Star Points for August 2008 by Curtis Roelle Neptune: Last of the Planets In the wake of the International Astronomical Union's 2006 "recalibration" of major bodies in our solar system, Neptune once again finds itself distinguished by being the farthest outlying planet. That's a distinction it has not enjoyed since the 1930 discovery of what is now referred to as the "dwarf planet" Pluto. Neptune is different from the seven other official planets in various ways. It is the only one that cannot be seen without a telescope. (Uranus is theoretically visible to the unaided eye from a dark sky site.) Neptune is also the only planet whose discovery resulted from the use of mathematics. The associated calculations led to precise predictions of its position in the sky that led to its prompt telescopic discovery. Following William Herschel's 1781 discovery of Uranus, astronomers observed it closely to precisely determine the parameters of its orbit around the sun. By the early Nineteenth Century, however, they realized that Uranus wasn't following its predicted path, and they theorized that gravitational forces were somehow perturbing its orbit. They analyzed the combined gravitational effects of all known planets, but their calculations failed to completely explain the perturbation. Some astronomers postulated the existence of an unknown, eighth planet, and called in the mathematicians. Urbain Jean Joseph Leverrier in France and John Couch Adams in England took up the problem. Adams finished his solution first, but confirmation languished as Adams waited for an observer to corroborate the prediction with a telescope. It seems that the Astronomer Royal was unfamiliar with, and perhaps somewhat skeptical of, the whole idea. In the meantime Leverrier released his results but, likewise, could find no observer in France willing to attempt verification. Eventually, the Berlin Observatory gave it a try and immediately discovered Neptune not far from its predicted position. Early this month, between August 3-7, observers will have a little help in finding Neptune as it passes very close (9 arcminutes) to a star barely visible to the naked eye. To find it you will need a telescope with a good finder scope, plus the ability to read and use a star chart. A good place to find the latter is SkyandTelescope.com. Navigate to "Celestial Objects", then "Planets", and "How to find Uranus and Neptune". On that page are links for advice on observing and a chart depicting Neptune's place in the sky, including the 5th magnitude star Neptune passes just south of. The best time to view Neptune in early August is an hour or two after midnight, when it is highest in the sky. In small telescopes Neptune usually looks like a blue star. In larger scopes, it often looks like a beautiful, very small, blue disc. If you don't have a telescope, the Westminster Astronomical Society ("WASI") will provide free telescopic observing on Friday, August 8, following a planetarium show at Bear Branch Nature Center. The star party will begin, weather permitting, when the sky darkens sufficiently. The nature center collects a nominal fee ($2) for the planetarium program and recommends that guests register by calling the Parks Department at 410-386-2103 (M-F, 8 a.m.-5 p.m.).