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.'"

Comments

Proper nomenclature

[BadAnalogyGuy]

The preferred term is size-challenged planets.

Pluto is pissed

[tpstigers]

And is forming a gang. We could be in big trouble here.

The gang shall be called

[spun]

Snowy cold and the several dwarfs.

nobody tosses a dwarf planet off the list

[jollyreaper]

Plutoids ain't got no reason to live.

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.

Better name

[jlebrech]

Just name them potato planets.

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.

Re:Bad Astronomy, Bad Taxonomy

[dkleinsc]

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.

Re:Bad Astronomy, Bad Taxonomy

[John Hasler]

What was foolish was attempting to come up with an algorithmic definition of planet instead of accepting that a planet (in our solar system) is any one of the nine objects on the list of planets.

Re:Let it go

[Theuberelite]

A dwarf planet must "not be a satellite of another planet" so our moon does not count as a dwarf planet according to the IAU.

Re:Demotion?

[reverseengineer]

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.

In space, no one can hear you sing.

[moviepig.com]

Dwarf Planets Accumulate In Outer Solar System

"Heigh-ho, heigh-ho..."

Re:Let it go

[Nadaka]

The moon does not orbit the earth, nor the sun. The earth doesn't orbit the sun for that matter.

The earth/moon system orbits its barycenter and that barycenter, the sun and barycenter of the other planet systems orbit the combined barycenter of the solar system.

I am technically correct, and that is the best type of correct.

Re:Let it go

[Red Flayer]

Shame on you for not recognizing a Futurama reference. Please surrender your geek card immediately

Aw, crap. Please, can I get an exception this one time? Please?

I've been a little busy building and programming my fleshy robot companion, so I'm behind a couple seasons on watching Futurama and other nerd canon.

I promise I'll get caught up as soon as I get the hip actuators working properly.