Scientists against the demotion of objects like Pluto, Eris, Sedna, etc. to "dwarf planet" status have crafted a new definition:
It's no secret that Alan Stern and other scientists who led the New Horizons mission were extremely displeased by Pluto's demotion from planet status in 2006 during a general assembly of the International Astronomical Union. They felt the IAU decision undermined the scientific and public value of their dramatic flyby mission to the former ninth planet of the Solar System.
But now the positively peeved Pluto people have a plan. Stern and several colleagues have proposed a new definition for planethood. In technical terms, the proposal redefines planethood by saying, "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters." More simply, the definition can be stated as, "round objects in space that are smaller than stars."
From the proposal:
The eight planets recognized by the IAU are often modified by the adjectives "terrestrial," "giant," and "ice giant," yet no one would state that a giant planet is not a planet. Yet, the IAU does not consider dwarf planets to be planets. We eschew this inconsistency. Thus, dwarf planets and moon planets such as Ceres, Pluto, Charon, and Earth's Moon are "fullfledged" planets. This seems especially true in light of these planets' complex geology and geophysics. While the degree of internal differentiation of a given world is geologically interesting, we do not use it as a criterion for planethood in the spirit of having an expansive rather than a narrow definition.
Here's another article about the significance of the New Horizons mission. New Horizons will fly by 2014 MU69 on January 1, 2019.
(Score: 0) by Anonymous Coward on Wednesday February 22 2017, @02:56PM
It's easier to get funding to study the farthest (sometimes farthest, actually) planet in the solar system than some remote iceball.
It's purely marketing.
(Score: 2) by takyon on Wednesday February 22 2017, @03:05PM
The marketing was already done by Disney. Lack of a planetary status doesn't make Pluto any less well-known. In fact, losing the status made Pluto, Michael E. Brown, and Neil deGrasse Tyson better known (cha-ching).
Finding more of the TNOs probably helped make New Horizons possible. From the second article:
As for other TNOs with good marketing, that would be Planet Nine, Eris, and maybe Sedna. Although you don't need marketing to want to prioritize the discovery and study of a possible gas giant.
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