Planet admirers have been waiting for August with eager anticipation. This month, the two most impressive planets in our solar system both come to opposition: Saturn on the 2nd, and Jupiter on the 19th. At opposition, a planet is directly opposite the sun resulting in it being above our horizon all night and shining at its absolute brightest.
Saturn will sparkle at magnitude +0.2 and subtend an angular size of 18.6 arc seconds on August 2. Its magnificent rings are tilted at an angle of 18 degrees with Saturn’s north pole angled toward us. Eight of its many moons will be visible in amateur sized instruments. At least five of them are visible in telescopes as small as six inches. Saturn remains well-placed all month.
Jupiter reaches magnitude -2.9 and 48.9 arc seconds in diameter this month. Its disk is bejeweled with intricate details including its bright zones and dark bands. Its most striking features are the two equatorial bands that are themselves dotted with oval storms and bordered by rippling edges with an endless parade of notches, barges (cyclonic regions), and festoons (looping swirl-like features). The iconic Great Red Spot (GRS) transits the disk about every 10 hours. While the GRS has shrunk in size in recent years, it has developed an intense orange color that makes it more visible.
Jupiter’s four bright Galilean moons provide their own show as they shift back and forth, passing in front of and slipping behind the planet. They frequently cast their dark shadows onto Jupiter’s disk as they transit. The moons also eclipse and occult one another making for dramatic observing opportunities.
In the first week of August, a wanning crescent moon will enhance the pre-dawn sky and in the second week, a waxing crescent will adorn the western sky just after sunset. It will make a beautiful companion to bright Venus, which is getting low in the west. Check it out early on the evening of the 10th. Around the 20th, the nearly full moon rises with Saturn and Jupiter making for a remarkable naked eye view, looking southeast, just after sunset.
Meteor watchers also have cause to welcome August. Conditions for this year’s Perseid meteor shower are nearly perfect. With the moon out of the way early, there is nothing to mar the event that is typically the best shower of the year. If monsoon clouds cooperate, you might count 60 or more per hour from a dark sky. The Perseids occur each August when Earth passes through debris left behind by Comet 109P/Swift-Tuttle. They usually are seen from mid-July until late August. The best time to watch will be on August 12 from about 2am until dawn, but even the late evening hours of August 11 should provide a good show. Be sure to allow yourself time to dark adapt. The Perseids get their name from the fact that the meteors seem to emanate from a point within the constellation Perseus. Meteors will be seen all over the sky, however, so it doesn’t matter which way you face.
August’s full moon on the 22nd is a “Blue Moon”! Did I confuse you? August doesn’t have two full moons you say? You’re right, of course, but this month’s full moon is a Blue Moon in the original sense. The modern use of the term originated with the 1937 Maine Farmers’ Almanac and referred to the third full moon in a season having four. The more popular definition of it being the second full moon in a calendar month was inadvertently created in the March 1946 issue of Sky & Telescope magazine in an article by James Hugh Pruett who misinterpreted the procedure for naming a Blue Moon. Many media stories in the past few decades have established this “incorrect” definition as the dominant one. For the purists who stick to the original, this month’s full moon qualifies.
The University South Foundation’s Patterson Observatory is closed for monsoon, but will reopen with a public observing session on September 9. Members of the Huachuca Astronomy Club will be on hand to show guests around the sky. Saturn, Jupiter and a slender crescent moon will be the major targets of the night. Admission to the event is free, but space is limited and guests must register on-line at universitysouthfoundation.com. Pull down the Patterson Observatory tab to find the registration form. The observatory is located on the University of Arizona, Sierra Vista campus at 1140 N. Colombo Avenue.