Defining Pluto as a planet again!

Posted March 23, 2017

Giving this age-old scientific and astronomic debate a new twist and fresh angle, a team of scientists, led by Kirby Runyon from Johns Hopkins University has filed a lawsuit.

Kirby Runyon, a scientist at Johns Hopkins University in the U.S., says Pluto, along with more than 100 celestial bodies in the solar system, including the moons of Jupiter and Earth, should be awarded the (coveted) planet status.

The Solar System could have way more than just eight planets according to recently proposed criteria.

Runyon and his team said that instead, planetary classification should focus on defining characteristics like atmosphere and landscape, and should be organized in a hierarchy similar to that of life on earth. Even more, he says that a host of moons (including Europa and the Moon) and other bodies (like these guys here) in the Solar System should be planets, too. According to Runyon, a planet is, "a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters".

"There's a teachable moment here for the public in terms of scientific literacy and in terms of how scientists do science", Runyon added.

In 2006, Pluto was declared not a real planet but a dwarf planet.

Runyon and his co-authors are all associated with NASA's New Horizons mission, which returned the first high-quality images of Pluto in 2015 after a close flyby as the spacecraft continued toward the Kuiper Belt. That portion of IAU's 2006 formula - which required that a planet and its satellites move alone through their orbit - excluded Pluto.

The new definition differs from the three-element IAU definition in that it makes no reference to the celestial body's surroundings.

The key differences between the IAU and Stern definitions is that Stern's planets do not need to orbit a star, nor do they need to "clear their neighborhood".

The visual simulation, posted to Reddit by user Nobillitie, shows the orbits of all eight planets in our Solar System - Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune - as well as thousands of dwarf planets beyond.

Astronomers "may find the IAU definition perfectly useful", but "our geophysical definition is more useful for planetary geoscience practitioners, educators and students". And that whopping increase is actually a good thing, Runyon says, as he thinks it will engage the public in space exploration.

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.