Sic Transit Gloria Pluto

And then there were eight …

Leading astronomers declared Thursday that Pluto is no longer a planet under historic new guidelines that downsize the solar system from nine planets to eight.After a tumultuous week of clashing over the essence of the cosmos, the International Astronomical Union stripped Pluto of the planetary status it has held since its discovery in 1930. The new definition of what is — and isn’t — a planet fills a centuries-old black
hole for scientists who have labored since Copernicus without one.

[… Pluto] 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.

It was unclear how Pluto’s demotion might affect the mission of NASA’s New Horizons spacecraft, which earlier this year began a 91/2-year journey to the oddball object to unearth more of its secrets.

It’s profiling, I tell you! Planetary profiling!

Now, two of the objects that at one point were cruising toward possible full-fledged planethood will join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it got demoted, and 2003 UB313, an icy object slightly larger than Pluto whose discoverer, Michael Brown of the California Institute of Technology, has nicknamed “Xena.”

Charon, the largest of Pluto’s three moons, is no longer under consideration for any special designation.

Well, until the next IAU meeting, at least.