The Grim Fate of Pluto

Pluto is the ninth planet of our solar system, the smallest and the farthest. No, wait, it's not a planet anymore. Trouble never seems to end for this little fellow, after the "embarrassment" of being degraded to a lower rank.

The former planet has been dissed again. As it turns out, it's not even the biggest in the new class of dwarf planets it's been degraded to, it's just the second in command. Yet another indignity for a small guy that's been with us for a few centuries and has now been ditched.

"This is sort of Pluto's last stand," joked Emily L. Schaller of California Institute of Technology, co-author of a report presented by the International Astronomical Union, who last year redefined the classification of planets and created a new subcategory of dwarf planets, among which Pluto was thought to be the largest.

After calculating the movement of Dysnomia, a moon of another dwarf planet, Eris, astronomers came to the conclusion that Eris is the largest known dwarf planet in the solar system and the ninth largest body orbiting the Sun directly, being 1.27 times the mass of Pluto, formerly the largest member of the Kuiper Belt of icy space objects beyond Neptune.

Not only is Eris heavier than Pluto, but it's also slightly physically larger, having a density of 2.3 grams per cubic centimeter, very similar to the density of Pluto.

Eris's moon, Dysnomia, was born out of a collision between Eris and another Kuiper Belt object, and the satellites of Pluto, as well as the Earth-Moon system are also believed to have been born out of a collision process where debris from the smashup goes into orbit and coalesces into a satellite.

The trouble for Pluto started in 1995, when astronomers discovered Eris, and realized it was around the same size as Pluto, if not larger, and realized they would have to call it the "10th" planet if Pluto retained its own planetary status. So, it's now just a dwarf planet smaller than another dwarf...