Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again.
However, I cannot find an official source for this. Is this actually true?
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Yes, Pluto is still a dwarf planet. According to the IAU website, it still fits the criteria for a dwarf planet, fails to meet the criteria for a planet, and still carries the "dwarf planet" label, whatever its future status may be. I'm sorry I can't provide a longer or more detailed answer, but this is really a yes-or-no question.
A lot of the push to have Pluto reinstated as the 9th planet is coming from Harvard, from their press release Is Pluto a Planet? The Votes Are In (Released September, 2014), they state the following outcomes from a debate:
Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU's viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the exoplanet scientist's viewpoint.
Gingerich argued that "a planet is a culturally defined word that changes over time," and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as "the smallest spherical lump of matter that formed around stars or stellar remnants," which means Pluto is a planet.
We will have a better understanding of Pluto, hence its classification when NASA's Horizons mission reaches it. But, at this stage, Pluto is still classified as a dwarf planet.
The 3rd requirement for a celestial object to be a planet is that it has to "clear its neighborhood" which means it has to be gravitationally dominant. Pluto has not enough mass to interact with other object in its orbit(consuming them or swinging them away) and it is only 0.07 times the mass of the other objects in its orbit. Earth is 1.7 million times the mass of other objects in its orbit.
Currently, Pluto is very much a dwarf planet. I don't think Pluto will ever be reinstated as a planet again . . . On the the pro-planet side, Pluto has five moons, which can possibly qualify it as a planet. On the no-planet side, Pluto has a mass of 1.30900 × 10^22 kilograms, which is much lower than the currently smallest planet, Mercury, which weighs 3.285 x 10^23 kilograms. Also, the diameter of Mercury is 4,879.4 km across, while Pluto’s diameter is 2,360 km across. Big difference. Really. I'm pretty sure Pluto won't be called a planet again, but I can't be certain.
Pluto will continue to be exactly Pluto no matter how we choose to categorize it. Fretting about the "proper" category is the tyranny of the discontinuous mind.
Only the International Astronomical Union (IAU) has the mandate to decide what is or is not a planet or a dwarf planet. Or, as Keith Thompson rightfully pointed out, about what the word “planet” and the expression “dwarf planet” mean in English.
The IAU holds a General Assembly every three years. The next one is schedule for August 2024 (in Cape Town, South Africa). I doubt the issue of Pluto will be at the agenda, despite popular media claims and complaints by multiple professional astronomers.
In the end, astronomers can call anything they want a "planet". However, some form of distinction should be made between objects that clear their neighborhoods and those that do not. Clearing the neighborhood is a major structural feature of our Solar System, for it leads to the small bodies that make up most of the Solar System's population being largely confusing to specific belts and zones.
Earth is one of a select group objects responsible for that, and so is Mercury. Pluto and Ceres cannot really be their equals no matter what words we choose as labels.
Moons Are Planets: Scientific Usefulness Versus Cultural Teleology in the Taxonomy of Planetary Science is a 2021 paper that outlines a thesis that: