Volume XVIII No. 4 January 2007 gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg Astronomers and the History of Photography By Gordon Bond As some of you already know, I also have an active interest in history - I've even bored some of you by prattling on about some of the projects I'm involved in (www.commonbondhistorians.com). I've been working on creating presentations I can give on various subjects to local historical groups, including one on how the advent of roll film allowed affordable and compact cameras in the early 1900s. The result was nothing short of the "democratization" of photography as it came within the reach of the average person. In the course of delving through various sources on the history of photography, one encounters scientists, artists, social reformers, explorers and more. As might be expected, chemists are well-represented. But, as should be equally expected, a few astronomers also have made significant contributions. This shouldn't be all that surprising. After all, astronomers deal with optics and the manipulation of light as part of their stock and trade. Yet the connection goes back to pre-telescopic times. al-Haytham, Kepler and the Camera Obscura Traditional, photographic cameras (as opposed to digital) are really just layers of improvements built around the very simple principle of the "pinhole" camera. It was known since antiquity that a small hole - a pinhole - in the wall of a completely darkened room would cause an image of whatever was outside to be projected (http://tinyurl.com/y44gcf). Among the earliest of those to study this was an Arab scholar, Ibn al-Haytham (also Alhuzen'; 965-c.1040 AD), who was born in Basra, Persia, but made his name in Cairo (http://tinyurl.com/yb29zb). al-Haytham's scientific pursuits were many and varied, ranging from mathematics and physics to medicine and astronomy. But his strong suit was optics - not in the modern sense involving manmade lenses, but speculating on the nature of light and how it is manipulated in the natural world. He proposed theories to explain everything from shadows to eclipses to rainbows. He even correctly explained the optical illusion of the Moon or Sun seeming to be larger when near the horizon. What he would be most remembered for, however, were his experiments into understanding vision and the structure of the eye. Where previous thinkers as lofty as Euclid and Ptolemy held that vision was a product of rays of light somehow emanating out of the eye, al- Haytham realized it was, in reality, the reverse. He had used experimentation to test his ideas - a novel approach for the time - rather than rely on past authorities. Among the tools he used, was a pinhole camera. He expounded his mathematical theory of vision in a lengthy book called, Optics. Latin translations found their way into Europe, and into the hands of Johannes Kepler. (Continued on page 2: Photography) Photography (continued from page 1) By Gordon Bond Kepler (1571-1630) is a name that will likely be well-recognized by readers of The Asterism! But what some may not know, however, is that he was the one who first coined the other commonly used term for the pinhole camera - "camera obscura" - which is Latin for "dark chamber." The very word, "camera," can trace its roots to this usage. Further, his interest in optics led him to suggest that it might be improved upon by adding a lens in place of the pinhole. He used a camera obscura to view the transit of Mercury in 1607 and would apply his knowledge of optics to discover the counterintuitive fact that the lens of the human eye projects an inverted image onto the retina, which the brain has evolved to flip right side up to deal with. We may remember Kepler primarily for his three laws of planetary motion, but he should also be recognized for this optical work that would influence the birth of photography (http://www.bbc.co.uk/dna/h2g2/A2875430). Arago, Herschel and the "Art of Photography" Some readers may be familiar with "daguerreotypes" and even have some in old family albums. The term is derived from the name of the French artist and chemist recognized as the inventor of the process, Louis-Jacques-Mande Daguerre (1787-1851) (http://tinyurl.com/ub67u). With a daguerreotype, the image is exposed directly onto a mirror-polished surface of silver that's been coated with silver halide particles deposited by iodine vapor. Bromine and chlorine vapors were later used to reduce exposure times. The image is a "direct positive" and is, effectively, a "one-of-a-kind" image, since there is no negative to make further reproductions. Samuel Morse (of telegraph fame) introduced the process to America and it's novelty caught on immediately. Daguerreotype portrait studios sprang up across the U.S. in the early 1840s. A young Matthew Brady learned the process in New York, helping to launch his lifelong career. Studios churned out images of varying quality of everything from the common folk to portraits reflecting a "whose-who" of mid- 19th century culture to the world's first erotic photos. What many people don't know, however, is that the money to bankroll the promotion of Daguerre's invention came from a French physicist who was the Director of the Paris Observatory. Francois Arago (1786-1853) was known for coming up with many of the observatory's optical instruments, and he served as secretary of France's Academy of Sciences (http://tinyurl.com/uerjq). So he had a true appreciation of the science behind Daguerre's work. But he also keenly appreciated the economic aspects as well. In addition to his scientific career, Arago was also a well-connected politician and he was able to use his influence to secure the funding and generate the publicity that would make Daguerre's process so successful. There is, however, a slightly dark side to this story. Arago seems to have known that another man, Hippolyte Bayard (1807-1887), had actually come up with the process first (http://tinyurl.com/y5g5pw). Indeed, a few scientists and dabblers had discovered variations of the concept to differing degrees. But as early as June 24, 1839, Bayard had an exhibition of his photographs, proving he had hit upon an established method of creating and fixing images. Daguerre had announced his process in January, but the details were not forthcoming until