Volume XVIII No. 6 March 2007 gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg Latitude: Sharing a Sky By Gordon Bond Once upon a time, we humans were better "in tune" with the hints Mother Nature threw at us. We kind of had to be. Knowing to read the sky or animal behavior could very well be the difference between…well…living or not. Things like calendars and The Weather Channel have made a lot of that obsolete - or at least more specialized disciplines. As amateur astronomers, however, we still retain some of that connection. We learn to associate not only the appearance of certain constellations with specific seasons, but also where in the sky they appear. Here in New Jersey, Orion is an obvious sign of winter, yet it doesn't get all that high off the horizon. It always brings back personal memories of when I first bought my telescope and had to drag it all over my parent's backyard until I could get a clear shot at M42 through the trees and curling smoke of a neighbor's chimney. It was as if the mighty hunter was forced to climb his way across the sky through the barren branches. Similarly, the height of summer was always heralded by Cygnus winging through the thick of the Milky Way, high above my head. This perception is, of course, a function of the lati- tude I've spent my formative years at. If I had lived farther north or south, my seasonal associations would be somewhat different. And had I grown up south of the equator, the night sky would be a completely different show. We sometimes comment on how the sky appears different from other parts of the globe. But I thought it might be an interesting exercise to approach that concept from the exact opposite direction - to ask what other countries share my latitude and, therefore, my New Jersey perspective of the sky? A world map and a ruler is pretty much all I needed. I drew a line, left to right (east to west), from the very northernmost and southernmost tips of New Jersey to form a NJ-sized swath clear around the world. This represents an area roughly 150 miles long, between 38 degrees and 41 degrees of north latitude. Unless you're a student of geography, a map fan, or experienced world traveler - none of which I can specifically claim - there were some surprises as to just what this band covered when extended around the globe. I sort of intuitively knew if I headed west, into North America, I'd cross half of Delaware, lower Pennsylvania, a bit of Maryland, a northernmost tip of Virginia, northern West Virginia. But the healthy cen-tral chunks of Ohio, Indiana and Illinois, seemed a little less obvious and I never really considered that (continued page 7: Latitude) Define "Full Moon" by Dr. Lew Thomas I have asked a number of people to define a full moon. Most tell me that the Moon is full when it is exactly opposite the Sun. If this were so then a full moon could only occur during a total eclipse of the Moon. This is the only time the Moon, as seen from Earth, is exactly opposite the Sun. Even then, the Moon by this definition could only be full when its center tracks over the center of the Earth's shadow. If we defined a full moon in this manner, there would only be one or two full moon's each year at best. Others say the full moon is a Moon of opposites. It rises at sunset and it sets at sunrise. This, too, cannot be true because if one does some exact measurements we find that this sort of timing is only approximate. So how do we define a full moon? Astronomers, that is the IAU, define a full moon as one whose celestial lon-gitude is 180° removed from that of the Sun. Celestial longitude is measured along the ecliptic in an easterly direction. Zero degrees of celestial longitude occurs at the vernal equinox. Now you see with this definition, the moon can be anywhere along its orbit so long as it is 180° from the Sun when full. The lunar orbit is tilted 5.15° with respect to the ecliptic. Sometimes the Moon may be at its node (where its orbit crosses the ecliptic) and sometimes it can be as much as 5.15° above or below the eclip-tic. Except for the rare cases when the Moon is at one of its nodes and also 180° from the Sun, the full moon is NOT opposite the Sun. Also, except for those cases, the full moon does NOT rise exactly at sunset or set ex- actly at sunrise. To complete the picture, the new moon, first quarter, full, and last quarter occur when its central longitude differs from the sun by 0°, 90°, 180°, and 270°, respectively Now you can ask your friends, "What is a full moon?", and see how many can come up with the right an-swer. The Algol Paradox by Dr. Lew Thomas Massive stars go through their life cycles more rapidly than less massive stars. The more massive a star, the quicker it moves off of the Main Sequence to become a giant, a sub-giant, or a super giant… Right? Well, not always. Take Algol, for example. It consists of a bright star and a darker companion. As we all know, whenever the dark companion passes in front of its bright neighbor, Algol's brightness suddenly drops from 2.2 to 3.5 in mag-nitude. This is more than a 2.5 times drop in luminosity. Algol's brightness change was first explained by Good- ricke in 1782 and confirmed by spectroscopic measurements in 1889. Algol