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.'"

Re:Let it go

[john83]

Actually, our own moon is a planet according to their definition - it's over 3000 km across. As I understand it, it's not currently classified as one because the earth-moon system's centre of gravity is inside the earth.

Bad Astronomy, Bad Taxonomy

[syousef]

I for one couldn't care less what category Pluto falls under. Planet, Dwarf Planet, Pototoid, Potato Chip. Who cares. I have no emotional attachment.

What I do care about is bad science and bad classification. The current definition stinks. The problems I have

1. A 'dwarf planet' is not a subclass of 'planet' as one would expect from the name. It should have been named something different.
2. The definitions refers to our the sun. Not the star which the planet orbits but 'the sun'. That makes it sound like extrasolar planets are not planets either.
3. The definition of planet requires that the body has cleared it's orbit. So while it is forming early in the solar system it is not a planet then one day "poof" by magic we have a planet.
4. The draft proposal was nothing like the final proposal. The definition was passed on the last day of that IAU conference when lots of scientists had already gone. That suggests a political pissing match rather than well thought out science.
5. The definition is not consistent with what had been taught for decades, and there was no good reason for that.

I have an Astronomy degree that I did for fun and that I have never used professionally. I lost all respect for the IAU on the day they released their crappy definition.