If you are paying attention enough to know that we’ve got 11 planets now, instead of 9, then you know that the traditional mnemonic for memorizing the order of the planets has become obsolete. The old one (“My Very Excellent Mother Just Sent Us Nine Pizzas” or variants thereof) no longer works now that we have two newly-acknowledged members of the family. Ceres, formerly an asteroid, has been promoted to dwarf planet, joining the humbled Pluto as well as Eris, the outermost planet. Incidentally, Eris wins the best-named moon award for its satellite Dysnomia, which wasn’t even discovered until 2005.
So now we have 8 regular planets and 3 dwarf planets. Now, what is a dwarf planet? According to Wikipedia,
A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but which has not cleared its neighbouring region of planetesimals and is not a satellite. More explicitly, it has to have sufficient mass for its self-gravity to overcome rigid body forces in order to assume a hydrostatic equilibrium and acquire a near-spherical shape.
Some scientists suggest there might be at least 42 and up to maybe 200 objects in the solar system that might be classified as dwarf planets. So if you happen to be cold chillin’ (literally) in the Kuiper Belt, make sure to check out Pluto, Eris and Dysnomia, while a visit to the asteroid belt definitely should involve a trip to Ceres.
Which brings us back to the Montana girl. Maryn Smith, 10, of Great Falls came up with the winning entry to the National Geographic Children’s Books contest: “My Very Exciting Magic Carpet Just Sailed Under Nine Palace Elephants.” Congrats Maryn!