is a spectroscopic, eclipsing bi-nary. We note that the drop in brightness is much greater when the dark companion (Algol B) moves in front of the bright companion (Algol A) than when the reverse is true. Among other things, this means that Algol B is larger than Algol A since it cuts off all of A's light. The passage of Algol A in front of Algol B only reduces the combined light very slightly. This also indicates that A is smaller than B and therefore cannot interrupt much of B's light. It turns out that Algol B is a sub-giant whereas Algol A is still on the Main Sequence. All well and good, ex-cept that A is much more massive than B (determined from the fact that B is farther from the common barycen-ter than A). Here we have a more massive star still sitting on the Man Sequence while the lass massive one has long since left the sequence and evolved into a sub-giant. How can this be? The answer is that B started out much more massive than A and so evolved more quickly. However, B has by now lost much of its mass to A making it, in the end, a more massive A. The fact that the more massive A is still on the main sequence has been called the Algol Paradox, but now we know the answer! Time Change - The Sooner, the Bitter by Bonnie B. Witzgall Hey - it's that time again! Time to Spring Ahead and lose that precious hour of darkness because the Federal Government says so. But wait! This is 2007 and federal mandate says we must change our clocks 3 or 4 weeks earlier than usual to conform to this year's new directive of Daylight Savings Time. This 'Spring Ahead Sooner' is supposed to help cut the use of gas and oil and curb the high cost of energy. Americans trying to save energy will not impress the oil producing counties of the Middle East. Clean up crews busy from Floridian tornadoes and New York State snowstorms will not show extra inspiration. They will just begin their shifts sooner when the sun appears to 'rise earlier'. Some astronomers never liked this idea of altering their local mean times, ei-ther. Three states, Hawaii, Indiana and Arizona do not even acknowledge this annual time change… and this year; neither will your pre programmed appli-ances! Most VCRs, computers, high end cell phones, Blackberry© and iPod© units are automatically set to change their internal clocks at the end of April, the 'old' beginning for America's daylight savings time. However, not all our pre programmed devices realize the National Government has flexed its muscles and meddled with this year's time regulations. Our automated machines will dutifully change themselves in April, as encoded during their manufacturing stage. Since the Daylight Savings time begins in March this year, today's users will have the task of manually altering their electronic gadgets prematurely, conforming to their States' local time changes. The electronic machines will require some sort of 'e patch' or program update to retain their proper readings on 'local mean time'. Re programming blinking VCR or time sensitive equipment in a motor vehicle can be a nightmare, but this Spring we have no choice. As you struggle to correct your countless time measuring devices this month, just remember the plight of the local astronomer. We may lose that hour of darkness a month sooner, but be grateful that our Go To scopes don't care about any Legislative time mandate. Thankfully, our instruments and ourselves respectfully calculate time by a Higher Authority. (Ed. Note: up-to-date versions of the Microsoft operat-ing systems handle this revised DST schedule automati-cally. If you have an older system that requires manual ad-justment on March 11th, be sure to remove the checkmark for Daylight Savings in your computer's clock display. Oth-erwise, your clock will spring ahead again on April 1st.) Letter From Joe Montani (Ed. Note: When Joe heard of the recent passing of long-time AAI member, George Nalisnik, he sent the following email. It is reproduced here with Joe's permission.) Dear Ray, It hits me sorrowfully to hear of the passing of George Nalisnik. George was an enormous help and inspi-ration to me in making Optics and precision mechanical components, and in integrating optics and mechanics, and in knitting people together through the use and making of fine telescopes. He has been one of my mentors, and very dear friends. He was generous, and made some parts for me, and made gifts of them to me. He had the highest standards, and he made his work look "easy": this urged others on, quietly, to work at his level, if only we could, and to help others, as he always did. His 8-inch homemade Maksutov was a beauti-ful wonder to all of us, and it gave us views of planets, say, which were so detailed and so perfect that we could have had no right to ex-pect such performance from any 8-inch aper-ture. We thought he must have some "slides" inside the telescope which he was using to project these fine images into the eyepiece. He was also the best astrophotographer I have known, and made wonderful photos at very long effective focal-lengths of planets and of lunar details, and of course he did all the film-processing and print enlarging in his own home. He was a consummate worker! I'm sorry to hear of the passing of Roy