August - after Bayard had already had a showing! Arago must have been sensible of the threat this priority (Continued page 7: Photography) Stunning Beauties of Our Solar System By Ken Kremer Three Years of Sunsets on Mars Both rovers continue their science treks across the Martian surface and are celebrating three years of continuous exploration on January 3 for "Spirit" and January 24 for "Opportunity". That's more than a thousand Martian days (Sols) for each rover. Twilight lasts longer on Mars, compared to Earth, due to the scattering of sunlight to the night side of Mars by the abundant high altitude dust. The high altitude red color at sunset and sunrise is caused by light scattering off the red dust, whereas nearer the horizon, the light scattered is bluer, a reversal of the colors seen on earth. All rover color photos are in fact "approximate true color". They are obtained by combining separate raw images taken with red, blue, and green filters based on a mathematical distribution and also comparing to the on-board color calibration target and pre-flight calibration. (Continued page 11: Stunning Beauties) First Light at Chiefland Astronomy Village by Ernie Rossi I have been an active observer for many years, doing most of my observing in the Northeast. I've observed from the dark sites of New Jersey, Cherry Springs in Pennsylvania, Stellafane in Vermont, in central Maine as well as in my own dark- site home located just west of the Catskill Mountains. I've also observed for two nights at the astronomy village of New Mexico Skies. I had read some articles about Chiefland Astronomy Village (CAV) and always thought that I would want to visit someday. As it happens, our retirement community in central Florida is just 95 miles from CAV. Joe Mize, one of the best astro-photographers around, lives in CAV. I contracted him because I own some large Dobsonian telescopes, and I wanted to add a drive system to possibly two of them because even with large eyepieces having 82-degree fields of view, objects move across the field pretty quickly, and minute detail can be missed. I also decided that I wanted to add a good video camera to view fainter detail than was possible visually. Looking into equatorial platforms and other drive systems, I decided on the Servo Cat go-to tracking system with remote. Joe Mize has the expertise to do the installation and to calibrate the drive. When I emailed Joe and told him about what I wanted to do, Joe told me about Mike Zamitt who builds the Star Structure Telescopes. Mike has experience on the Servo Cat installations and he installs this unit on his 'scopes. I contacted Mike, and placed the order to do the 20-inch scope first. My 20-inch Obsession f/5 is 100 inches in height, and it usually requires a ladder to reach the eyepiece. Once all the parts arrived, I took the rocker box assembly (without mirror) down to Mike's shop in Holiday, Florida, A week later, I brought down the rest of the 'scope so we could check it out for accuracy, but it was overcast that day. Instead, I agreed to meet him at CAV because he was bringing up a new 'scope to a client for testing. There he could show me how the 'scope worked and how to calibrate the movement, if needed. Friday, October 20, 2006, I arrived around 3:00pm to set up my 'scope hoping to do some observing and to check out the skies. CAV is located in northwest Florida about 20 miles inland from Cedar Key, just south of the Florida panhandle. The only town close by is Chiefland, about 7 miles away. Members who live at CAV abide by very strict rules, and Chiefland has some strict ordinances on lighting, but nothing is perfect. Ocala is 40 miles away, and Orlando is about 125 miles. CAV consists mostly of manufactured homes of various sizes with separate roll-off sheds that measure from 12 to 24 feet, many of which house the owners' high-quality 'scopes. Most of the homes are on five- acre tracts. Tom Clark and his wife, Jeannie, live at CAV and own the grounds the observing field is on. Tom has many telescopes and is the former manufacturer of Tectron telescopes. Tom probably has one of the largest private telescopes in the country -- a 42-inch 1700 pound monster which he keeps in a regular observatory. Tom has built a very large and impressive private workshop next to his house. The observing field is very large and flat with low grass and several structures. There are showers, bathrooms, a refrigerator, microwave, coffee pots, electric outlets for RVs, and 'scopes are situated throughout the field. There is also a large picnic area with charcoal grills available if you want to do your own cooking. The facility is kept in top condition and it is extremely clean. Friday was a warmer and more humid than usual with temperatures around 90 degrees. I didn't think the transparency would be very good because the sky looked hazy. The field was dominated by Star Structure Telescopes including 12.5, 16, 20, and a 28-inch f4.3. I saw other high-quality 'scopes such as Star Masters up to 22 inches and several 6-inch Astro-Physics on 1200 mounts, a 12-inch LX 200, and a 10-inch Takahashi MT 250 -- all top-quality telescopes. John Novak who was featured in issue 52 of Amateur Astronomy was there with a beautiful 6-inch Astro-Physics. He has 24-inch and 36-inch Ritchey- Chretiens in his observatory. Amazingly, it cleared, and I could see the Milky Way even before it got dark. Talking to the observers who frequent CAV, everyone was in agreement that this was no more than an average night with soft transparency, However, the seeing was very steady. By 8pm, the temperature was about 75 degrees, and at 4am, when the clouds rolled in, it was still about 65- 70 degrees. All I had on the entire night was a short sleeved shirt. The exact day, two years earlier at my place in the Catskills, I was observing with two inches of snow under my feet dressed like an Eskimo climbing up an icy ladder with temperatures in the 20s. The only part of the sky that wasn't very good was to the north where the town of Chiefland is located. I estimate visual magnitude 5.0-5.2 with a light dome protruding about 10 degrees above the horizon. Even (continued next page) so, the Milky Way looked very good, very bright with black rifts running through it and extending from horizon to horizon. Estimation of