Pluto Is A Planet Again: Florida Astronomers Discover The Hidden Reason Behind A Fatal Flaw In The Old Definition

Monday, 10 September 2018 - 11:57AM
Science News
Monday, 10 September 2018 - 11:57AM
Pluto Is A Planet Again: Florida Astronomers Discover The Hidden Reason Behind A Fatal Flaw In The Old Definition
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For some, Pluto always has been and always will be the ninth planet in our solar system. Back in 2006, the International Astronomical Union rendered every science textbook useless by altering the definition of what constitutes a planet and demoting Pluto's status to dwarf planet. According to Science Daily, a new study argues that Pluto's demotion was invalid, and that it's high time we got our "numero nueve" back.

The reason the updated definition of a planet was a blow to Pluto is because it established that any planet that "has not cleared the neighborhood around its orbit, and is not a satellite" would fall under a different classification. It was decided by a group of only 424 astronomers and immediately became a hotly-debated issue. Astronomers at the University of Central Florida in Orlando reviewed scientific literature dating back to 1801 and found that the only reference to an orbit-clearing prerequisite was over 215 years ago, and the argument for it has since been disproven. "The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research," said UCF planetary scientist Philip Metzger. He added that – if the IAU's definition were to be honored – then, technically, there would be no planets in our solar system. "They didn't say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit."

Metzger and his team argue that the true definition of what makes a planet was established by Gerard Kuiper in the 1950s and has to do with how the celestial bodies are formed, not whether or not they clear the orbit of a neighboring planet. Kuiper's definition makes the distinction between planets and things like asteroids – which, at one point in history, were inaccurately called planets. "We suggest attempts to build consensus around planetary taxonomy not rely on the non-scientific process of voting, but rather through precedent set in scientific literature and discourse, by which perspectives evolve with additional observations and information, just as they did in the case of asteroids," read the closing line of the new study's abstract. Moving forward, Metzger and his team say that planets should be called planets if they are large enough to made spherical by their own gravity. "And that's not just an arbitrary definition," the astronomer said. "It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body."

So let's all welcome Pluto back to the family – although, for some of us, she never left.

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