Smith. My sainted Dad warned me of such passings, many years ago when I was a kid: he'd say, "Joe, people are dying now who have never died BEFORE!" I understood it in Dad's lighthearted humorous way, but I also took it seriously as an encouragement to "not waste time." Dad would have been 99 years old in April this year. He and Mom would have celebrated their 71st wedding anniversary on February 15, the day after Valentine's Day, just a few days ago. But, alas, Dad left this mortal coil a few days after the Bicentennial, and Mom joined him five years later. With thanks again, and best wishes. Please take good care of yourself, Sincerely, --Joe Stewart's Skybox By Stewart Meyers Sometimes, the idea for an article falls into your lap. This was almost literally the case. By now, I am sure that just about everyone at AAI has heard about the commotion and media circus that resulted when a small meteorite crashed through the roof of a house in Freehold (not all that distant from where I live). This has prompted me to discuss meteorites. Some of the more astute readers of this column may recall that I did touch on cosmic impacts in an earlier column. But those were the result of very large objects. This time, I will focus on much smaller ones. Also, since there are a number of AAI members who are far more knowledgeable about the physical nature of meteorites (most notably Al Witzgall) than I am, this article will focus more on the history of meteorites. At the end, I will include my comments about the Freehold meteorite and how the situation was handled. Ancient Irons Not In the Fire Although people in ancient times had very limited knowledge of the true nature of astronomical objects or of science in general, they were quite open to the idea of objects falling out of the sky. This is not too surprising since most mythologies and all major religions have stories about their deity (or deities as the case may be) throwing things from heaven to either to help (as in the case of manna in the book of Exodus) or to punish people (thunderbolts, fire, brimstone, etc). Because of this, meteorites were frequently considered worthy of worship. The ancient Greeks built a temple to Artemis at Ephesus in honor of a meteorite +that fell in the area and the Black Stone in the Kaaba in Mecca was, up until recently, thought to be a meteorite. It is now thought to be a piece of impac- tite, a glass formed when sand is subjected to a large meteorite impact and melts. This is borne out by leg-ends claiming that the stone was originally honey-colored but turned black over time (which is how im-pactite weathers). Perhaps another reason why meteorites were awe-inspiring in ancient times was that nickel-iron meteorites were the first exposure humanity had to iron that wasn't embedded in an ore. In essentially a preprocessed form, some societies used nickel-iron meteorites to fashion primitive iron tools, like the Greenland Inuit did from the fragments of the enormous Cape York meteorite, the one known as Ahnighito being the largest, which was brought to New York by Admiral Peary in 1893 and is now exhibited in the American Museum of Natural History in New York http://tinyurl.com/2zqfxb. Nickel-iron me-teorites might have been what inspired the Hittites to discover how to smelt iron from iron ore and become the first civilization with true iron metallurgy. That Darn Aristotle Eventually, in Roman times, the philosophies of Aristotle took hold and became the dominant view on the natural world. When Christianity embraced the philosophy, it became the only view. In Aristotelian cosmology with the idea of the four elements (Earth, Air, Fire, and Water) and a separate sphere for each, meteorites became a troubling puzzle. So, rather than question the official view and church dogma, people decided that meteorites were created as a result of lightning through some unknown process. Since there was very little science in those days, nobody could find any way to challenge that view. Here Come The Falling Stones That was the way things stood for over a thousand years. But, in 1492, just outside the town of En-sisheim in France (though the town was considered part of Germany at the time, hence the name), a boy reported seeing a large (127 kg or 279 pound) rock fall out of the sky. The local authorities went out to investigate and they did indeed find a large rock. Since it did not look like any local rocks, it was concluded that this was a strange supernatural event. Soon, the meteorite gained wide renown and many people wanted a piece of the rock (this was in the days before Prudential Insurance even existed) so they simply chipped off a chunk. Eventually the town magistrate took possession of it. By that time, the me-teorite was reduced to about half the size it was when it was discovered (55 kg or 121 pounds). In 1535, the Emperor Ferdinand of Austria took the meteorite and placed it on display at the Regency Palace in the town. Today, it can be seen at the old town hall in Ensisheim. Despite the evidence of the meteorite, scientists did not believe that meteorites really came from the sky. Even after the writings of Copernicus and the observations of Galileo discredited Aristotelian cosmology, the old