visual magnitude at zenith was 6.0 to 6.2; under pristine conditions it could have gone to 6.5 magnitude or slightly better. I felt the transparency under average conditions was on a par with or slightly less than Deposit, New York but not as good as Cherry Springs. What it did have was very good seeing; there was no turbulence so you could really push the magnification to darken the sky. Globular clusters just looked fantastic like M22, M15, M13, open clusters NGC 7789, 663, 884, 869, even galaxies and planetaries since high magnification was no problem. Most of the night I was using 284 x and even went as high as 564 x on the Trapezium. Stars didn't bloat or shimmer, just pinpoints of light looking like high-end refractor images. This was the first time I ever saw the Trapezium G star (which is 15+ magnitude) in my 20-inch. Holding the object steady with the drive system makes a big difference. Once before, under a good transparent Catskill mountain night using my 25-inch, I did get the opportunity to see both G and H stars within the Trapezium. It was a pleasure to take out an eyepiece, go down the ladder and get a high magnification eyepiece, put it in the focuser, and find the object still there. For the first time I got to see the Horse Head nebula through Margie Wright's 16-inch Star Structure telescope which was set up next to mine. This wouldn't be possible without a good drive system and steady seeing. We didn't use a filter. This was Margie's first large scope, and she was just overjoyed by the images this scope was delivering. Another object NGC 7009, the Saturn nebula, was the best I've seen with the 20-inch because of the steady sky, high magnification, and drive system -- absolutely wonderful. The blue- green color just stood out, and the extensions really looked like a ring going around it. At 284 x this planetary just stood motionless in the eyepiece. At 564 x the E and F stars in the Trapezium were just pinpoints and were laughingly separated so far from the bright stars, which were again not bloated but bright pinpoints. Comet Swan showed a tail not very long, but easy to see in a 10-inch Maksutov Cassegrain. I took some time away from my 'scope to check out others, including a 28-inch Star Structure owned by Scott Brunetti while it was set on M22 -- just great detail, and the stars were so bright! Other seasoned observers at Chiefland that evening (and if I miss you I'm sorry) were John Gurtis, Roal Leon who sketches wonderful drawings at the eyepiece, Steve Bruner with his 20- inch f4/3 Star Structure (I would have liked to compare my 20-inch Obsession images with his) John O'Neill with his 10-inch MT 250 with whom I had breakfast at Chiefland, Rick Donnelly who I believe had a 12-inch LX200, and Dave Gracey with his 18-inch Starmaster. I was told they expected lots of dew because of the hot day and the temperature drop but dew heaters and fans were optional. Just before the clouds rolled in around 3:30am, I had a quick look at Saturn low in the east, and again the image was rock steady. I can't wait until early next year to view Saturn near opposition at zenith. I packed it in around 4am, covered my 'scope, slept for a few hours before breakfast in Chiefland, and then I went home. I seemed to have more energy while not dressed for winter and fighting the cold. The tracking system also saved lots of trips up and down the ladder. I had a wonderful time observing, and everyone was extremely nice and very knowledgeable. I loved the steady sky conditions, flat field, with good horizons, all the amenities, and the warm climate. I was worried when I came to Florida that I might not find a good observing location, but now that worry is gone. I am looking forward to the CAV star party that starts November 15. Clearing the Neighborhood by Jeremy P. Carlo In my Friday night talk on November 10, 2006, I discussed the status of Pluto as a result of the August 2006 IAU meeting in Prague, where it was decided that a planet shall be a body that satisfies three criteria: (1) Is in orbit around the Sun; (2) Has sufficient mass so as to have a shape determined by hydrostatic equilibrium (i.e. round); (3) Has cleared the neighborhood around its orbit. As a result of this new definition, 8 of our 9 "classical" planets keep their planetary status, while Pluto is shifted to the new category of "dwarf planet," along with fellow exurbanite Eris (formerly known as "Xena" and 2003 UB313), and the largest asteroid, Ceres. The discovery of Eris was in fact one of the principal stimuli for this meeting, as Eris is slightly larger than Pluto; if Pluto is a planet then it's fair to state that Eris also is (as well as any similar objects yet to be discovered). Criterion (1) eliminates moons from consideration. As it is currently written, (1) also eliminates extrasolar planets (which could be included by replacing the word "Sun" with the word "star" in the definition), and any rogue planets floating through space without a stellar parent. Criterion (2) effectively sets a minimum size on putative planets. While it may seem simpler to set some minimum mass or radius and be done with it, any such convention will be arbitrary. 500 miles? 500 kilometers? A million cubits? As I said in my talk, getting astronomers to agree on such an arbitrary standard is like herding cats. But as I showed in the talk, as you add more and more mass to an object, its tendency is to become spheroidal in shape, as gravity increasingly dominates the short-range intermolecular forces. Thus sphericity is an excellent test of whether an object is dominated by these short-range intermolecular forces (such as your average terrestrial rock or small asteroid), or dominated by long-range gravitational forces. In addition, gravitational domination leads to stratification of layers - core, mantle and crust; this makes possible vulcanism, plate tectonics, a dynamo-generated magnetic field and other geologically interesting phenomena. Finally, sphericity assures a uniform distribution of gravitational field strength on the surface, and combined with relatively rapid rotation, yields a moderate temperature distribution, which helps the putative planet hold on to an atmosphere and perhaps liquid water, both precursors for life. Therefore, criteria (1) and (2) are relatively well- accepted. In