StarWatch for the greater Lehigh Valley



Print Large Sky Charts For 9 p.m. EST:   NORTH | EAST | SOUTH | WEST | ZENITH

[Moon Phases]
Solar X-rays:  
Geomagnetic Field:  
Status Current Moon Phase

537    DECEMBER 3, 2006:   Geminid Meteors to Fly
The Geminid Meteor Shower, the best shooting star event of the year, just happens to coincide with the cloudiest month of the year, December. It seems as if nothing comes easily in astronomy, and the fact that luck plays a part in whether the weather will cooperate, just adds a bit of mystique and exhilaration if the night is or becomes clear. Geminids “fly” for about two weeks from the sixth of December through the 19th, but it is the evening of December 13 until dawn on the morning of December 14 that should be especially noteworthy. After midnight, but before a 1:45 a.m. moonrise on December 14, meteor rates could push as high as 50-75 events per hour from a rural location. Even from center city Allentown, without any direct glare from streetlights, at least a dozen Geminids should be visible per hour. These meteors will appear to diverge from a region of the sky just to the west (to the right) of Castor, which is the fainter of the two bright stars which compose the heads of the Gemini Twins, Castor and Pollux. By midnight the Twins will be high in the southeast. To the right will be Orion the Hunter, with its three equally bright belt stars which lie in nearly a straight line. To the Twins’ left will be Leo the Lion with bright Regulus and even brighter Saturn to Regulus’ right, separated by nearly the same angular distance as the Pointer Stars in the Big Dipper. Even if you are not into late night sky watching, Gemini will be easily seen in the east by 9 p.m. Many years ago, starting at 9 p.m. on a moonless Gemini night, I was able to count 15 meteors in a 20 minute period from my backyard in Coopersburg. It was one of the few times in my life that I was tempted to play hooky from school the next day. I didn’t. I’ll write more about the Geminids next week.

[Geminid Meteors]
Geminid meteors will radiate just to the west of the bright star Castor in the constellation of Gemini the Twins.  Gary A. Becker map and meteor images...

538    DECEMBER 10, 2006:   Staying Warm with the Geminids
All week Geminid meteors will rule. It is the year’s best display of shooting stars with Wednesday evening into Thursday morning bringing rates as high as 50-75 meteors per hour radiating just to the west of the bright star Castor in Gemini the Twins. See the map above this article, or read last week’s StarWatch to find specific information about where to look in the sky. One of your main goals in observing the Geminids is to stay comfortably warm. This can be accomplished by layering your clothing which helps to create warm pockets of air surrounding your body to lessen the effects of wind chill. Always protect your head, neck, hands, and feet. As much as 30 percent of your body heat can escape through the neck and head, so keep a scarf and balaclava handy because meteor observing is not exactly like playing football or soccer. I have found that in particular, cold ears, fingers, or toes, can easily become the ruination of any observing session, and if you start to shiver involuntarily, you are probably showing the early symptoms of hypothermia, a lowering of your core body temperature. Get inside at once. One way to keep warm is to simply take an occasional break and exercise. Run in place. Do jumping jacks. Whirl your arms around to drive blood into your fingers. Sure, the neighbors may think that you’ve finally flipped your wig, but then they are not the ones outside observing, are they? After getting all bundled up, I usually observe meteors by lying out under the stars in a sleeping bag. Make sure a foam mat or air mattress goes under your bag to keep the ground from robbing you of additional warmth. And don’t forget the red flashlight, paper, pencil, watch, and clipboard if you want to record your observations. Much success!

539    DECEMBER 17, 2006:   Vomit Comet
At the beginning of this school year, one of my former students, Jesse Leayman, invited me over to the Quakertown Airport to fly parabolas. If you have seen director Ron Howard’s film, Apollo 13, the remarkable story of how NASA and mission astronauts, Jim Lovell, Fred Haise, and John Swigert returned home from the moon after an oxygen tank exploded in their Service Module, then you’ve seen the effects of flying parabolas. In fact in the movie, hundreds of them were performed by NASA’s now retired KC-135A aircraft which was used to create weightless conditions for periods of up to 25 seconds. Yes, that’s right! The weightless scenes in Apollo 13 were actually filmed under zero-gravity conditions as the aircraft came over the top of a parabolic curve and began a free fall towards Earth. The maneuver involves putting the jet into a steep 45 degree climb, then riding over the top of the curve into a 45 degree decent. I guess you could say that this little exercise has its ups and its downs, not only for the plane, but the passengers as well. In NASA research stints, passenger reactions are equally divided into thirds with regards to becoming violently sick (hence the Vomit Comet), mildly nauseated, and just plain feeling groovy. In the dozen Cessna parabolas that were performed, Jesse and I experienced weightless conditions for two to three seconds, enough time for the dirt in the plane to become fully suspended and any untethered objects to float freely around the cabin. So how did I fare? I would place myself in the middle third of the participants, mildly nauseated. Okay, I did kibosh the 13th parabola because I would have slipped into the violently nauseated category, but then I was also taking pictures, a sure recipe for “cometus vomitus.” Photos are online.