belief in an Earthly origin for meteorites still held on. But, as the 18th century was coming to an end, things would change. Apparently inspired by a large number of meteorite reports, German scientist Ernst Friedrich Chladni published a book in 1794 that claimed meteorites ac-tually came from space. However, the book was not well received by the scientific community who felt me- teorites were only reported by ignorant peasants and crackpots.. Then, in 1803, hundreds of small meteorites fell on the town of L'Aigle, in France. The French Academy of Sciences sent Jean-Baptiste Biot to investigate the report. After interviewing numerous witnesses and examining the meteorites, he concluded that the meteorites actually came from space. Due to the thoroughness of Biot's report, the French Academy of Sciences accepted this finding. Eventually, even American scientists would come to the same conclusion. In 1807, a local judge in Weston, Connecticut spotted a fireball, which zipped across the sky and disappeared nearly overhead. The man heard a noise and saw a stone fall to the ground. He contacted Yale University and two professors investigated the matter. Like Biot, they found that the meteorites came from space. However, there were still some skeptics, including one who is well known to every American - Thomas Jefferson. In addition to being a statesman, writer, and historian, Jefferson was probably the most scientifically literate man in American political history. His interests included linguistics (mainly Native American languages), architecture, engineering, paleontology, and other fields. When Jefferson heard about the Yale report on the meteorites, he supposedly said "I would rather believe that two Yankee professors would lie than believe that stones fall from heaven." This skepticism was probably due to the fact that many people at that time found it hard to conceive of anything in the solar system other than the Sun, the planets, and the occasional comet. Doing The Science Though the idea of meteorites from space became accepted in the 19th century, the study of them progressed very slowly. Part of this was due to the nature of meteorites themselves. Nickel-iron meteorites are very difficult to cut open and would have been more so with the equipment available in that era. On top of that, chemical analysis techniques were in their infancy. Still, some discoveries were made, such as the fact that most meteorites come from the same place as asteroids and also the basic classification scheme for meteorites (iron, stony-iron, and stony meteorites) was devised, though this system was later expanded as meteorites were better understood. The pace of discoveries really picked up in the 20th century. In the 1920's V.M. Goldschmidt studied the chemical composition of meteorites as well as other rocks and learned much about how various elements interact geologically, thereby inventing the science of geochemistry and also improving our understanding of Earth and the other solid bodies in the solar system. As a result of research into radiation and radioactive decay in the 1930's and 1940's, scientists found they could use the ratios of various isotopes to date rocks and meteorites. Since most meteorites are thought to have been parts of asteroids which formed very early in the history of the solar system, this offered an estimate as to when the Sun and solar system first formed. Also, 20th century saw the birth of serious meteorite collecting. The man responsible was Harvey Ninninger who started collecting and studying meteorites in the 1930's. He traveled to many different locations just to search for new meteorite discoveries. In the process, he had a number of interesting adventures. One notable example was when he decided to search the Mexican desert. Having heard stories about rampant crime and banditry, Ninninger anticipating the TV series "The A-Team" by a few decades, got hold of an old car and turned into a homemade armored vehicle. However, it was unnecessary since the trip went without incident. Adventures aside, Ninninger's collecting and research advanced meteorite science and eventually inspired commercial meteorite collectors such as Robert Haag. Of course, the stars of this story are the meteorites themselves and they did not disappoint in the last century. In February of 1969, a large number of small meteorites fell on the village of Allende in Mexico. These were no ordinary meteorites, but were of a rare type known as carbonaceous chondrite. They are thought to be relatively unprocessed remnants of the material that helped build the planets and other solid bodies in the solar system. Carbonaceous chondrites had been found before, but they weather very quickly on Earth and are subject to contamination from the surrounding environment. The Allende meteorites were fresh and offered a wealth of information about the chemistry and conditions in the very early solar system. That September in Murchison, Australia, more carbonaceous chrondrites fell, eventually leading to the discovery of amino acids in meteorites (these amino acids are not the result of life, but rather of chemical reactions in the dust cloud which gave birth to the solar system). March of