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University of Minnesota
September 21, 2012
Composite image of Centaurus A, revealing the lobes and jets emanating from the active galaxy's central black hole. Credits: ESO/WFI (optical); MPIfR/ESO/APEX/A.Weiss et al. (submillimeter); NASA/CSC/CfA/R.Kraft et al. (X-ray).
By Deane Morrison
October belongs to Pegasus and the water constellations, which float through the southern sky after nightfall.
Reigning supreme high in the south are the Great Square of Pegasus and, stretching from its northeast corner, a string of three stars in the constellation Andromeda. Above the middle star, you may see a faint oval smudge; this is the Andromeda galaxy, the Milky Way's largest close neighbor.
Below the Great Square, the Circlet of Pisces is easy to find. Moving southwest from the Circlet, the Y-shaped Water Jar is the centerpiece of spidery Aquarius, the water bearer. The water bearer refers to Ganymede, a handsome youth whom Zeus (Jupiter) made cupbearer to the gods. Now, it's also one of Jupiter's four Galilean moons.
Southwest of Aquarius is unobtrusive, chevron-shaped Capricornus, the sea goat. And the lonely star far to the south is Fomalhaut, brightest in Piscis Austrinus, the southern fish.
A dim Mars manages to stay above the sun's afterglow, but the evening sky's real planetary presence is Jupiter. As October opens, the brilliant planet rises around 9:45 p.m. CDT, and it appears earlier every night. Jupiter sojourns between the horns of Taurus, not far from the bright star Aldebaran, the eye of the bull.
In the morning sky, Venus is a beacon in the east. Our sister planet has a close encounter with Regulus, the brightest star in Leo, on the 3rd and gets a visit from a crescent moon on the 12th.
October's full hunter's moon falls on the 29th. It will be a beauty, rising close to sunset and only about three hours past perfect fullness. This moon draws its name from the fact that in October the fields have been harvested and the open fields make hunting easier. And with winter approaching, more urgent.
The moon will be past full when it rises on Halloween during prime trick-or-treating time. Whether they know it or not, the children (and some adults) dressing up that night will be re-enacting the ancient Celtic rituals of Samhain (rhymes with COW-en), an astronomically based holiday that marked the start of the dark half of the year.
At sunset that day, the seam between our world and the netherworld opened, releasing evil spirits that had been banished from the human realm since May Day. People tried to ward off the feisty spirits with lanterns made from hollowed-out gourds, or to appease them by leaving offerings of food. Samhain was one of four cross-quarter days falling midway between an equinox and a solstice.
The University of Minnesota offers public viewings of the night sky at its Duluth and Twin Cities campuses. For more information and viewing schedules, see:
Duluth, Marshall W. Alworth Planetarium: www.d.umn.edu/planet
Twin Cities, Minnesota Institute for Astrophysics (during fall and spring semesters): www.astro.umn.edu/outreach/pubnight
Check out the astronomy programs at the University of Minnesota's Bell Museum ExploraDome: www.bellmuseum.umn.edu/ForGroups/ExploraDome/index.htm
9/21/12 Contact: Deane Morrison, University Relations, (612) 624-2346, firstname.lastname@example.org
Find U of M astronomers and links to the world of astronomy at http://www.astro.umn.edu.