Holy moly, the sacred tenent from our childhood science classes, "My Very Eager Mother Just Served Us Nine Pickles," must be revised to something like "My Very Evasive Mouse Just Scared Us Now" as the International Astronomical Union has officially decided that Pluto in not a planet. They took a vote and everything! From the AP:

For now, membership [of the planets] will be restricted to the eight ''classical'' planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Much-maligned Pluto doesn't make the grade under the new rules for a planet: ''a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.''

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.

Instead, it will be reclassified in a new category of ''dwarf planets,'' similar to what long have been termed ''minor planets.'' The definition also lays out a third class of lesser objects that orbit the sun -- ''small solar system bodies,'' a term that will apply to numerous asteroids, comets and other natural satellites.

And when they made the announcement, they used a Pluto plush - as in Mickey Mouse's dog - to illustrate the point!

Michael Brown, the Cal Tech astronomer who discovered the so-called "tenth planet" Xena, is happy about the decision, even though it means Xena is put in the dwarf planet category; check out his website for some interesting background on planet sizes. The IAU's website is inaccessible, probably because everyone wants to know all about the decision. And if you're interested in experiencing the stars, head to the American Museum of Natural History's Rose Center, where the Hayden Planetarium is. Now, we're going to do the "corn starch in water" experiment before someone tells us that liquids and solids are no longer states of matter.

Photograph of the IAU's Richard Binze, Christopher Corbally and Jocelyn Bell-Burnell by Petr David Josek/AP