the Meteorites Around that time, Japanese scientists came across the richest hunting ground for meteorites on Earth - Antarctica. This is because meteorites that fall on Antarctica land on and get stuck in ice. As the ice moves, it can bump up against mountains. When this happens, the ice is stuck and is eventually eroded by the wind, exposing the trapped meteorites. And since they are darker than the ice, it is very easy to spot them. In fact, some of the more recent discoveries in meteorite science came from Antarctic meteorites. The Planets Get In On The Act For as long as people have realized that meteorites came from space, it has been thought that they are all chips knocked off asteroids. That's a natural (Continued page 6: Skybox) Skybox (continued from page 5) assumption, and it is true in most cases. However, a few meteorites have been found that do not fit into this picture. A rare class of meteorites known as SNC (Shergottite, Nakhla, and Chassigny - the three meteorites that defined the class) are unusual since they tend to be composed of igneous rocks and are younger than most meteorites. The only asteroid even suspected of having geological activity is Vesta and, even then, it is thought that Vesta went inactive billions of years ago. These meteorites were a puzzle, but in 1983, it was noticed that their composition matched that of one solar system object - Mars. While a Martian origin would solve the mystery of their age and composition, the challenge was to figure out how these meteorites could have left Mars in the first place. It was generally thought that any impact strong enough to accelerate debris to the escape velocity would melt or vaporize the rocks. After numerous computer simulations, this objection was answered. If the impactor came in at a certain angle and velocity, some rocks could be accelerated to the necessary speed without incurring too much damage. And it seems that Mars is not the only place where this happens. A number of meteorites have been found which are similar to some of the rocks brought back by the Apollo missions. These allow scientists to study rocks from regions of the Moon that were never visited by Apollo missions or unmanned Russian sampling probes. So far, no meteorites from Venus or Mercury have been found, but if any can be found, they would be extremely helpful in studying those planets. Back to Freehold As promised, here are my comments on the recent Freehold meteorite and the ensuing media circus. It is quite odd in this day and age when journalists will act as if even a questionable statement from a government official is gospel truth, yet are skeptical over something as obvious as the identity of the Freehold meteorite. It passed all the field tests (evidence that it fell out of the sky, density, and magnetic effects). Yet, they had to wait until several scientists confirmed it. One aspect of the case I found a tad amusing was the police involvement. While I am sure that the Freehold Police Department does a perfectly adequate job of apprehending criminals and clearing the roads of miscreants, I wonder how well equipped they are to deal with a meteorite. As it was, the homeowner had the meteorite temporarily confiscated by the local government. But it was later returned, evidently when the township officials learned that it was a rather mundane nickel-iron meteorite and probably not worth much money. Then there was my small, but interesting involvement in the Freehold meteorite flap as I attempted to bring some order to the rather flippant attitude some mainstream media types had on the matter. On WCTC-AM, Judith Leblein, the regular afternoon drive personality was away on family business (just as well since she has no interest in astronomy at all, despite my repeated efforts) and Alan David Stein was filling in. He said that this incident seemed weird to him and he wondered if the object was doing things like beeping, glowing, or increasing in size, and other "B" science fiction movie clichés. Also, he was not too sure if it was a meteorite. After hearing all his prattle, I knew I had to set him straight. When I got home from work, he was using the meteorite as a way to get into the topic of science fiction movies and he wanted to hear from the audience about which ones they liked. That was when I struck. I called into the program and explained that I liked many science fiction films, but considered "2001" to be at the top. Then, I proceeded to explain how I knew the object in Freehold was a meteorite from the description. When he claimed that it would be impossible to verify meteorites, I told him how nickel-iron meteorites can be verified by exposing the interior, etching with acid and looking for Widmanstatten lines. Of course, I had to explain that the lines are the result of crystallization of iron under microgravity conditions. He didn't question anything I said, but he told me I sounded like every teacher he ever had rolled up into one person and asked if I was a teacher. I told him that I was not, but I was a longtime amateur astronomer and member of AAI. After that, he had to move on to some commercials, but I heard him on the radio asking his producer "How does that guy know all this stuff?" I