Solar System model harbors outdated information

Every semester, professors update their textbooks of choice to ensure they are following curriculum that is up-to-date. With that in mind, shouldn’t the campus of Sam Houston State University also reflect the same level of modernism?

Along the walkway between the Estill building and Austin Hall lie 11 stainless steel plates which represent the sun, nine “planets”—including Pluto, and the asteroid belt. Reduced by 30 billion times, the astronomical objects and the distance in between them are proportional to how they are in outer space.

The display, though precise in scale, is not necessarily as accurate in the information it contains. However, in 2006, 424 scientists came together at the International Astronomical Union in Prague of the Czech Republic to redefine what it means for an object to be considered a “planet.” This change stripped Pluto of its planet status.

According to Gwen Penny, assistant to the chair of the physics department, the plaques were dedicated by former chair Russell Palma, Ph.D. and associate professor of physics Frank Cooper in the early 1990s. Although at the time of the tiles’ initial unveiling, Pluto was still considered a planet, eight years after the pivotal decision was made, Pluto’s description remains on the plate as “the smallest planet in the solar system.”

“If there are any updates, it would be better to add the other dwarf planets than to remove anything,” Pooley said. “Ideally, the plaques should reflect our current classification scheme. Pluto is still out there doing its thing, so it’s not ‘wrong’ to have a plaque for it. But by that reasoning, it makes sense to have plaques for Ceres and Eris and the other dwarf planets.”

“It was clear that the definition needed revision since at the time there were over 1,200 objects that fit the then current definition of ‘planet’,” assistant professor of physics David Pooley said. “It’s worth noting the definition of ‘planet’ has changed many times.  It originally meant a star that wandered around, occasionally moving in a direction opposite to all the other stars in the sky.  It was later changed to only mean only things that orbited the sun.  However, by this definition, there were 65 known ‘planets’ in 1859.  So the definition was changed in 1860 to exclude minor objects (in the asteroid belt).   What happened in 2006 was just another iteration of this process.”

As of eight years ago, the current definition of a planet is a celestial body which is in orbit around the sun, has sufficient mass to assume hydrostatic equilibrium—a nearly round shape—and has “cleared the neighborhood around its orbit.” The first two criteria are what constitute a “dwarf planet” and the last criteria helps to refine what a “planet” is.

Although the decision came as a surprise to many people and stirred up a lot of controversy, according to Pooley, it is not a matter of fact or opinion.

“It’s neither.  It’s just taxonomy,” Pooley said. “It’s an attempt to group things into meaningful categories so that a deeper understanding can be had. Classification is the first step in making sense of things and it’s important to get it as correct as possible; however, it is certainly subject to change.  One of the strengths of science is its ability to adapt to new information that comes to light. In this case, there was a growing body of evidence, based on new discoveries, suggesting that we needed to refine how we classify certain objects in our Solar System.”

Although the redefining of the word “planet” brought about much discourse in the public, according to Pooley it wasn’t nearly as influential in the world of astronomers.

“[The decision affected us] very, very, very, very little,” he said. “This was a minor event for almost every single professional astronomer I know. It was huge in the public sphere because it changed grade-school curriculum that everyone was familiar with, which may have given the impression that it was a big deal scientifically, but it really wasn’t.”

Although to this day, many people still argue about whether or not they consider Pluto a planet, Pooley said he doubts there will be any future decisions counteracting the decision in 2006.

“This issue has been settled in the minds of most astronomers,” he said. “Besides, while definitions and classifications are important, they are one of the least insightful aspects of science. The object we call Pluto is still there and still has the same physical characteristics it did before the reclassification.  Whether it’s called a ‘planet’ or a ‘dwarf planet’ is a rather boring scientific question. Professional astronomers have much more interesting questions to investigate.”

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