StarWatch for the greater Lehigh Valley

MARCH  2003


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

[Moon Phases]


340    MARCH 2, 2003:   Water on the Moon
NASA's and the Dept. of Defense's Clementine satellite started the controversy about the moon having water with its late November 1996 discovery of ice in a six-mile deep crater near the lunar south pole. Smaller craters on the 6-mile deep Aitken Basin never receive sunlight. The temperature of these shadowed regions has been measured at a permanent -387 degrees Fahrenheit, sufficiently cold to allow frozen water to remain exposed to the lunar vacuum for billions of years. Keep in mind that only one orbital pass of Clementine gave a radar signature of water. In 1998 another robotic satellite, Lunar Prospector, rekindled the debate with its data suggesting that frozen water was contained on crater floors of both the lunar north and south poles. Prospector indicated that the water was mixed in low quantities of one percent or less with the lunar regolith (soil), but that pockets of nearly pure water totaling an area of 1300 square miles, with a volume of about 1.4 trillion gallons existed just beneath the lunar surface. However, the controlled crash of the 316-pound (158 kg) Lunar Prospector spacecraft into a permanently shadowed crater near the south pole of the moon on July 31, 1999 produced no observable signature of released water vapor according to observations made from earth and with the Hubble Space Telescope. More importantly, the 838.2 pounds of lunar samples returned to earth by the Apollo astronauts showed that the moon never had any water locked within its rocks, something that every terrestrial stone possesses. If the moon does contain water from past cometary hits, it will drastically lessen the cost of transporting water to the moon, now estimated at $2,000 per quart, when the exploration of the moon resumes in the 21st century.

341    MARCH 9, 2003:   The Beehive
During the next two months take the opportunity to observe Jupiter with binoculars high in the south between 8 p.m. and 10 p.m. It will be a great way to become familiar with a famous open cluster of stars called the Beehive or Praesepe. Jupiter and the Beehive will easily fit into the same binocular field of view. The Beehive or M44 was the 44th object cataloged by the famous French comet hunter, Charles Messier (1730-1817), who used small refractors to sweep the heavens in search of these icy interlopers. He was the first person in France to view Halley's Comet on its first predicted return in 1758, and this got him hooked on discovering more. Messier went on to bag 21 comets, but in his diligent sweeps of the heavens, he also came across fuzzy, glowing patches of sky that today we know are star clusters, nebulas, and galaxies, but to him could have been mistaken for comets. Not wanting the embarrassment of announcing as a comet one of one of these fixed objects, Messier made a compilation of these objects in 1781. Ironically, Messier is not remembered for what he was trying to discover, but rather for what he was trying to avoid. The 110 Messier objects in the standard catalog represent some of the finest celestial gems of the northern sky. Through binoculars or a small telescope at low magnification, the stars of the Beehive resemble a swarm of hovering bees. The 200 stars are located some 600 light years away in the constellation of Cancer, the Crab. These luminaries were born about a half billion years ago, but the stars have not yet managed to escape the birthing nest that is about 15 light years across. Jupiter is near the Beehive through late April, so there will be plenty of time to view this sparkling gem of early spring.

342    MARCH 16, 2003:   Happy Springtime!
I cannot believe that this Friday at 8:03 p.m. marks the start of spring. As much as I enjoy the unexpected snows of winter, watching the sun from my kitchen window finally rise behind the big pine tree about a half block away is my natural signal that spring has arrived. If we are to get a snowy day henceforth, the precipitation will have to come during the cooler nights because the increasing height of the sun during the longer days gives us enough energy, even when it's cloudy, to drive the temperature well above the freezing mark. The seasons result from the 23-1/2 degree tilt of the Earth's axis to the perpendicular of its orbital plane and the condition that arises when the axis points in the same direction, which currently is towards the North Star, Polaris. Spring is just that joyous moment when the Earth on its yearly circuit passes the point in its orbit where the northbound sun crosses the celestial equator. The celestial equator is simply the extension of Earth's terrestrial equator projected into space. At the first moment of spring somewhere along the Earth's equator, it is noon and the sun is directly overhead. Henceforth, the Earth's orbital motion carries the sun's overhead, noontime position farther north, until the summer solstice when the sun's zenithal position lies along the Tropic of Cancer. The Tropic of Cancer girdles the globe at 23-1/2 degrees north of the equator. It sounds like an arbitrary position, but it really isn't. It is the same angle that the Earth's equator is tilted to the Earth's orbital plane, caused by the Earth's axial inclination. As our planet revolves, the sun's reflected annual motion in the sky carries it above and below the equator giving mid-latitude locations like the Lehigh Valley a refreshing quarterly change in the seasons. Happy springtime!

