Star Points for July 2011 by Curtis Roelle One Neptunian Year Later This month Neptune completes its first circuit of the Sun following its discovery in the year 1846. With a distance from the Sun 30 times farther than the Earth's, the eighth planet requires 165 earth years to perform one orbit around the Sun. The discovery of Neptune is one of the best mystery stories in all of astronomy. It involved careful observations by alert observers, mathematical puzzle solving, and international competition and cooperation. Neptune's discovery wasn't an accident. It was the prize in a 19th century space race. For millennia, our human ancestors around the globe were aware of five "wandering stars" in the sky — Mercury, Venus, Mars, Jupiter, and Saturn. They were also aware of the Earth, even though they may not have understood its planetary nature. No single person was ever credited with discovering any of these six planets. That all changed in 1781 when William Herschel discovered the planet Uranus while observing with a telescope from the garden of his house in Bath, England. With his discovery Herschel became the first person in recorded history to discover a planet of any kind — major or minor — orbiting the Sun. Forty years after its discovery, new observations of Uranus indicated that the planet was slowing down. Was there a flaw in Sir Isaac Newton's laws of physics, or was Uranus being tugged on by the gravitational pull from some other unknown planet? The director of the Paris Observatory in France assigned the mathematical astronomer Joseph Le Verrier the job of solving the mystery. Simultaneously in England, the young astronomer John Couch Adams took up the same issue, in his spare time. These efforts involved endless hours of performing painstaking calculations, without the aid of electronic computers, to pinpoint the position of an unknown and unseen world. The part-time nature of Adams' effort seems to have resulted in lower urgency for following up his predictions with confirmatory observations. When observations were attempted, they suffered from a lack of suitably detailed star charts. On the other hand, Le Verrier published his predictions in a prestigious journal. Using a new and very detailed Berlin Academy star map, German astronomer Louis d'Arrest was able to immediately locate and identify the new planet per Le Verrier's prediction. The Frenchman received due credit for discovering the planet using his pen. Subsequently, the English attempted to save face by pointing out that Adams had likewise managed to calculate Neptune's location mathematically, and in the year prior to Le Verrier's published results. That served to enrage both the English, who were deeply embarrassed by the perception of bumbling a missed opportunity, and the French, who were offended by England's attempt to steal credit from France for its own coveted scientific achievement. The difficulty of the problem cannot be overstated. They had little to work with other than some observations and a few weak assumptions based on flimsy principles. "Had Adams and Le Verrier been working in the 21st century, their predictions never would have found their way into a peer- reviewed journal!" claimed an article in the July issue of Sky & Telescope magazine. This interesting view begs the question, how many discoveries are killed in the nest by the peer review process? The vested interests and ingrained biases of peers, even when wrong, is a difficult hurdle to overcome. Revolutionary discoveries in science are placed at risk through blind adherence to the old saw "extraordinary hypotheses require extraordinary proofs." As the late astronomer and former director of the Celestial Mechanics Branch at the U.S. Naval Observatory Tom Van Flandern wrote in his book subtitled Paradoxes Resolved, "Sometimes (although admittedly not often) the extraordinary hypothesis will be the right one." Neptune is easily within the reach of amateur telescopes. Although I had observed Neptune previously, my first recorded observation, made in 1982 while observing at 50-power, described Neptune's "small but obviously round disc" as being "bluish" in color. The most memorable Neptune observation for me was one evening in 1989, when I first observed its largest moon, Triton. That same night the U.S. spacecraft Voyager 2 was flying past and photographing the moon. Each new image was displayed upon receipt during live television coverage. Due to the distance of Neptune and Triton, their images, traveling at the speed of light, required four hours to reach antennas on Earth. While viewing Neptune and Triton with a telescope, the thought occurred that the images appearing on live television had been taken at the same instant as the view seen in the eyepiece. Their reflected light had also needed four hours, traveling through space, before entering the eye. I was enjoying two live feeds from Neptune at the same time! Currently, Neptune is best observed in the pre-twilight morning sky. If you'd like to try spotting it with your telescope, finder charts are available online at skyandtelescope.com.