fact, a definition consisting essentially of (1) and (2) was proposed at the IAU meeting, which would have preserved the nine existing planets, and added Ceres (the only asteroid big enough to be unambiguously spherical), Pluto's moon Charon , and the distant Eris. However, this proposal was ultimately voted down and replaced by one including criterion (3). Once the proposal was accepted, the situation comes down to deciding what it means for a planet to have "cleared its neighbourhood." In an absolute sense, no planet has done so. Earth passes through debris left by numerous comets (which cause meteor showers as the Earth "clears its neighbourhood"; this fact was pointed out to me by a 9-year old boy at a similar talk I gave at Jenny Jump in September). Even kingly Jupiter follows and is trailed by Trojan asteroids which hover in the L4 and L5 Lagrangian points of its orbit. Neptune's orbit is peppered by Neptune Trojans and by Pluto and its Kuiper Belt Object (KBO) kin. So no planet has truly cleared its neighborhood of all debris. Earth has its Earth-crossing asteroids (most famously 433 Eros), and Mars has a set of its own. Clearing the neighborhood is a work in progress, at best. But the answer becomes clear if we try to analyze the situation quantitatively. Photography (continued from page 2) By Gordon Bond presented to the patents of - and potential profits from -the man he had been backing. He would actively encourage Bayard to delay announcing his discoveries, allowing Daguerre to stake his claim as the prime inventor of photography. One who was watching these developments with keen interest was a man who bore a name made famous in the world of astronomy. Sir John Frederick William Herschel (1792-1871) was the son of the distinguished William Herschel and an accomplished astronomer in his own right. Like the others, he too became enamored of the idea of capturing and fixing an image. In 1839, he had success creating a picture on glass using hyposulphate of soda. His choice of subject? His late father's famed telescope at Slough, England! Though the image is a murky silhouette, some detail can be divined digitally and this was certainly the first time a telescope had been so recorded for posterity. On March 14, 1839, Herschel presented a paper to the Royal Society entitled, "Note on the art of Photography, or The Application of the Chemical Rays of Light to the Purpose of Pictorial Representation." This was a landmark paper for a few reasons, not the least of which being its title contained the first use of the term "photography." It was also the first time the words "positive" and "negative" were used in the photographic context and he even coined the descriptive term "snap-shot." Herschel was responsible for establishing the basic vocabulary of photography that we still use today (http://tinyurl.com/va3cs). de la Rue and the Photoheliograph There is a wonderful image Daguerre made in 1839 that looks down over a tree-lined Parisian boulevard and street corner. The streets seem deserted. All except for a tiny silhouette of a man on the corner, who paused to have his shoes shined, just long enough for his shape to be burned into Daguerre's emulsion. Anonymous and tiny, through sheer dumb luck, the figures of the man and shoeshine boy may very well be the first humans to have ever been photographed. But it's the empty streets that are telling. In all likelihood, they were really bustling with pedestrians and horse-drawn carts. They escaped detection because of how slow such early emulsions were to record an image. The same low "speed" of the film that made some early photographers believe it was impossible to photograph anything in motion, also rendered recording the dim objects astronomers saw through their telescopes impractical. Other scientists were quick to grasp the potential of photography to faithfully record the objects of their study, but astronomers had a disadvantage. Nevertheless, there were those who eagerly pushed the technology to remarkable results. The study of what we would call today "deep sky" objects wasn't really well-established in those early days. Instead, astronomers focused their instruments and attentions on the solar system. This was fortunate in that there's no brighter astronomical targets for photography than the Sun and Moon! Warren de la Rue (1815-1889) began his career in his father's stationery shop in Guernsey, England, but even then showed an aptitude for science and engineering. He even invented a machine to make envelopes! He went to study in Paris before returning to the family business and maintained an active interest in astronomy, microscopy and chemistry in his spare time. He published papers on a wide range of subjects, including electric discharge in gaseous substances and inventing the silver chloride battery cell. His interests in photoactive chemicals, however, led him to adapt the wet-plate process to make incredibly high quality pictures of the Moon in the 1850s, the detail of which made them the standard for years after. This initial success inspired de la Rue to establish a new observatory in England at Cranford (of all places!), Middlesex. He attracted the attention of Kew Observatory, who, in 1854, approached him to design a telescope-camera contraption to allow daily photographic records to be made of the Sun - something John Herschel had proposed earlier. The result was the first "photoheliograph" (http://tinyurl.com/yxf7dg). With the efforts of people like de la Rue, astrophotography emerged as its own, separate discipline. Thought not strictly "astronomers" per se, opticians and physicists have also played critical roles in photography's evolution. John Benjamin Dancer (1812-1887), for example, described himself as "Optician, of Manchester, by appointment to HRH the Prince of Wales." Dancer produced early projectors and coined the term "lime-light." He manufactured cheap microscopes and took some of the first microphotographs. In 1840, he photographed a flea using a gas-illuminated microscope. Stereo images were known, but made by taking a picture, moving the camera a little (continued page 10: Photography) Stewart's Skybox By Stewart Meyers Since this article is appearing in the January 2006 Asterism, I thought I would touch on something never before discussed