We grew up (okay, “most of us”, don’t remind me about my age) learning that nine planets surround our solar system. But in 2006, Pluto was demoted, classifying it as a dwarf planet instead. Now, a group of scientists once again challenges our previously believed “facts”- they said Pluto should be added back to the planet list and oh, there are over a hundred more!
Kirby Runyon of Johns Hopkins University, together with five authors from different scientific bodies, contended their own version of how planets should be classified
, expanding the number of our planets from the current eight to around 110.
They insist a definition that focuses on the intrinsic qualities of the planet itself, rather than external factors such as its orbit or other objects around it. That is, a celestial body can be considered a planet when the object itself has the quality of being a planet rather than focusing on things like its location. They define a planet as "a sub-stellar mass body that has never undergone nuclear fusion" that has enough gravitational immensity to maintain a roughly round shape. This differs from the three-element IAU definition.
For instance, the exclusion of Pluto is only due to the fact that the planet and its satellites don’t move alone through their orbit. Pluto "has everything going on on its surface that you associate with a planet. ... There's nothing non-planet about it," Runyon said. Even Jupiter’s moon of Europa as well as Earth’s moon would be included as planets with the new description!
He says that the expansion is part of the appeal of the new definition, figuring that the increased number of planets could encourage public interest. "I want the public to fall in love with planetary exploration as I have," he said. "It drives home the point of continued exploration."
This argument and all their supporting information will be on display at the Lunar and Planetary Science Conference in Texas. So, what do you think? Do you agree with Runyon’s (and team) definition? Or do you think we should stick with the old-school classification?