August 2007 Volume I, No 2 |
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The Perseids -Sean Tvelia-
Each year millions of amateur and professional astronomers flock to the dark skies for one of the many meteor showers observable in the northern hemisphere. Whether observing for professional purposes or for the opportunity to make thousands of wishes nobody can deny the grandeur and the excitement of a meteor shower. Although the Perseids is not known to produce the greatest number of meteors it is certainly one of the most reliable, typically producing 70 meteors per hour--more than 10 times the average in a given evening. Unlike sporadic meteors (those seen on any evening) Perseid meteors will appear to come from the constellation Perseus -thus giving this shower its name. This phenomenon is due to the earth's position as it travels through space. But what causes a meteor shower? Most, if not all, meteor showers are caused by comets. In this case the Persied meteor shower is a result of the comet Swift-Tuttle discovered in 1862. This comet takes appoximately 130 years to orbit the sun and with each pass it leaves bits of debris in its path. As the earth passes through the debris (facing in the direction of Perseus) small grains, mostly the size of sand, but in some cases as large as marbles, fall through and interact with our atmosphere. Friction from this interaction causes the debris to heat up and excite the surrounding atmosphere producing the bright light most people refer to as falling stars. This year the Earth is estimated to pass through the thickest area of debris in the early morning hours of August 12 which could produce up to 70 meteors per hour. In the darkest areas, such as those at Montauk Observatory, this will make for a fantastic display, and we hope all will join us at the observatory for a great night of observing and star gazing beginning at 9. If you wish to bring your own telescope please be on site by 8:30 to begin setting up. |
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Other Solar Systems - Sean R. McCorkle- For those of us raised on a steady diet of science fiction and the likes of Star Trek, the concept that the galaxy is filled with solar systems is usually taken for granted---that there are planets orbiting other stars goes without saying. This notion goes back to the late 1500's, when Giordano Bruno wrote that the stars we see at night were innumerable and were actually distant suns which were orbited by planets like our own; we just didn't see any planets because they were so far away. It's one thing to believe in this conjecture. Much more exciting is that, in the last decade or two, it has been confirmed. There really are other solar systems, and there appear to be a lot of them. Currently there is evidence for over two hundred planets orbiting other stars. In most of these cases, the planets have not been seen directly. Interstellar distances are vast, even when compared to the sizes of solar systems. Any planets would appear very close to to their stars, where their faint light gets drowned out by the much brighter light of the star, which is a challenge that even the Hubble Space Telescope can't seem to surmount. Instead, we largely rely on Newton's laws to detect these solar systems. We may be accustomed to thinking that the planets in our solar system orbit the Sun, which is relatively fixed. But as a planet orbits a star, it induces a small motion in that star. That's because the force of gravity is a two-way street; two bodies floating in space exert a gravitational pull on each other, and each moves according to that pull. Like two dancers or ice skaters swinging each other around, if their masses are equal, they will orbit a "center of gravity" halfway between each other. If one body is more massive than the other, the center of gravity will be closer to it. But the bigger body will still move in an orbit, although smaller. No matter how extreme the difference in masses, even if one body is a star and the other is a planet, the bigger body will still move in an orbit, although it may be imperceptibly small. It is very difficult if not impossible to actually see these small planet-induced motions of stars because they lie at such great distances from us. However, in recent years for some stars, it has become possible to detect these oscillations in their velocity, by monitoring the Doppler shift in their spectra. The Doppler effect, the same effect that causes train horns or vehicle sirens to seem to change pitch as they zoom past you, also causes light to change wavelength in the same manner: the frequency or wavelength of the moving object appears to shift in proportion to its velocity in In order for an extra-solar planet (or exoplanet) to be detected by this method, two conditions must be met. First, the motion has to be largely directed towards us or away from us (along the line of sight) in order to create a Doppler shift. This limits us to solar systems which we view edge on. Second, the magnitude of the shift must above the threshold which we can measure. The faster the star moves in its orbit, the easier it is to see, which means that if the planet has high mass or orbits close to the star (gravitational pull is stronger), we have an easier time detecting it. Fortunately, there are so many, many