in this column. For thousands of years, people honored the winter solstice. Even the date for the Christmas holiday was chosen by the early church leaders to capitalize on these celebrations to make it easier to convert non- Christians. So, there is a long tradition of celebrating the Sun at this time of year and the Sun is the subject of this column. AN INNOCENT SUN? Recently, the results of a study by Peter Foukal of Heliophysics, Inc. were published in Nature (http://www.nature.com/nature/journal/v443/n7108/abs/nature05072.html), and seemed to indicate that variations in solar luminosity were not sufficient to cause climate change. This news received considerable notice in the media with people such as Michio Kaku loudly trumpeting the report, though they were likely more interested in it for the political aspects as opposed to scientific ones. But, other recent (and less heralded) studies show that Foukal may have been looking at the wrong thing. AN INCONSTANT SUN Before examining the studies in detail, it is a good idea to discuss the history of the solar variability in general. Prior to the 1600's, it was widely believed in the Western world that the Sun was unchanging (the Chinese court astrologers occasionally saw sunspots when the Sun was either heavily reddened at sunset on hazy days or when the Sun was dimmed by clouds, but these observations were never published outside of the royal archives). This was quite a natural assumption since anyone foolish enough to directly stare at and study the Sun wound up with severe burns to their retina (something that still holds true today). Then, late in 1610, Galileo pointed his telescope towards the Sun. His early attempts at solar observation most likely damaged his eyesight and were probably a major factor in his later blindness. Soon he noticed little black dots on the Sun. These would move across the disk over the course of two weeks. Another observer, Galileo's Jesuit rival, Christopher Scheiner also made similar observations. The fact that he had a rival was probably what prompted Galileo to publish the observations (and get into some trouble). Eventually these spots were accepted, but no one really gave them much attention. Though in 1825, one man did. A NON-VICIOUS CYCLE Heinrich Schwabe was an apothecary (what we would call a pharmacist today) in Dessau, Germany. At the time, people were speculating as to whether or not the planet Vulcan existed. No, this was not the arid, Earth-like planet in orbit around 40 Eridani A which is home to a highly logical, pointy- eared, green-blooded species from the "Star Trek" franchise. This planet Vulcan was a hypothetical planet that was thought to orbit closer to the Sun than Mercury. Schwabe thought that discovering Vulcan would be the path to fame and fortune, so he set out to observe the Sun on every clear day in the hopes of seeing Vulcan transit the Sun. However, he soon found the spots on the Sun to be rather fascinating and eventually forgot all about Vulcan and concentrated on studying them. After twelve years of observation, Schwabe concluded that the spots were not random, and that their numbers appeared to rise and fall in a cycle. He published his results and continued observing. In 1843, he felt he had enough data to confirm the presence of a cycle. Initially, it was thought to be a ten year cycle, but it was later found to be roughly an eleven year cycle. Once the idea of the cycle was established, astronomers started to pay serious attention to sunspots. Since they did behave in a non-random fashion, it was thought they could tell something about what was going on with the Sun. But it would be some time before any progress was made. A MAGNETIC ATTRACTION In 1908, George Ellery Hale (the man the 200-inch telescope is named after) used the then-new science of spectroscopy to determine that sunspots had something to do with magnetic fields. With this discovery, scientific study of sunspots, solar activity, and eventually the solar magnetic field could begin. But, for the purposes of the story, we have to backtrack a little. TAKING IT TO THE MINIMUM In 1893, Edward Maunder was looking over historic records of sunspot observations. He noticed that, from about 1640 to 1715, hardly anyone reported seeing sunspots. At first, it was thought that it was a case of astronomy losing interest after the (continued next page) novelty of sunspots wore off. But, it appeared from the accounts of what few spots were observed, that this was not the case. Astronomers were indeed still looking. Then Maunder noted that this period coincided almost perfectly with a stretch of time referred to as "The Little Ice Age" where winters were very cold. Maunder thought this was more than mere coincidence. Later scientists were skeptical and still thought that this was the case of an incomplete record. Fortunately, there is another indicator of solar activity that always caught the attention of observers, especially in the days before outdoor lighting. The aurora borealis or northern lights are caused by charged particles from the Sun dumping their energy via the Earth's magnetic field into the upper atmosphere. This causes the gases there to glow, usually in colors ranging from red to green. During the Little Ice Age, aurora sightings dwindled considerably. This proved that the sunspot shortfall was real. And the period of time is referred to as the "Maunder Minimum" in honor of the man who found it. In the years since, other such periods have been found, including one that started in the early 1400's and coincided with a climactic downturn that doomed the Viking settlement in Greenland and almost wiped out the Iceland settlements as well. The idea that somehow changes on the Sun can affect Earth became acceptable to discuss. At first, it was thought that the reason the weather was cooler during these minima was that the Sun was emitting less light because of the reduced number of solar flares. This seemed plausible, but hard to investigate since most of the instruments that could measure the Sun's output were on the ground beneath the variable atmosphere. Fortunately, with the Space Age, it was possible to launch probes to study the Sun from space. Even weather satellites were equipped with instruments to monitor the Sun. Of course, scientists like to