Astronomy From Your Back Yard - 10/27 to 11/2 2010

Thursday, October 28 2010 @ 09:27 pm EDT

Contributed by: dgrosvold

By Dave Grosvold

This week the Moon is well on its way toward Last Quarter, which occurs at 7:47 AM Saturday, Oct 30th. Forecasts call for several clear evenings into the weekend, an excellent opportunity for a little night sky observing -- especially since the Moon won't rise until after 11:00 PM CDT.

NASA, ESA, AURA/Caltech, Palomar Observatory
During the latter part of the week, yellow-bright Capella is shining in Auriga, well up in the northeast by mid-evening. Look off to its right in the east for the Pleiades, or Seven Sisters.

The beautiful Pleiades (PLEE-ah-deez,) star cluster is also known as Messier 45 (M45), one of the original 103 objects Charles Messier catalogued in 1771 as objects to avoid while comet hunting, which was his main passion. Messier's list became better known to history as the first list of interesting non-stellar objects in the night sky.

The Pleiades are probably the most well-known star cluster visible to the naked eye. A group of young, blue-hot stars surrounded by nebulosity, the cluster is thought to be less than 100 million years old. By contrast, the Sun is thought to be more than 4.6 billion years old. In Japan, the Pleiades cluster is known as Subaru, and is graphically depicted as the corporate logo for the automaker of the same name.

Below the Pleiades, spaced by about a fist-width at arm's length, is the orange giant Aldebaran, the brightest star in the constellation Taurus. A close neighbor, Aldebaran lies only about 65 light years distant from our Solar System. Aldebaran (Al-DEB-a-ran) means “the follower”, presumably because it appears to follow the Pleiades. For the Seris of northwestern Mexico, Aldebaran is there to provide light for the seven women giving birth (the Pleiades.)

Every year for several days around October 29th, the bright star Arcturus, in Bo÷tes, takes a special position sparkling in the fading twilight low on the west-northwestern horizon. This position marks the spot where, months earlier in June and July, the Sun stood at the exact same time of the evening. Then, the summer daylight was still strong in the evenings, now the autumn light is fading and this much smaller, scintillating gem is all that remains in the west, the Ghost of the Summer Sun, marking the mid-point of autumn.

Mars is still hanging around very low in the southwest after sunset as well. Use binoculars to scan for it early in twilight. Don't confuse Mars with Antares, which is off to Mars' left and just a tiny bit brighter. The name Antares comes from Ancient Greece, so named because the star can easily be mistaken for Mars. Antares literally means "holds against Ares" (Ares is also known as Mars in Roman mythology.)

Jupiter still shines high in the southeast between Pisces and Aquarius rising high into the south-southeast as the evening wears on. Right now, it is by far the brightest star-like point in the sky. Jupiter continues to appear a big 47 or 48 arc-seconds wide in a telescope or binoculars.

Once again, the tiny black shadows of two of the Galilean Moons, Europa and Ganymede, fall on Jupiter's face from 11:16 PM CDT Saturday evening to 1:59 AM CDT Sunday morning. These can only be caught with the aid of a small telescope -- binoculars won't do.

Saturn is visible in Virgo, low in the east in early dawn. The best time to try observing it with a telescope is in moderately bright morning twilight, perhaps an hour before sunrise, when it will be less blurred by the low-altitude atmospheric mess. Saturn's rings have opened to 7░ or 8░ from edge-on, and so are more prominent than they were just a few months ago.

Uranus is still within 3░ east of Jupiter. Neptune, in Capricornus, is high and almost due south at about 9:00 PM CDT.

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