stars, that the fraction of those which meet these criteria is still a large number. The first confirmed case of a planet orbiting a star like our Sun was 51 Pegasi (in the constellation Pegasus, this star star is visible to the naked eye on a good, dark night). The velocity and knowledge of the star's mass allows us to infer the exoplanet's mass and orbit size; the planet is roughly half the mass of Jupiter, but its orbit size is 7 or 8 times smaller than that of Mercury! Most of the exoplanets discovered by this method have been large, between 1 and 10 times the mass of Jupiter, with orbit sizes between that of the Earth and Jupiter. But this is not to say they are the most common -- it's just that these are the easiest for us to find. Many many more small planets may lie below detection limits. The push is on to extend sensitivity to find smaller and smaller planets. Other detection methods are being developed. Several stars are now known to have multiple planets. In 2005 an international group obtained an infrared image of an exoplanet near its star. This particular star is a relatively faint brown dwarf, and the planet is 5 Jupiter masses, in an orbit one and half times the size of Pluto's orbit. The same team reported signs of water molecules in the spectrum of the planet. Last month saw a report of water in the spectrum of a so-called "hot jupiter" (large mass, close-in orbit). One burning question remains: how many planets are earthlike and are in "comfort zone" or earthlike orbits? Stay tuned .... For additional information, lists of known extrasolar planets and their properties, see http://exoplanets.org/. |
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Observer's Report -Tom Madigan- As a member of the Montauk Observatory Advisory Board, I am pleased to report that there has been much activity at the observatory. After an observing session at the County Park in Montauk, Friday night, June 22nd, I was ready to sell my home in Patchogue and move out there! There is simply no way to describe the breathtaking Milky Way and the rest of the night sky as witnessed that night. It was one of the best views of the night sky I have ever seen in my 45 years of Astronomy and one I won't soon forget. With the new telescope, the Trifid Nebula (a beautiful gas cloud located in the direction of the Milky Way's galactic center) looked like it does in pictures, only better! M82, a fascinating galaxy located in Ursa Major (a constellation that contains the Big Dipper) was big, bright and detailed! We easily saw the central star in the Ring Nebula, a famous object high overhead this time of year, located in the constellation of Lyra. It is the remnant of a star that has undergone its end-of-life processes, ejected its outer layers and now glows because of the super-hot white dwarf star that remains at its center. Through even a modest telescope, the nebula looks like a cosmic smoke ring. M4, a Globular Star Cluster just to the west of Antares in Scorpius, was spectacular and resolved to the core; M13, another famous Globular Star Cluster in the constellation of Hercules, was indescribably beautiful. Even with the 1/4 moon, the Milky Way was stunning. After moon-set at about 11:30 PM, the background became jet black with the stars beacon-like and the Milky Way bordering on casting a shadow. The only way to describe it is "Brilliant"!
5 July 20 July Dr Mike Inglis presented another fabulous lecture titled "Mars, Water, and the Search for Life" to a great crowd at the Montauk Public Library. In his lecture Dr. Inglis showed participants some of the newest images taken by Mars rovers and orbiters and described the geologic significance of the data and how some of the data shows evidence of recent flowing water on Mar's surface. 3 August
Professor Sean Tvelia of Suffolk County Community College, and member of the Executive Board of Montauk Observatory, presented a lecture on Lunar Folklore at the Montauk Public Library. The lecture was well attended and followed by an observing session at Theodore Roosevelt County Park with the Long Island Beach Buggy Association and lecture attendees. |
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OBSERVING NIGHTS, LECTURES & PLANETARIUM SHOWS Montauk Observatory For more information regarding Montauk Observatory events contact seant@montaukobservatory.com Custer Institute For more information regarding Custer Institute events contact CusterDonna@yahoo.com
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Observing Highlights for August-September Naked-Eye Planets for August- September 2007
Key Dates August-September: |
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August
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September
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Contributions Welcome Montauk Observatory is always looking for people who would like to become more involved with the observatory. One of the easiest ways to become involved is to contibute an article or an essay to The Observer. If you would like to make a contribution to this newsletter please send your article or essay to montaukobserver@montaukobservatory.com.
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David Larkin, President |
Dava Sobel, Author |
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©2007
Montauk Observatory