343    MARCH 23, 2003:   Change is the Constant
As a kid attending Jefferson Elementary in Allentown and first learning my planet facts, I was once asked to recite the names of our sun's children in their correct order. I chose to start with Pluto and rapidly fired off the names of the planets until coming to Mercury. WOW, suddenly my "lucky star" was ascending. Even the bullies left me alone for a few days, and from that time onward, astronomical facts were often first filtered through me before they were disseminated to the rest of the class. But keeping abreast of new astronomical data in the late 1950s was vastly different from today's rapidly changing scene, even with the help of the Internet. The Planet Quiz Show, which can be found at the URL listed below, has been my attempt to keep Allentown School District pupils in touch with the information explosion. Try some of these facts. Jupiter now possesses 52 satellites, Saturn 30, Uranus 21, and Neptune 11. For a while we thought that Earth had three natural satellites, but we're back to the lonely Moon once again. There probably is no Planet-X although over 700 Pluto-like objects have been discovered beyond the last planet. There has been a longtime movement to declassify Pluto as a planet, but recently some astronomers have begun to say that several of the larger asteroids should be reclassified as planets. The solar system may eventually have eight, nine, or 12 planets. I also can't forget the asteroids, rocky mini-planets, most of them orbiting the sun between Mars and Jupiter. Their numbers are now around 250,000, up from 2-3000 when I was in grade school. Finally, we have discovered beyond our own solar system 105 planets in 91 planetary systems. For today's student, change is the only constant in the new 21st century universe.

344    MARCH 30, 2003:   Kirchhoff's Laws
With the moon new on Monday, this is a good week to go outdoors and view the stars. It is hard to believe that astronomers have been able to obtain accurate distances, luminosities, compositions, motions, and dozens of other properties for all of the stars that we can see with the unaided eye. Our ability to discover these seemingly hidden secrets began in earnest with a German physicist by the name of Gustav Kirchhoff (1824-1887). Kirchhoff, working along with Robert Bunsen (1811-1899), developed the first spectroscope, a device that accurately split light into its component colors. Kirchhoff found that when a solid, liquid, or gas (under pressure) was made to glow, it produced a continuous spectrum, the rainbow of colors with all colors represented. When a rarified gas was made to incandesce, it emitted light at certain specific wavelengths that was always the same for the same gas. But when a gas was placed between an observer and a light source producing a continuous spectrum, an absorption spectrum was created, a rainbow containing thin, dark lines where energy was missing. Kirchhoff realized that the dark lines were at the same positions as the bright emission lines of the fluorescing gases that he was studying. Suddenly, astronomers had the necessary tool for uncovering the composition of the sun, the stars and galaxies, and even the universe itself. The use of spectroscopy has even allowed astronomers to chart the evolution of stars from birth to death. Three weeks ago, my Allen astronomy students spent several days working with Kirchhoff's laws. They helped produce the beautiful image demonstrating emission and continuous spectrums that can be found at Web StarWatch at the URL below.
[Kirchhoff's Laws]
Kirchhoff's Laws Demonstrated:   Allen astronomy student, Monica L. Ward, observes fluorescing krypton gas in a demonstration of Kirchhoff's second law of spectroscopy. The purplish color of the glow tube is the compilation of all of the individual spectral lines that are being created as electrons of the krypton atoms, bumped into higher energy states by rapidly passing electrons, return to lower energy levels. These transitions emit light at very specific wavelengths as the photograph reveals. The light from the flashlight to the left of Monica's head is being created by a glowing tungsten filament and is producing a continuous spectrum according to Kirchhoff's first law. The emission spectrums and Monica were made as a single 15-second digital image by attaching a 30-cent diffraction grating in front of the camera lens and illuminating Monica with a flashlight during the exposure. The continuous spectrum was recorded as a separate image and superimposed into the picture. Photography by Gary A. Becker with the help of Allen students Jarryd Homick, Kristen B. Weaver, Shannon Ruhe, Michael D. Roberts, and Tonya M. Barrett...

March Star Map

March Moon Phase Calendar