[Mini Vomit Comet-1]
Executing parabolas in a Cessna is not quite as exciting as being in the Space Shuttle, but hey, it's a lot cheaper. I was able to experience about three seconds of weightlessness as can be seen in these Jesse Leayman photos.

[Mini Vomit Comet-2]

540    DECEMBER 24, 2006:   Subsurface Water Discovered on Mars
Amidst the fanfare of President Bush’s recent proposal to establish a permanent presence on the moon has been a little publicized story about the discovery of subsurface water on Mars. This finding just by itself should make us abandon the moon in favor of exploring the Red Planet. Since the early 1970s, satellite imagery of Mars’s surface has tantalized us with evidence that vast amounts of water were present in Mars’s earlier history. In addition, it became apparent that huge quantities of water were also stored beneath the surface of Mars as permafrost. Meteorite impacts, which release half of their kinetic energy as heat, created mudslides around craters. The movement of hot magma within the Martian crust released titanic quantities of water which gushed across Martian landscapes in floods that were unparalleled to anything known on Earth. The Martian rovers, Spirit and Opportunity, revealed minerals in the soil of Mars that could only have been formed in a water environment and then one-upped that discovery by finding that these bodies of water were more like Earth’s saltwater oceans. This meant a stable environment for long periods of time in Mars’s past, allowing dissolved minerals from rivers to collect and make these oceans brackish. Now we have conclusive proof that liquid water still exists beneath the Martian surface and occasionally spills out in small quantities creating stream-like flows. The newest ones are only several years old. Since planets rapidly become warmer with depth, it seems likely that life will one day be discovered in Martian reservoirs of liquid groundwater. Putting a human presence on Mars, where we can “live off the land,” makes much more sense then returning to the airless and waterless moon.

[Groundwater on Mars]
Groundwater on Mars:   A gully on the wall of an unnamed crater in Terra Sirenum, at 36.6°S, 161.8°W, was initially imaged by Mars (Global Surveyor) Orbital Camera MOC on December 22, 2001. It showed nothing noteworthy at the location where a change would later be observed. A group of nearby gullies exhibited an unusual patch of light-toned material. As part of the routine campaign to re-image gully sites using the MOC, another image of this location was acquired on 24 April 2005 (image S05-01463). A new light-toned deposit had appeared in what was otherwise a nondescript gully. This deposit was imaged again by MOC on 26 August 2005, at a time when the Sun angle and season were the same as in the original December 2001 image, to confirm that indeed the light-toned feature was something new, not just a trick of differing lighting conditions. In August 2005, the feature was still present. Modified NASA caption… The enlarged image below shows the same Martian crater after modification by groundwater between 2001 and 2005.
[Groundwater on Mars Enlarged]

541    DECEMBER 31, 2006:   Astronomical Treats for 2007
Numerous astronomical treats are in store for us during 2007, including the possibility of a meteor storm. There will be two total lunar eclipses and plentiful planetary gatherings to amuse us. Saturday, March 3, marks the first total lunar eclipse visible since October 27, 2004. A wacky eclipse it is, indeed, because at moonrise, 5:50 p.m. EST, Luna is completely inside the shadow of the Earth. As darkness envelops the eastern US, the full moon will emerge from Earth’s shadow as it gains altitude in the sky. Europe and the US East Coast are favored. On August 28 precisely the opposite occurs. The full moon, low in the SW, begins to enter the Earth’s shadow at 4:50 a.m. EDT. The eclipse becomes total just before moonset in a brightening blue sky. The West Coast and Hawaii hold the advantage with the moon at a much higher altitude. It will also be a banner year for meteor observing. Most of the best events are happening under favorable lunar conditions. Lyrid meteors fly in a moonless sky on the mornings of Apr. 21 and 22. The Perseids peak in the a.m. on Monday, August 13, with hourly rates of one meteor per minute expected. The moon is new the day before. The biggies of the fall, the Orionids, Leonids, and Geminids peak respectively on the mornings of October 21 (moonset, 12:30 a.m.), November 18 (moonset, 11:30 p.m.), and December 13-14 (thin crescent moon). A meteor storm has been predicted for the morning of September 1, with the West Coast favored as Earth scores a direct hit with the debris of long period Comet Kiess. Meteors will radiate from the constellation of Auriga. Since these predictions vary in accuracy, the entire US will be in the running for what promises to be an exciting night. Clear skies for 2007!

[March 3 Total Lunar Eclipse]
Make plans to view the total lunar eclipse of March 3.  Members of the Allentown School District Planetarium's StarWatch Team will have telescopes set up for the public at the Quakertown (PA) Airport starting at sunset.

December Star Map

December Moon Phase Calendar