from dusk until dawn. Arcturus, low in west-northwest at dusk, leads the parade. On the evening map, Arcturus is followed by the Summer Triangle (Vega, Altair and Deneb), which, in turn, is followed by another geometric figure, the Great Square of Pegasus. Rising into view in the east-northeast before evening twilight ends is the Pleiades star cluster, or Seven Sisters. Following the Pleiades is Aldebaran, whose name translated from Arabic means “the follower,” although the star also marks the eye of Taurus, the Bull.

Rising later in evening, after Aldebaran, is Orion, the Hunter, with the “Mother goat” star Capella far to his north, and Gemini the Twins to his northeast. Rising after Orion are his two dog stars, Sirius in Canis Major, and Procyon in Canis Minor.Several of these stars form the huge, aforementioned Winter Hexagon, or Winter Ellipse, following the Pleiades across the sky. Leo, the Lion, including the bright star Regulus, follows the Winter Hex. Maybe Leo is checking out his menu,which includes a Hunter (Orion, with Rigel and Betelgeuse), some beef (Taurus with Aldebaran), a mother goat (Capella in Auriga, the Charioteer), Twins (Pollux and Castor in Gemini) and two dogs (Canis Major and Canis Minor, including Sirius and Procyon). The next bright star after Leo’s Regulus is Arcturus, low in east-northeast as morning twilight begins. And so, this golden-orange star, symbolic of autumn colors, both leads the procession of stars through the night skies of late October … and brings up the rear! This happens each year as the sun passes 33 degrees due south of Arcturus a day or two before Halloween. The Summer Triangle will fill this same role, as leader and follower in an all-night procession of stars, in mid-January.

Star parties: The website of the Astronomical Society of the Desert at www.astrorx.org has a listing of our evening star parties at two locations: Sawmill Trailhead, our high-altitude site (elevation 4,000 feet), will have our monthly star party starting at dusk on Saturday, Oct. 6. Our primary, more-accessible star-party site for most of the year is the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument, on Highway 74, within four miles south of Highway 111 in Palm Desert. Monthly star parties held there will resume on Saturday, Oct. 13. Listings of star parties on the website include maps and directions for both locations. Star parties can be cancelled in poor observing weather.

Also, beginning in late October, check the Impromptu Star Parties link on the webpage. I’ll be offering sky watches in Palm Springs at the pedestrian bridge over Tahquitz Creek at North Riverside Drive and Camino Real—some at dusk to catch Saturn while it’s still visible, and some at dawn to welcome Venus as morning star.

Abrams Planetarium publishes a monthly Sky Calendar with an evening sky map. Subscriptions are $12 per year at www.abramsplanetarium.org/skycalendar for three printed issues mailed quarterly. The current 50th Anniversary issue for October 2018 is available below.

Wishing you clear skies!

Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing sky watching opportunities for a variety of groups in the Coachella Valley. Robert D. Miller did graduate work in planetarium science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.

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