ISU Bengal

Issue date: 1/31/07 Section: Life

Media Credit: Alisha Clark Dr. Steven Shropshire delivers his presentation on the controversy of Pluto.

The debate over whether Pluto is a planet or not has been raging for 6 years now, and as you may know, recently came to a conclusion that made many people very unhappy. On Aug. 24, 2006 the International Astronomical Union (IAU) defined the term "planet" for the very first time, and this excluded Pluto, putting it into a new category of "dwarf planet". Last week, a workshop hosted by Dr. Steve Shropshire discussed the facts and myths surrounding the controversy.

Steve, a self-described layman of astronomy, addressed the redefinition as a "consensus" among scientists. At the workshop, he said "Science isn't something that can be accomplished by one man alone. In fact, no theories ever come into existence from an individual or even a few individuals, because everything put out by scientists is unfailingly scrutinized and dog-piled until only the most logical and accurate theories survive. By the time a hypothesis becomes a theory it has been tested and retested by hundreds or thousands of scientists".

The definition that the IAU came up with has three conditions. First, it needs to orbit the sun. Second, it needs to have sufficient mass to be nearly round. And last, it needs to have "cleared the neighborhood" around its orbit. Any satellite fulfilling only the first two conditions is a dwarf planet. It is important to note that though a dwarf star is still a star and a dwarf galaxy is still a galaxy, a dwarf planet is not a planet. This is exactly what happened to our oh-so-recently ninth planet Pluto.

Historically, it was never necessary to define planets. It was once believed that Pluto was larger than Mercury. By 1978, however, with the discovery of Pluto's moon Charon, things had changed drastically. By using Charon's orbit, they were able to accurately determine Pluto's mass for the first time and found that it was not only smaller than Mercury, but a fraction the size of Earth's moon, making it easily the smallest planet in the system. After some time, scientists began to become irked at Pluto's differences. It was far too small and had an unusual orbit.

Finally, the IAU came up with a definition. In the first stages, the definition would've kept Pluto and added 3 new planets, bringing the total to 12. Charon, Eris, and Ceres would've been added to our solar system as fully recognized planets. Interestingly, Ceres is an asteroid that became so large it gained enough gravity to compact into a nearly round shape, thus qualifying it for planet status. However, when the voting was finished, the condition was added that a planet must have "cleared the neighborhood around its orbit". What exactly this was supposed to mean was not clearly understood even by the scientists. Having come to this intentionally vague concept agreeably, they went ahead and changed the history books, then called it a day.

Continued...

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