TrendWagon: Is Pluto a Planet? Vote Now!

Pluto was discovered in February 1930, making this month its 80th anniversary. Unfortunately, Pluto is not in such a festive mood as its status was downgraded in 2006 from a fully blown planet to a mere dwarf planet. This is a bit like telling one of your kids that sadly they were adopted and therefore have been left out of the family will. However, the rumblings over a solid definition of a planet have continued to this day, and some people want Pluto back into our family of planets - at which point we could upgrade all the other dwarf planets to full status.

So what defines a planet anyway? Well, I'm going to write a longer article on this very soon, but the thing that got Pluto downgraded is that its orbit not only overlaps with Neptune but is also in a different plane to the other eight major planets. Strangely, NASA still has Pluto in its own planet category and hasn't placed it alongside the other dwarf planets, or planetoids.

Anyway, do you think Pluto should be a planet? You can vote on it during February.

The above image (courtesy of NASA) shows the Earth and Moon, with Pluto and one of its moons (Charon) at the bottom, plus Eris and Ceres (both dwarf planets, with Eris being slightly larger than Pluto). The image is to scale. Thus, if Pluto is a planet then so is Eris. Ceres could be a planet but it hasn't cleared its orbit of all the other asteroids. For the moment, all 3 are dwarf planets.

2 comments:

Anonymous15 February 2010 at 18:03
Pluto is still a planet. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. One reason the IAU definition makes no sense is it says dwarf planets are not planets at all! That is like saying a grizzly bear is not a bear, and it is inconsistent with the use of the term “dwarf” in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. Also, the IAU definition classifies objects solely by where they are while ignoring what they are. If Earth were in Pluto’s orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless. Pluto is a planet because it is spherical, meaning it is large enough to be pulled into a round shape by its own gravity--a state known as hydrostatic equilibrium and characteristic of planets, not of shapeless asteroids held together by chemical bonds. These reasons are why many astronomers, lay people, and educators are either ignoring the demotion entirely or working to get it overturned.
Unknown15 February 2010 at 18:40
On the point about that vote, that's surely what happens when votes are taken at meetings rather than by the wider membership?

Here's a link to their original press release: http://www.iau.org/public_press/news/detail/iau0603/

My feeling is that they are trying to make the nomenclature fit the current theory of planetary development. Thus it may look and smell like a planet but its orbit makes it likely that it gatecrashed the family gathering. However, I think they've made a mess of it. Under this logic then, a satellite that was previously an asteroid is no longer a legitimate satellite but some kind of "captured asteroid" class of object.

The whole thing makes it look as if there is a solid theory as to how planets formed and how they got to where they now are, which just isn't the case.

I agree with you, I'm just thinking through what was in their minds at the time! Thanks for the comment.