Group of scientists aim to make Pluto a planet again

Ever since Pluto lost its planet status more than a decade ago, the world has been in mourning.

Runyon proposes that the new draft definition be used for classification of celestial bodies. So, Runyon says, is Europa - commonly known as a moon of Jupiter - and so is the Earth's Moon and so are more than 100 other celestial bodies in our solar system that are denied this status under the prevailing definition of "planet".

Kirby Runyon of Johns Hopkins University headed a six-man team of authors from five different scientific bodies in preparing their own version of how planets should be classified.

Pluto "has everything going on on its surface that you associate with a planet". They will present their findings on March 21 at the conference sponsored by the Lunar and Planetary Institute.

This definition can be paraphrased for school children as a "round objects in space that are smaller than stars".

The definition approved by the International Astronomical Union (IAU) in 2006, demoted Pluto to "non-planet", dropping the number of planets in our solar system from nine to eight. "There's nothing non-planet about it", Runyon said. That ignores numerous "rogue planets".

Researchers argued in the past that IAU definition also excludes Earth, Mars, Jupiter and Neptune, which share their orbits with asteroids.

Perhaps we will now see a dichotomy between how astronomers and geologists define a planet as Runyon's proposal is more useful to planetary scientists and as many are closely affiliated with geology and other geosciences, this new geophysical definition is more useful in these fields than the IAU's astronomical definition. This makes the nine planets of the Solar System to eight. The new geophysical definition does not include stars, asteroids, black holes and meteorites but everything else in solar system is included. The object also has sufficient gravitational mass to keep its round shape although it expands at the equator due to a three-way squeeze of forces generated by its gravity and the impact of the Sun and close-range bigger planet.

The team's definition doesn't require approval from a central governing body for scientists to start using it - in fact, it's already been adopted by Planet Science Research Discoveries, an educational website founded by scientists at the University of Hawaii. The very word "planet" seems to carry a "psychological weight", he adds, so more planets could help pique public curiosity and instill a yearning for exploration in people. "I want the public to fall in love with planetary exploration as I have", said Runyon.

  • Carolyn Briggs