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The Sky This Week, 2010 October 5 - 12

Triangles, Squares, Jupiter, and a Comet!


Jupiter, with the Great Red Spot and "Little Red"
Imaged on 2010 OCT 3, 03:40 UT
from Alexandria, Virginia, USA

The Moon returns to the evening sky as a waxing crescent as the week ends. New Moon occurs on the 7th at 2:44 pm Eastern Daylight Time. Look for Luna’s fattening crescent in the southwestern sky shortly after sunset on the evening of the 9th. If you have a pair of binoculars, see if you can pick out the ruddy glow of the planet Mars about five degrees above the two-day crescent. Two nights later the Moon may be found about four degrees east of the ruddy star Antares, perched just above the southwest horizon as twilight ends.

You still have much of the week to enjoy the best of the autumnal sky before the Moon’s brightness begins to wash out the sky’s fainter objects. October has always been my favorite stargazing month, since the temperatures usually haven’t hit the freezing point yet and the summer’s best targets are still in view for the first couple of hours after dark. Evening astronomical twilight ends at around 8:15 pm, and at this time the stars of the Summer Triangle are directly overhead. The great star clouds of the Milky Way wend toward the southwest, and if you sweep the area between the Triangle and the horizon with binoculars or a small wide-field telescope you can catch many of the bright star clusters and nebulae that inhabit this stretch of the sky. By midnight another geometric figure, the "Great Square" of Pegasus straddles the meridian, with bright Jupiter parked just below. This area of the sky offers a "window" to distant external galaxies as we look south of the Milky Way’s plane. On clear nights from dark skies you can easily pick up the lozenge shape of misty light that betrays the Great Andromeda Galaxy in your binoculars, and if your surroundings are very dark you can easily see it with the naked eye. Draw an imaginary line from the lower right star in the Great Square through the upper left star to point yourself to our nearest large galactic neighbor. Larger telescopes reveal subtle detail in Andromeda’s delicate haze, and patient sweeping of the area around the square will show dozens of more distant galaxies to the sensitive eye.

High in the north at the midnight hour look for the "W"-shaped grouping of stars that portray Cassiopeia, one of the major figures in the Perseus-Andromeda myth. Binoculars and dark skies this week offer the possibility to see a fuzzy visitor to the inner solar system, Periodic Comet Hartley-2, which is making one of its closest approaches to Earth in its 6.46 year journey around the Sun. It will pass a mere 11 million miles from Earth on October 20th, and right now it is an easy target for binoculars and small telescopes. As the week opens it may be found below the left side of the "W" of Cassiopeia; as the week evolves it moves down toward the head of the wishbone-shaped constellation of Perseus. Look for a softly glowing greenish glow with a brighter center.

Jupiter is now the showpiece of the overnight hours. His bright glow has tricked many people into mistaking him for Venus, but the latter planet is now approaching solar conjunction and would never be found in this part of the sky at midnight. Old Jove has been rewarding owners of small to medium sized telescopes with wonderful views of his ever-changing cloud bands and shuttling moons. At a star party that I attended last weekend a young girl expressed delight at seeing the four Galilean moons in her rickety "department store" telescope. Her reaction at looking through several of the amateur telescopes set up nearby was even more enthusiastic. We’ll be able to continue enjoying Jupiter’s antics for the rest of the year, so keep an eye on him for constant changes.

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