guess the reason I got to explain as much as I did was that he remembered an earlier call I made to him where I explained that the TV series "Jericho" was a weak rip-off of the 1970's BBC series "Survivors". He had an Internet connection at the studio and verified everything I told him. Perhaps next time I get in touch with him, I'll give him more details of my astronomical background. Meteorites: The Truth is Out There The study of meteorites is a rather interesting branch of astronomy and the only one that offers us amateurs the chance to actually hold pieces of other celestial bodies. While this article is just a brief overview of the history of the field, it may also inspire you to read more about it. Latitude (Continued from page 1) Lincoln, Nebraska is more or less at NJ-latitudes as the swath crosses the Iowa- Missouri and Ne-braska-Kansas borders. As the swath moves further west, across northern Colorado, upper Utah and Ne-vada, before covering Northern California, it also en-compasses Denver, Salt Lake City and Reno. Some-how it failed to impress itself on my awareness that the "Mile High" city of Denver is at the same latitude as a Jersey-eye view. After the vast expanse of the north Pacific, there's northern Japan before crossing into the better part of North Korea. If, during one of their constant power failures, North Korea's Kim Jong-Il took a hankering to look up at the stars one night, he'd have the same sort of juxtaposition of constellations as we do. In an abstract way, there's something intellectually curious about that...well, to me anyway. Next comes the vast territories of northern China, just below their border with Mongolia, including parts of the fabled "silk road" that was an artery of ancient commerce. Then comes a bunch of the so-called "stan" countries, Kyrgyzstan, Tajikistan, Uzbekistan and Turkmenistan. Years ago, they would have all been lumped together and identified as part of the U.S.S.R. Now, their exotic names trip up western tongues who probably know next to nothing about them…unless they have oil reserves. Our NJ-latitude swath crosses much of the oil-rich southern half of the Caspian Sea, the starting point for an oil pipeline meant to bring oil to Europe. On the opposite, western shore, lies Azerbaijan, Armenia, the southernmost tips of Georgia and the northernmost of Iran. Azerbaijan and Armenia are arbitrarily considered to be at the crossroads between Eastern Europe and Southwest Asia. The northernmost borders of troubled Iraq lie roughly another New Jersey length south of the Republic of Georgia. Much of the northern half of Turkey falls under our same skies, including Istanbul and Ankara along with bits of the northern shores of the Black Sea. Continuing further west, we cross the Aegean through the heart of Greece, across the Mediterranean to the heel and sole of Italy's boot - including Naples, but just south of Rome. We don't necessarily consider ourselves to be of a similar latitude as the Mediterranean (particularly in winter!), yet we share the same skies as the northern Mediterranean islands of Sardinia, Minorca and Mallorca. We cross the Prime Meridian just off the Mediterranean, in Spain. Considering our history as a former colony of England, it is sometimes tempting to think of the British Isles as being more due east than they really are. Yet, as this exercise demonstrates, London is over ten degrees north of New Jersey. After passing through Spain (including Madrid) and Portugal, we are once again over the vastness of an ocean, the North Atlantic. This time, however, the monotonous water is briefly broken up by our NJ swath encompassing the northernmost two islands of the Azores, tiny Corvo and the larger Flores. Belonging to Portugal, they were first bumped into in 1427 by one of the captains sailing for Henry the Navigator, possibly Gonçalo Velho, though this isn't certain. Some 3,900 miles later, and we're almost home. Our swath also takes in New York's Staten Island, Long Island and Manhattan, as well as the lower bits of Connecticut before we're back in New Jersey again. While perhaps not completely an astronomical exercise, such considerations test the geographic self-image we carry in our heads. After all, did you really know that the arrangement of the night sky you will see tonight is the same as that seen by the people of southern Italy, North Korea or a tiny island in the Azores? Stunning Beauties of Our Solar System by Ken Kremer Rosetta Swings by Mars for an Astronauts Eye View On 25 February 2007, the ESA Rosetta comet chasing mission flew by Mars to within 150 miles of the surface of the red planet. That's closer than the 3 science surveying spacecraft currently orbiting Mars from NASA and ESA (the European Space Agency). The main goal of this flyby (and three future flybys of Earth) is to hit the exact aim point required to target Rosetta on course for its long, circuitous trek through the inner solar system and the asteroid belt to reach Comet 67P Churyumov-Gerasimenko. Rosetta will rendezvous with and even-tually orbit the comet in 2014. The spacecraft is comprised of 2 parts, the Rosetta mother ship and a first of its kind comet lander, dubbed "Philae". Together, they will conduct