have another way to measure the Sun's activity as a backup. One of the aspects of the Sun's magnetic field is that it envelops the solar system and greatly reduces the number of cosmic rays reaching Earth. When cosmic rays do reach the planet, some of them hit carbon atoms and turn them into carbon-14, the unstable isotope of carbon used for dating purposes. Another cosmic ray-related isotope is beryllium-10. By studying the levels of these isotopes in various substances of known ages, it is possible to roughly reconstruct the level of solar activity at a given time in the past. Essentially, how it worked was that the higher the amount of carbon-14 and beryllium-10, the more cosmic rays reached Earth due to the lower level of solar activity. All this would normally be of interest mainly to scientists studying the behavior of the Sun as well as those concerned with the processes going on in stars in general. However, with the controversy of global warming and what influences it, the study of the role of the Sun in climate variations has taken on an almost political nature, with some scientists stating that the Sun is a significant factor and others who feel its influence can be ignored. Then, in late 2006, Peter Foukal came out with his study. Armed with sunspot and solar activity data as well as solar luminosity measurements by satellites over the course of several solar cycles, Foukal concluded that any variations in the Sun's luminosity had almost no effect on climate at all. This seemed to rule out the Sun as having any real influence on climactic change. But, it seems Foukal was overlooking one small thing, actually millions of very small things. MILLIONS OF LITTLE PARTICLES Back in 1997, it occurred to Henrik Svensmark of the Danish National Space Center (http://www.dsri.dk/) that nobody ever considered whether high-energy cosmic rays might have any effect on the Earth's atmosphere. Since the particles in these mysterious emissions have some of the highest energies ever observed in subatomic particles, in some extreme cases exceeding what our particle accelerators can accomplish, it was known that they could affect atoms and molecules they hit, so it seemed possible that they could have other effects as well. Svensmark reasoned that some cosmic ray particles could aid the formation of clouds, by acting as nuclei for the condensation of water vapor. Therefore, clouds would increase during periods of weak solar activity when a reduced solar magnetic field would allow more cosmic rays to reach Earth. The clouds would increase the reflectivity (albedo) of the Earth and cool the climate somewhat. Initially, the theory received little notice when published in the Journal of Atmospheric and Solar-Terrestrial Physics. But in 2006, Svensmark published further work on the theory along with experimental results in Proceedings of The Royal Society A (A is the section of the Society dealing with math and physics) and further confirmation came from a study of weather satellite data by a team headed by Sami Solanki of the Max Planck Institute for Solar System Research in Germany (http://www.mps.mpg.de/en), and a new experiment done at the CERN accelerator by a team lead by James Kirkby (http://cloud.web.cern.ch/cloud/) is expected to offer additional support. Foukal, either unaware of the role of cosmic rays, or choosing to ignore it, missed the most plausible mechanism by which the Sun could alter climate. (continued page 10: Skybox) Photography (continued from page 7) and making a second exposure. Dancer invented a stereocamera that allowed both pictures to be taken at once. He was also reputed to have been a first rate conjurer and juggler! Among the physicists who contributed to photography's evolution, the Scotsman, James Clerk Maxwell (1831-1879) will probably be the name most recognizable to Asterism readers. While almost all photography done in that era was black and white, Maxwell demonstrated before the Royal Institution in London in May of 1861 how a color image could be made. Three images, each through primary color filters, were taken and then projected using three corresponding filters so they overlapped and aligned to make a full color picture. While the process was too cumbersome to be practical at first (and hand-tinting of slides were still used), this RGB (red, green, blue) model for color formed the foundations for modern color film - and even color rendering on your computer monitor! Though digital imaging is fast replacing traditional photography, we still refer to our digital camera when we take snap-shots - terms that pay homage to the role astronomers played in its history. Skybox (continued from page 9) GOOD AND BAD INFLUENCE The moral of this story is that, despite the cultural dogma and what people would like to think, the Earth does not exist in isolation from its solar system neighbors. Tons of meteoritic material and dust fall every year, auroras and other such phenomena affect much of our modern technology (from cell phones to GPS navigation), and Sun's light provides the energy for most life on this planet. Now we can add its protective magnetic field, and the cosmic rays it shields us against, as another way the Sun and its activity affect things here on Earth. Letter from Dr. Lew Thomas Dr. Dale Gary had a superb article last month about our asteroid, Amastrinc. The calculations were great and the logic tight. May this amateur take one small step further: Gary calculates the radius of the asteroid as 5.93 km or 5,930 m assuming it is spherical and composed of rock. Now, the density of rock on the Earth ranges from about 2.5 to 3.5 gm/cc. Let's call it 3 gm/cc. So the rock density becomes D = 3 x 1003 / 1000 = 3 x 103 kg/m3 Assuming a spherical asteroid, as did Gary, its volume is V = 4/3 pR3 = 4.19 R3 = 8.72x1011 m3 The mass of this asteroid using the assumed density is Mass = DV = 3 x 103 8.72x1011 = 2.6 x 1015 kg Gravity constant is G = 6.672 x 10 -11 m3 / (kg s2) The surface acceleration of gravity must then be g = GM/R2 = 6.672 x 10-11 x 1.47 x 1015 /59302 g = 0.0050 m/s2 For comparison, the value of g on earth is gE =9.8 m/s2 and the ratio is 0.0050/9.8 = 0.00051 A 300 pound man would weigh 0.153 pound on Amastrinc! (since Weight = mg) I will leave it for others to calculate this asteroid's escape velocity