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Dwarf Planets Accumulate In Outer Solar System
An anonymous reader tips a piece in Australian Geographic indicating that Pluto may be in for another demotion, as researchers work to define dwarf planets more exactly. "[Australian researchers] now argue that the radius which defines a dwarf planet should instead be from 200–300 km, depending on whether the object is made of ice or rock. They base their smaller radius on the limit at which objects naturally form a spherical rather than potato-like shape because of 'self-gravity.' Icy objects less than 200 km (or rocky objects less than 300 km) across are likely to be potato shapes, while objects larger than this are spherical. ... They call this limit the 'potato radius' ... [One researcher is quoted] 'I have no problem with there being hundreds of dwarf planets eventually.'"
It wouldn't be demoted in terms of moving out of its present category. I think the sense is more that the class of dwarf planets, which now comprise only five known objects (Ceres, Pluto, Haumea, Makemake, and Eris) would admit many more members if the minimum radius necessary for the category were revised far downward. The argument then is that the category would be somehow less "special" if there were hundreds or thousands of dwarf planets instead of a handful.
At least from an aesthetic viewpoint, I actually like this proposed new definition though- the size at which an object forms a spherical shape under its own gravity seems like a significant transition. I feel that if an icy sphere the size of Enceladus were discovered out in the Kuiper belt, an assignation of "dwarf planet" would be logical, but such an object would be considered too small under the current IAU definition.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
I'm fairly certain the 'dwarf planet' classification was so-named because it was a foolish compromise with those who wanted to believe that Pluto was still a planet, because they'd been taught for generations that there were 9 planets. If I remember correctly, changing Ceres from being a planet to an asteroid to a dwarf planet wasn't anywhere near as controversial.
I am officially gone from