the first long term science observations and landing on a comet nucleus. Rosetta was launched on 2 March 2004 by an Ariane-5G rocket from Kourou, French Guiana. See the rest of this pictorial supplement at www.asterism.org Click Newsletter. Please contact me for further information or public outreach presentations. My next public talks are: " Raritan Valley Community College Planetarium: Somerville, NJ, Tue Mar 27, 7:30 PM. "Touring Our New Solar System (in 3-D)". http://www.raritanval.edu/planetarium/" Rittenhouse Astronomical Society (RAS) in the Franklin Institute: Philadelphia, PA, Wed Apr 11, 8 PM. "Mars, Saturn, Comets and Beyond (in 3-D)". http://www.rittenhouseastronomicalsociety.org/" The Explorers Club, NY, NY, Mon Apr 23, 7 PM. "Exploring Mars, the Search for Life and a Journey in 3-D". http://www.explorers.org/index.php Dr. Ken Kremer, NASA JPL Solar System Ambassador, Email: kremerken@yahoo.com Letter From Dr. Lew Referring to the article on Double Star observation in the February Asterism, great work Clif Ashcraft. It was a pleasure to read a good research paper and about all the effort involved. As you stated, the only way to measure the masses of the components of a visual binary is through observation. I would like to give a simplified version of how this is done. From the measured separation of the compo-nents we have in seconds of arc. The component separation in astronomical units is therefore S = rP (1) where rP = the distance to the binary in parsecs. No S is not the semimajor axis, a, of the ellipses but with sufficient observations a method has been developed for determining a (See Celestial Mechan-ics and Astronomical Mathematics for Amateur As-tronomers, page 235 available in the AAI Library or at the Sales and Promotions Counter). The total mass, mT, of the system is given by Ke-pler's Law modified by Newton which is mT = a3/P2 (2) where P = the orbital period in years Spectroscopically one can determine the veloci-ties of the components relative to their barycenter as vAC and vBC. These are in inverse proportion to the masses mA and mB so that mB = mT/(1+vBC/vAC) and mA = mT mB (3) The relationships of binary objects is mALA = mBLB (4) LA + LB = a (5) where LA, LB = the respective distances of each com-ponent from their barycenter Knowing mA and mB gives us LA /LB= mB/mA and from (5) one easily calculates both LA and LB Thus we have found the masses of each compo-nent and their respective distances from their bary-center. MEMBERSHIP DUES Regular Membership: $21 Sustaining Membership: $31 Sponsoring Membership: $46 Family Membership: $5 Sky & Telescope: $32.95 Astronomy subscription: $34 First Time Application Fee: $3 Dues can be paid in person to Mem-bership Chair or Treasurer, or by mail to: AAI, PO Box 111, Garwood, NJ 07027-0111 DR. LEW'S SEMINARS Some of the topics for upcoming seminars include: " What is the frequency of solar and lunar eclipses and what de-termines this? " In the BCs, how did the May-ans forecast eclipses? " Rotation of the Milky Way. FRIDAYS AT SPERRY March 23, 2007 Reaching to Some Great World: the Exploration of 4 Vesta Al Witzgall March 30, 2007 Video April 6, 2007 Optics 2: Interference and, Dif- fraction Dr. Lew Thomas April 13, 2007 Astronomy on the Thames: Slouching Towards Greenwich Kathleen Quinn Vaccari DOME DUTY SCHEDULE Apr. 6 Team D Apr. 13 Team E Apr. 20 Team A Apr. 27 Team B May. 4 Team C EMAIL CONTACTS editor@asterism.org Editor of The Asterism Ray Shapp, Acting Editor Deadline for submissions to each month's newsletter is the first Friday of that month. membership@asterism.org AAI Membership Chair trustees@asterism.org All three Trustees of AAI ray@asterism.org Ray Shapp for the website exec@asterism.org Executive Committee All schedules above were accurate at time of publication. Please check www.asterism.org for latest informa-tion (click on "Club Activities") (Choice of topic at Dr. Lew's seminars is determined by participants' interest) Theater In The Sky by Ron Ruemmler April 2007 is more interesting than average without anything really spectacular occurring. The major planets are nicely spread out from dusk to dawn, so there's always something nice to look at, but you may not have much choice. Every evening's viewing has to start with Venus just after sunset. The brilliant "Evening Star" doesn't set until more than three hours after the Sun. This translates to around 11:00 PM thanks to Daylight Saving Time. Venus moves through the shoulders of Taurus, the Bull, this month. Watch the planet zip below the Pleiades star cluster during the second week of April. Saturn starts each night high in the southeast and sets about three hours before dawn. The Ringed Planet has lost almost half a magnitude of brightness in the last two months as its rings begin to flatten out, but it is still brighter than it will be for the next seven years. Jupiter rises around midnight and, at the very end of the month, might be visible before Venus sets. Mars still rises about an hour before morning twilight as it has since the end of last year. The Red Planet is just starting to brighten and move away from the Sun as it prepares for a lovely opposition in December. Mercury is hopelessly close to the Sun all