and to determine if one could leave the surface forever by just jumping. Stunning Beauties (continued from page 3) The rover images are well organized by Sol (day) and type of camera used (Pancam, Navcam, Hazcam, Microscope). And the website is updated on a daily basis. All of the officially released Panoramic and 3-D images have also been organized from the landing day to the present for convenient viewing. A breathtaking collection of Martian landscapes (including this sunset) is beautifully reproduced in the new book titled "Postcards from Mars" by rover imaging team leader Professor Jim Bell (Cornell). Please contact me if interested in purchasing an "autographed" copy or for further information about the Mars Rover missions. All images taken by both rovers are freely available to the public at the JPL Mars Rover website: http://marsrovers.jpl.nasa.gov Here are links to the sunset image and a special effects enhanced image with the rover inlaid approximately to size: http://photojournal.jpl.nasa.gov/jpegMod/PIA07997_modest.jpg http://marsrovers.jpl.nasa.gov/gallery/specialEffects/spirit/images/ PIA07997_plusRover-A667R1_br2.jpg Dr. Ken Kremer NASA JPL Solar System Ambassador Email: kremerken@yahoo.com 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 Membership Chair or Treasurer, or by mail to: AAI P.O. Box 111, Garwood, NJ 07027-0111 DR. LEW'S SEMINARS Some of the topics for upcoming seminars include: " Rotation of the Milky Way " Size of the universe " Measurement of the speed of light (modern and ancient methods) " Review of Celestial Coordinates (choice of topic depends on the interests of those in attendance) FRIDAYS AT SPERRY January 26, 2007 Astronomy on the Thames: Slouching Towards Greenwich Kathleen Quinn Vaccari February 2, 2007 Now That You Bought A Telescope, What Will You Do With It? Steve Clark February 9, 2007 The Geometry of Orbits Al Guzman February 23, 2007 Optics: Lenses, Prisms, and Polarization Dr. Lew Thomas All schedules above were accurate at time of publication. Please check www.asterism.org for latest information (click on "Club Activities") SPECIAL THANKS Ink-saving Logo for Asterism credit: Justin Shapp DOME DUTY SCHEDULE Feb. 2 Team E Feb. 9 Team A Feb. 16 Team B Feb. 23 Team C MEMBERSHIP DUES 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 Theater In The Sky by Ron Ruemmler February 2007 presents Saturn at opposition from the Sun, rising at sunset and visible all night. For the last ten years, the Ringed Planet has brightened to negative magnitude at opposition, reaching - 0.5 in 2002. No longer. Listed as magnitude 0.0 this month, Saturn will remain dimmer than that for the next two decades. Not only is the planet moving into the part of its orbit most distant from the Sun, but the glorious rings are rapidly flattening out as viewed from the Earth. Still, Saturn is brighter than any visible star except Sirius, with which it shares the southeastern sky. At magnitude -1.4, the Dog Star is over 3.5 times as bright as Saturn. After Saturn has risen above the eastern horizon, look for Regulus, the heart of Leo the Lion, below it and slightly to the left. Because the Earth moves faster than Saturn, the planet is now retrograding away from Regulus. In April Saturn will resume direct motion toward the star. Unfortunately, their close conjunction in September will occur just after both objects pass behind the Sun. Two negative magnitude objects are low in the west-southwest about an hour after sunset during the first week of the month. Venus is around magnitude -3.9 all month, while Mercury starts the month at a still impressive magnitude -0.9 about five degrees to the lower right of Venus. But, by the middle of the third week, Mercury is lost in the glare of the Sun, while Venus continues to move out of evening twilight. The last two planets require a cold early morning wakeup. Jupiter is an easy object high in the southeast, while Mars continues to be a challenge rising just at the start of twilight. As usual, the Moon provides a fine guide to the planets. The Full Moon is glaringly close to Saturn on Groundhog Day, while a very low waning crescent Moon passes below Jupiter on the 12th. Finally, a beautifully thin waxing crescent Moon is directly above Venus on the 19th. A comment I made last month about our unusually close perihelion distance (91,399,744 miles) this year elicited a question from an interested member. I stated that the small distance between the Earth and the Sun at that time might be related to the occurrence of the Full Moon a few hours earlier. How could there be a connection? My thinking was that, since the Earth and Moon revolve around their common center of mass, the position of the Full Moon at its maximum distance from the Sun might result in the Earth attaining an exceptionally small minimum distance. I hope that makes sense. FEBRUARY SKY CALENDAR 2 Fri 12:45 AM Full Moon 2 Fri 8:00 PM Moon lower left of Saturn; occultation visible from Finland 7 Wed 1:00 PM Mercury at greatest elongation from the Sun 7 Wed 6:45 PM Uranus one degree upper right of Venus 8 Thu 11:00 AM Neptune passes beyond the Sun into the morning sky 10 Sat 4:51 AM Last Quarter Moon 10 Sat 1:00 PM Saturn at opposition from the Sun 11 Sun 12:00 PM Equation of time at annual minimum; sundials 14.26 minutes slow 17 Sat 11:14 AM New Moon 23 Fri 12:00 AM Mercury passes between the Earth and the Sun into the morning sky 24 Sat 2:56 AM First Quarter Moon Stunning Beauties of Our Solar System By Ken Kremer Pictorial Supplement We are living in the golden age of space exploration. Foreign and domestic space agencies make available to all of us a steady stream of beautiful images which are not only rich in visual detail, but often also illustrate a bit of previously undiscovered science. In my role as a NASA Solar System Ambassador, I am excited by each day's beauties as they arrive in my inbox. Here for your enjoyment are a small sampling of the images that caught my attention this month. A Faint Ring Shines (continued next page: Pictorial Supplement) Pictorial Supplement (continued from previous page) by Ken Kremer Splendor from the North Pole of Saturn Pictorial Supplement (continued from previous page) by Ken Kremer First Light from STEREO: Solar Terrestrial Relations Observatories The twin STEREO spacecraft