So, it has been asked, here and other places, how do I feel about the Pluto thing?

Here’s the actual text of the resolutions:

IAU Resolution:  Definition of a Planet in the Solar System
Contemporary observations are changing our understanding of planetary
systems, and it is important that our nomenclature for objects reflect
our current understanding. This applies, in particular, to the
designation ‘planets’. The word ‘planet’ originally described
‘wanderers’ that were known only as moving lights in the sky. Recent
discoveries lead us to create a new definition, which we can make using
currently available scientific information.

RESOLUTION  5A
The IAU therefore resolves that "planets" and other bodies in our Solar
System be defined into three distinct categories in the following way:

(1) A "planet"¹ is a celestial body that (a) is in
orbit around the Sun, (b) has sufficient mass for its self-gravity to
overcome rigid body forces so that it assumes a hydrostatic equilibrium
(nearly round) shape, and (c) has cleared the neighbourhood around its
orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around
the Sun, (b) has sufficient mass for its
self-gravity to overcome rigid
body forces so that it assumes a hydrostatic equilibrium (nearly round)
shape² , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects³  except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".

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¹The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

²An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
³These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

IAU Resolution:  Pluto

RESOLUTION 6A
The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as
the prototype of a new category of trans-Neptunian objects.

I think this is the correct thing to do. Why? Well, planets have "always" been there, right? Well, no. The ancients knew of Mercury, Venus, Mars, Jupiter and Saturn. You needed telescopes to find Uranus and Neptune and Pluto was calculated to exist by many astronomers based on the movements of the larger planets. It was later found with a telescope and photographic plates by Clyde Tombaugh

So for years, we have been taught, these are the planets…Okay, so why change it now?

Pluto has NEVER fit in as a planet. It’s small. It’s orbit crosses Neptune’s. It’s a rocky planet where the other outer planets are gaseous. Why? Because fundamentally, it is a different type of object.

If you accept, scientifically, Pluto as a planet (as in one of the 8), then any object LARGER than Pluto would fit too, right? That’s why the papers were reporting a 12 planet solar system last week.
Science is a system of classification, study, experiment. I would have loved to keep Pluto as a planet, but it isn’t really. To be scientific, and the IAU is a scientific body, you have to let go of sentiment and go with the science.

So now we have a few dwarf planets. Not a big deal. A rose by any other name is still a rose, right? We haven’t diminished the fact that the telescope and photography, two wonderful inventions, allowed the discovery of this dwarf planet. And others have been found as the detection methods have gotten more sensitive over the years.

If I was an IAU member, I would have voted for this resolution. Let the planets be based on science, not emotions.

For the record, Dr. Jay was home at this point and did NOT cast a vote.