StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

AUGUST 2006

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520 AUGUST 6, 2006: Perseids Awash in Moonlight: During the next seven days the moon passes from a thick waxing gibbous shape, through its full phase early on August 9, and finally ends the week on Saturday as a thick waning gibbous moon. Even with a moon drenched sky, there is a silver lining to this story. This is the special week when the greatest number of Perseid meteors fly. Back in the days when men began to look more like women, and women were becoming more liberated—the ’60s (gasp)—I had the opportunity of watching the Perseids under nearly identical conditions. The night was definitely not a washout, but it was awash under a 17-day old moon, the same as it will be this year. I also remember that the sky was unusually clear for the summertime. The six brightest stars of the Pleiades were distinctly visible when they rose above the tree line after 1:00 a.m. My friends and I also had a relatively good location for sky watching on top of South Mountain, just south of Emmaus. Looking over my records for that evening, meteor rates were between 10-15 events per hour until after 3 a.m. Between three and four a.m. we saw 16 Perseids, but the next hour netted us 34 meteors, all Perseids. The bright moon in the SSE was only 60 degrees away from the radiant. The moon is five degrees closer to the radiant on the best morning which is Sunday. If a Perseid party is in your mix, observe after 3 a.m. Face away from the moon. You’ll see nothing if the brilliant moon is in your field of view. Hot caffeinated beverages are always good items to have on hand. Make sure that you are comfortably warm, and cover your sleeping bag or bedding with a plastic tarp to keep it from becoming wet from dew. A map is posted at the URL below. Click on the StarWatch button. Party hardy!

521 AUGUST 13, 2006: T-Rex Not Included!: I just completed my second four-week astronomy volunteering stint at Bryce Canyon in SW Utah. It rained a lot. I was offered money—$10.00—to leave the Park early. Rosalee in concessions said she’d watch on the weather loops “those dark clouds move eastward” as I journeyed home. So when the skies cleared on my last evening at Bryce, my wife and I decided to take moonlit photos from the canyon floor. A fat Luna climbed above the red burnished limestone cliffs right on cue. Jupiter appeared in a steel-blue sky as ephemeral shadows began to follow our ascent along the Queen’s Garden Trail. It was finally dark enough for a picture, so I setup—tripod, camera, lens hood, and cable release. Click! My first 60 second exposure began! The light dimmed as a cloud literally condensed in front of the moon. I could not believe my luck. Irate, I disassembled my gear, folded the cable release and shoved it into my jeans pocket for easy access. We hiked back to the rim without headlamps, amidst the diffusely lit hoodoos and spires which make Bryce so famous. The moon reappeared, flooding the landscape with a crisp, new silvery light. “One last shot,” I mused. I assembled my gear, but there was no cable release in any of my pockets. Somewhere along the switchbacks it lay, waiting for some happy Japanese tourist to find it in the morning. No Way! Back down I went, battling the mental images of rabid chipmunks, prairie dogs, and the occasional stalking cougar. Lightning began flashing in the distance. My heart raced. I found it in less than 10 minutes and returned to the rim on an endorphin runner’s high. Reassembling, I imaged a gothic, moonlit landscape punctuated by explosive bolts of distant lightning. Where was my T-Rex? Photos online…

522a AUGUST 20, 2006: Name the 12 Planets!: Name the twelve planets that orbit our sun in their correct order. They are Mercury, Venus, Earth, Mars, Ceres (former asteroid), Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, and 2003UB313. The world clearinghouse for astronomical data, the International Astronomical Union, has finally provided an authoritative definition for a planet. "A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet." In the case of the Earth, the matter from which our planet is composed produces a sufficient amount of gravity to overwhelm the structural integrity of this material. This causes the Earth’s mass to collapse into the shape of a near sphere. “A pair of objects, which each independently satisfies the definition of ‘planet,’ is considered a ‘double planet’ if they orbit each other around a common point in space that is… not located within the interior of either body.” A majorette twirls a baton at the balance point between both ends, which in astronomy, is called the barycenter. Since Pluto and its companion, Charon, are both spherical, but the barycenter of the system lies outside the boundaries of each body, Charon, Pluto’s former moon, and Pluto now become the solar system’s first double planet. If the barycenter lies within one of the two bodies, and the more massive object fits the definition of a planet as noted above, then the secondary object becomes a satellite. The first dozen planets are only the beginning of a much larger playing field. Currently, there are another 12 candidate planets under scrutiny.