are NASA's newest Solar Observatories and their mission is to provide the first 3-D view of the Sun, solar activity, and coronal mass ejections (CMEs) - immense magnetized clouds of material which explode off the Sun, towards the Earth and into the solar system. Following the launch, lunar gravitational swing-bys on 15 Dec 2006 were used to redirect both observatories into new orbits. The two STEREO spacecraft are now orbiting the Sun, one speeding "Ahead" of Earth, dubbed STEREO A and the other lagging "Behind" the Earth dubbed STEREO B. They will provide two points of view with which to provide a global picture of the Sun and to study the origin and evolution of solar flares and CMEs and assess the potential threat to Earth. http://www.nasa.gov/mission_pages/stereo/news/first_light.html Full details about the STEREO mission and results are available at the mission website and image gallery: http://www.nasa.gov/stereo http://stereo.gsfc.nasa.gov/gallery/gallery.shtml Links are also provided from the AAI website. Click Other Links > Space Missions Please contact me for further information or public outreach presentations. Dr. Ken Kremer NASA JPL Solar System Ambassador Email: kremerken@yahoo.com Clearing (Continued from page x) by Jeremy P. Carlo Let's define a parameter (Greek letter mu), which is defined as the mass of the putative planet divided by the total mass of all other objects within its orbital annulus: A large would correspond to a "true" planet, traveling in a relatively clear orbit, with nothing substantial in size relative to the planet in the orbital path. A small , on the other hand, indicates that the putative planet is surrounded by a substantially larger amount of debris and is thus not worthy of planethood status. is called the "planetary discriminant" and was proposed by Alan Stern and Steven Soter. Below is a table (adapted from Ref. 1) estimating the values of in descending order for the nine planets plus a number of proposed planetary objects: Earth makes a strong showing, with the highest of all the planets, while Mars and Neptune take a performance hit from roving asteroids and KBOs. But note that the eight planets from Mercury through Neptune all have values of that are in the range of 5,000 to over a million. On the other hand, the five additional objects I included (the two largest asteroids, Ceres and Pallas, the two largest trans-neptunian objects Pluto and Eris, plus Pluto's moon Charon) all have values of < 1. If you were forced to draw a cutoff line, you'd draw it between Mars and Ceres, between which a drop in by a factor of nearly 100,000 is observed. (Just beyond the bottom of the table are a host of objects with 0.01 and less, consisting of the large asteroids and trans- neptunian objects, so there's no second sharp cutoff.) Thus Mercury through Neptune have relatively "clear" orbits, while the latter objects do not. Mercury through Neptune thus qualify as planets, whereas the remaining objects do not. I should note that an accurate determination of depends on knowing how much "stuff" is contained within the orbital annulus, which is quite uncertain in the case of Eris, and not determined accurately in the cases of Pluto and Charon. However, the uncertainties are far smaller than the four orders of magnitude required to bump either Pluto or Eris into the "planet" category, so aside from some jostling among the bottom ranks, no change is going to occur. Now, one could argue that the IAU definition states that a planet must have cleared its neighborhood. However, just because an object orbits in a "clear" annulus doesn't mean it was responsible for that clearing. Is there another parameter that measures how effectively a planet is (theoretically) able to clear its orbit? A parameter (lambda) was proposed by Alan Stern and Harold Levison, and is defined as = M2 / P Here M is the proposed planet's mass (in units of the Earth's mass), and P its orbital period (in years). (Continued next page) represents how effectively a planet is able to clear its neighborhood of debris through gravitational interactions. The more massive the planet, the stronger its gravitational influence and the more effective it is in sweeping out its area. It turns out that this effectiveness is proportional to M2. And the larger the orbit (or equivalently, the less frequently the planet visits a given sector of its orbit), the longer it takes to clear the area, so P appears in the denominator. has an empirical advantage over in that it only requires knowledge of an object's orbital period (accurately known in all cases) and its mass (known to high precision in all the above cases except Ceres, Vesta, and Eris, whose masses are still well-constrained). Once again we can construct a table (adapted from Ref. 1) in descending order of values of (set up so that Earth = 1): This gives a more expected result, with massive Jupiter holding its place as "king of the planets," and, after that, a roughly descending mass-ordered list (Venus and Uranus finish ahead of the slightly more massive Earth and Neptune, respectively, because of the latter's larger orbits to clear). And again there is a clear jump (five orders of magnitude) between the same eight "planets" and the five additional non-planets included. Neither parameter lends any support for Pluto planethood. In fact Pluto isn't even the first runner-up! According to , Eris is the leading candidate among the non-planets, while lends that title to lowly Ceres. But in either case there is a 4-5 order-of-magnitude gap that needs to be breached by any planetary contender, and current observational uncertainties permit nowhere near that large a jump. Clearly, there are eight objects which belong in the "planet" category according to both discriminants discussed. And there are additional objects, foremost among them the five objects listed in the tables above, which belong to one or more separate categories. Perhaps it makes more sense, as Clif Ashcraft suggested, to have multiple non-planet categories for rocky and icy dwarfs, for example, but what is clear is that Pluto and the other proposed planetary contenders do not meet the same criteria as the "classical" planets. 1. Steven Soter. What is a planet? Astronomical Journal 132, 2513-2519, 2006. Available at http://tinyurl.com/wgfto