“The problem in the past was that although we had the word ‘planet,’ we didn’t have a quantitative definition of it.” Brett Gladman arXiv IAU General Assembly
Without a quantitative standard, the current definition runs into a lot of problems, Gladman said. Specifically, the criteria are vague and it’s unclear how big these objects have to be or “how distinct” their orbits have to be to be considered planets. For example, Earth and Jupiter are asteroid Cross their path regularly Exoplanets Solar System .
But “the biggest problem is the roundness standard.” Jean-Luc Margot
Related: Giant planet discovered around small star could upend our understanding of how the solar system formed
Instead of focusing on a planet’s roundness or orbit, the new definition emphasizes a measurable quantity: the mass of an object. The new definition defines a planet as a celestial body that meets the following criteria:
To ensure their classification framework was logical and unbiased, the scientists used a technique called unsupervised clustering, an algorithm that groups similar objects together. This technique: Solar System
“Whatever criticisms one may have of the current IAU definition, we can at least be persuaded that the resulting classification of eight planets is valid,” he said.
Astronomers are looking at the ability to clear orbits, the so-called Dynamic Advantage
Dynamic advantage also Mass Lower Limit
Regarding sphericity, the mass of an object larger than 10^21 kg is Typically spherical
“Humans are so tied to language and names and classifications because that’s how we think about the world,” Gladman added. “It’s how we organize the complexity of the world. We want to name things and classify them, and scientists want to do that too. We want to do that accurately.”
There’s always the possibility of opposition: Margot plans to present the proposal at the IAU General Assembly in August, but he doesn’t expect there to be consensus. Rather, he hopes that through the presentation, the team will identify people who are interested in the idea and that the discussion will continue.
The proposal was written out of “a conviction that we can do better as a community,” Margot said, and “we owe it to ourselves and the public to come up with better definitions for these important astrophysical terms.”