522b AUGUST 25, 2006: Planet Police, Stand Down: Astronomers have just given Pluto the official boot and reorganized the Solar System into an arrangement of eight classical planets, dwarf planets, and smaller bodies. Gone are the 12 planets that were proposed by the IAU earlier in the week including Pluto which has been in limbo for the last decade. Gone from planetary status are also Ceres; Pluto’s moon, Charon; and 2003UB313. What has occurred is a tightening of the definition of a planet without sacrificing any science. A planet is now “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” Part “c” is an ingenious addition to the explanation because it declares that in order for an object to attain planetary status, it must possess a sufficient amount of gravity to have pulled into itself the debris that lies in its path. That is precisely why Pluto and the hundreds of other Kuiper Belt objects never coalesced into planets. They had too little mass and were too far apart from each other. The IAU then went on to define a new classification of solar system objects called dwarf planets. “A dwarf planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.” Finally, all of the other objects orbiting the Sun “shall be referred to collectively as Small Solar System Bodies.” These include all of the meteoroids and comets, and most of the asteroids, and trans-Neptunian bodies. Planet police, stand down.

523 AUGUST 27, 2006: Don't Buy a Star, Catch a Fallen One: Readers of this column may have heard about the International Star Registry, a company which purports to be able to name stars for its customers. Prices range from $54-$139, plus shipping and handling, but it is just a gimmick. Only the International Astronomical Union, a worldwide congress of professional astronomers, has the authority to name astronomical bodies. I’d like to suggest an alternative—purchasing a fallen star, a meteorite—a rock from outer space that has struck the Earth. Meteorites come in three basic varieties: Iron-Nickels, Pallasites (stony-irons), and Stones. Respectively, they represent 4%, 1%, and 95% of the witnessed meteorite falls. Iron-Nickel varieties show evidence of flow patterns (thumb print depressions) or have shrapnel like appearances if they exploded near the surface of the Earth. They are by far the most durable and least expensive and what I would suggest for a first time purchase. Pallasites or stony-irons are the most beautiful, but because of their rarity, they can be quite expensive. They show a metal/mineral matrix and are usually sliced and polished in thin sections because their iron/magnesium-rich minerals, mainly olivine and pyroxene, are translucent. Stony meteorites are characterized by a very thin, dark fusion crust from the ablation process as the meteoroid slammed through the atmosphere on its way to striking the Earth. They are the most fragile of the space nomads. Unlike buying a star which requires purchasing a telescope to see it, you can hold a meteorite in your hands and know you’ve got something which orbited the sun virtually unchanged for the last five billion years. Meteorite links and vendors are online with this week’s StarWatch at the URL below.; Tim Heitz: Midwest Meteorites. Tim sells meteorites to support his hobby of collecting fallen stars. His prices are excellent as well as the conversation--www.meteorman.org--636-225-9449.

Bob and Diane Lane, ordervillemine@hotmail.com, Orderville, UT, phone: 435-648-2002 have a small but interesting collection of meteorites including lots of small Sikhote-Alin irons for sale at prices of approximately $25 per item.

Schooler’s Minerals at http://www.schoolersinc.com/ is also a good bet.

Locally, Bey’s Rock Show in Bailey, PA is usually another source of iron-nickel metereorites. Their website is beysrockshop.com,or call: 610-369-0180. Their meteorites have not been overly spectacular.; Meteors, Meteorites, and Impacts
Meteor Crater: The world's best preserved meteorite crater, Winslow, AZ
Meteorite Classification through Photography
Robert Haag Meteorites
Midwest Meteorites: Tim Heitz
The Meteorite Market: Meteorite Exchange
Meteorite Magazine
Meteorite Identification (gone wrong)

August Star Map

August Moon Phase Calendar