NOVEMBER  2006

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533a  NOVEMBER 5, 2006:   Mercury Transits the Sun Midweek

This Wednesday between 2-4 p.m., the public is invited to view the planet Mercury transiting the disk of the sun. Dieruff High School’s StarWatch Team, composed of student and adult volunteers, will be manning properly filtered telescopes including specialty scopes optimized for solar viewing. The observing site will be Dieruff’s main parking lot paralleling North Irving Street. Transits of Mercury are rare, occurring about 13-14 times each century. Living in only one location, about half of them would be occurring in other parts of the world, making them invisible to us. Then there is the additional problem of cloudy or inclement weather that further limits the visibility of Mercury transits. The first and only Mercury transit that I saw was on the morning of Saturday, November 10, 1973. Several Allen High School students accompanied me to the eastern escarpment of Pulpit Rock, about seven miles south of Hawk Mountain, where we witnessed the sunrise with Mercury nearing the end of its trek across the sun. Since that time there have been four additional transits. The Mercury transits of Nov. 13, 1986 and Nov. 6, 1993 were not visible from the East Coast, whereas the transits of Nov. 15, 1999 and May 7, 2003 occurred under locally cloudy conditions. Sky conditions this Wednesday will dictate whether Lehigh Valley residents will have to wait an additional 10 years until May 9, 2016 to witness the next Mercury transit, a complete crossing of the smallest planet across the sun’s face. The 2016 event begins at 7:15 a.m. and ends nearly seven and one half hours later at 2:42 p.m. EDT. For Wednesday’s event, a go/no go decision, based upon weather conditions will be posted by 12:30 p.m. on the day of the event at the URL below.

533b  NOVEMBER 8, 2006:   Bright Taurids Can Dazzle

Recently, an e-mail written by John S. Sunny of center city Allentown prompted me to think of many other correspondences that I have received over the years during late October through late November. John Sunny noted that he had witnessed a meteor or shooting star, a piece of space dust from the dross of a comet, entering our atmosphere. But this event was unlike any other examples which normally “resembled a dim, pencil thin line in the night sky.” He continued with his excellent description saying that “This time, what I observed, was a brilliant heavy marker-sized line traveling relatively slowly in a downward trajectory and lasting about eight to 10 seconds before burning out. The light emitted was white changing to blue near the head, then changing to yellow, then orange closer to the tail. There also appeared to be sparks similar to an old-time sparkler at the tail.” Late October through early December is the time of the Taurid meteor shower, released debris associated with Comet 2P/Encke, noted for possessing the shortest orbital period of any comet circuiting the sun. Encke completes one orbital trek in only 3.3 years. Not only can Taurid meteoroids be larger than normal “shooting star” particles, making them brighter, but their slow 29 km/sec entrance velocity into the Earth’s atmosphere can indeed make these meteor events very long-lived, just like John Sunny described. Taurid activity peaks during the next week or so, as the moon wanes in brightness. Expect to see only a handful of these meteors each hour, even from rural locations. It may also take several hours of observing to witness that one memorable meteor wavering across the darkened sky, sparking and sputtering along the way to its demise.