month. Over the full year, all the planets spend most of their time moving eastward, to the left, with respect to the stars. However, for a few months each year they move backward, to the right. This retrograde period can be interesting if a bright star is nearby. For the outer planets, retrograde motion always begins in the morning sky. Jupiter starts that this month as it moves back toward Antares, the heart of Scorpius, the Scorpion, which it passed in January. It will reach a point north of the star in August when the planet will resume direct motion. The end of retrograde motion for outer planets always happens in the evening. This month Saturn reaches this so-called stationary position. Ever since Christmas, Saturn has been moving to the west, away from Regulus, the heart of Leo, the Lion, which is now off to its left. The planet will pass less than one de-gree from the star in September when they, unfortunately, will be invisibly close to the Sun. The distance between Saturn and Regulus this month is almost twelve degrees, which happens to be how far the Moon appears to move in a 24-hour period. From northwestern Canada the Moon will actually cover Saturn on the evening of the 25th and then Regulus 23 hours later. April SKY CALENDAR 2 Mon 1:15 PM Full Moon 5 Thu 9:00 PM Jupiter begins retrograde motion back toward Antares 8 Sun First Sunday after the first Full Moon of Spring, hence, Easter 8 Sun 5:30 AM Moon below Jupiter 10 Tue 2:04 PM Last Quarter Moon 11 Wed 8:30 PM Venus lower left of Pleiades star cluster 13 Fri 5:30 AM Mars lower left of crescent Moon 14 Sat 5:30 AM Mars upper right of crescent Moon 17 Tue 2:00 AM Moon at perigee, closest to the Earth 17 Tue 7:36 AM New Moon just after perigee; expect extreme tides 19 Thu 8:30 PM Crescent Moon between Venus and Pleiades 21 Sat Astronomy Day! Many observatories open to the public 22 Sun 8:30 PM Crescent Moon directly below Castor and Pollux 24 Tue 2:35 AM First Quarter Moon 24 Tue 8:30 PM Saturn lower left of Moon; occultation visible from NW Canada 25 Wed 8:30 PM Regulus lower left of Moon; occulta-tion visible from NW Canada Stunning Beauties of Our Solar System by Ken Kremer Pictorial Supplement In this golden age of space exploration, February 2007 was a very special month with a remarkable series of celestial encounters. Three flyby's occurred within 7 days: Cassini flew by Titan on Feb 22, Rosetta swung past Mars on Feb 25 and New Horizons rocketed past Jupiter on Feb 28. All designed as essential gateways to enable more stunning science in the near and distant future. Here for your enjoyment is this month's small sampling of beauties, rich in visual beauty and previously undiscovered science that caught my attention from NASA and ESA in my role as a NASA Solar System Ambassador. Polar Clouds over Annotated Mars in True Color from Rosetta Credit: ESA © 2007 MPS for OSIRIS Team MPS/UPD/ LAM/IAA/ RSSD/ INTA/ UPM/ DASP/ IDA http://www.esa.int/images/AnnotatedNACT_H.jpg Text free version: http://www.esa.int/images/MarsNACTrueColor_square_2_H.JPG See a cool animation of Phobos transiting across the Martian disk and Mars as seen from Rosetta in 3- D here: http://www.esa.int/esaMI/Rosetta/SEM9R6N0LYE_0.html Pictorial Supplement (continued) by Ken Kremer STEREO's Stunning Behind: Moon Transiting Sun A stunning movie animation of the eclipse and solar active regions can be downloaded from the STEREO website: http://stereo.gsfc.nasa.gov/index.shtml Photo Credit: STEREO/NASA http://stereo.gsfc.nasa.gov/gallery/stereoimages/preview/preview_transit.shtml Pictorial Supplement (continued) by Ken Kremer Islands Inside the Great Lakes of Titan The Cassini orbiter returned new radar and visible light data from the close flyby of Titan over the high northern latitudes on 22 Feb 2007 and revealed a giant new lake over 100,000 square kilometers in size. That's larger than Lake Superior. A vast 90 km wide island was discovered in the middle of the lake, located near the north pole of Titan (see radar image below) at 79 degrees North. These lakes are not merely pure meth-ane, but are also comprised of ethane and more complex organic molecules according to Dr. Jonathan Lunine, who gave a lecture on the discovery of Titan's lakes in Princeton, New Jersey a few days after this radar image was taken. Dr. Lunine, a Cassini science team member from the University of Arizona, speculated that ammo-nia may also be a significant constituent of the lakes. Ammonia would cause the lakes to freeze at a lower temperature. Pictorial Supplement (continued) by Ken Kremer Spectacular Volcanic Plumes At Io As New Horizons Rockets Into the Unknown ! The first NASA mission to the planet Pluto, rocketed past Jupiter on 28 Feb 2007 for a gravity assisted flyby to increase the spacecraft speed by about 9,000 MPH (half the speed of the Space Shuttle). This maneuver will cut the travel time by 3 years. Top priority was to precisely hit the Pluto aim point, just 500 miles wide at a dis-tance of 500 million miles from Earth. This was accomplished, and over 700 science observations were suc-cessfully completed. The data will be streaming back over the next few months while the ship records another first -- flying through the magnetotail of Jupiter.