534    NOVEMBER 12, 2006:   More Leonid Meteor Activity Expected

I’m going to become a Rain Man for hire. There’s money to be made in predicting astronomical events like the transit of Mercury that occurred under rainy Lehigh Valley skies last Wednesday. Municipalities and townships in rain-parched regions of the country would invite my StarWatch team to travel and enjoy the event from their area. They’d pay our travel expenses. On the day of the occurrence, as contracted, we would set up our astronomical gear, and it would rain. Of course, there would be a charge for this service, but only if rainy weather prevailed. We have a test case happening this weekend, the Leonid meteor shower, second of the three big meteor events of the fall. This year, we may have two maximums, one on Friday morning and the other on the following evening. Meteor rates during the former time will probably average the standard rate, about 15 shooting stars per hour from rural locales. The parent comet of the Leonids, 55P/Tempel-Tuttle is moving deeper into space from its 1998 passage around the sun, and particle numbers are dwindling. Around Saturday midnight into Sunday, activity could soar to 100 meteors per hour as the Earth traverses a strand of denser comet debris predicted by some astronomers. The Northeast is center stage, and the moon will not pose any interference during the night. Leonid meteors radiate from the head or Sickle of Leo, the Lion which starts rising, ENE about 11 p.m. These shooting stars careen into the atmosphere at 71 km/sec making them fast movers, often leaving wakes or luminous trails after their demise. By 3:00 a.m., Leo’s bright Regulus and even brighter Saturn, above Regulus, are just to the right of the point from which Leonid meteors will be radiating. Clear skies!

535    NOVEMBER 19, 2006:   The True Spirit of Giving

Last week, Jim Pinto from Spitz, Inc. visited the ASD Planetarium. Spitz in 1964 built the star projector which remains the workhorse of my star theater. As we were adjusting the planets, I recognized that there was a really magnificent planetary gathering occurring in the daytime sky. Mercury had just crossed the disk of the sun two weeks ago; Venus was coming around the back of the sun, and both Mars and Jupiter were caught within the sun’s glare. Only rogue Saturn was in the morning sky near Regulus in Leo the Lion. All of these planets would be spectacularly visible if only we just had a total solar eclipse in the next several days. Unfortunately, that is not going to happen. Because we cannot see these planets, it is really more of a nonevent than the dramatic conjunction that it should be. Jim’s visit, however, was not just about adjusting the planets. Recent events like a geocentric Earth that had fallen off my machine, problems with my moon, and the installation of a new star lamp “all had to be rectified within eight hours.” It was the the geocentric Earth that was the scariest. The cost to the planetarium would have been $3,551.00, but I received the part for free because Jim, in other service contacts before coming to Allentown, spoke about my financial plight. A planetarium director in the Midwest, who wished to remain anonymous, donated the part from his machine. Jim then had to get a double glass bulb containing a brownish liquid past airport security. Friend and mentor, Nick Knisely, Dean of Trinity Episcopal Cathedral in Phoenix, noted in a recent homily that the true spirit of giving was helping someone who was powerless to provide anything in return. I am not powerless, however, to say thank you for this most generous gift of kindness.

536    NOVEMBER 26, 2006:   Earliest Sunset Nearly Upon Us

Although the shortest day of the year for the Northern Hemisphere, winter solstice, happens for North America on December 21, the earliest sunset for the Lehigh Valley, 4:34 p.m., occurs on December 7, making it seem as if this day is really the solstice. Our waking hours are centered more around sunsets than sunrises. After December 7, the sun begins to set later in the evening, but it overcompensates by rising later in the morning, continuing the trend of decreasing the amount of time when the sun is visible until solstice day. The latest sunrise for 40 degrees north latitude happens on January 5, almost a full month after the earliest sunset. This discrepancy between the earliest sunset, the latest sunrise, and the time of winter solstice is a function of Earth’s oval-shaped orbital path around the sun. The time kept by clocks uses a fictitious sun which moves at a uniform rate, crossing the meridian (due south) in precise 24-hour intervals. While the Earth is spinning, it is also orbiting the sun, causing the real sun to move about one degree to the east each day. This shift in the sun’s position is corrected by adding an extra four minutes to Earth’s spin period to bring the sun back to the meridian. But these extra four minutes do not necessarily bring the real sun precisely back to the meridian because Earth’s orbital speed varies. From November through early February, when Earth’s orbital motion is fastest, the sun shifts farther east than the Earth’s rotation can compensate. In December, while the days are still shortening, the real sun is actually running ahead of the clock sun, causing sunsets to occur at an earlier time than expected. By January, the continued effects of Earth’s faster orbital motion, causes the real sun to run behind the fictitious sun, making sunrises occur later.