On Aug 24th in Prague, Czech Republic, the ninth plante in our solar system – Pluto – was demoted to a new category of called “dwarf planet” at the 6th convention of the International Astronomical Union (IAU). The new classification to which the icy ex-planet Pluto is now relegated will potentially have dozens of members.
At the convention, 2,500 scientists participated in the now-famous vote, which is responsible for Pluto’s new status.
The newly-adopted definition establishes three conditions that an object must meet in order to be considered a planet: 1) its path must be clear of debris and other objects, 2) it must orbit around the sun, and 3) it must be have a round shape.
The vote was not only to establish Pluto’s place in the universe, but also to meet the need for a stricter definition of planets. It was deemed necessary since new telescope technologies have lately revealed far -off objects rivaling Pluto in size. It had become difficult to catagorize these other objects since, being similar in composition and size to Pluto, they would then have to be included in our solar system.
According to the new definition, new objects discovered by the Hubble Telescope will have to be noted and classified as dwarf-planets if they cannot qualify as planets.
Dr. Richard Soare, MSc in geomorphology, has been leading field expeditions for the past 4 years in the Arctic with his students to study mars-related geomorphology (the study of landforms, their origins and the processes that shape them). He is a lecturer at Concordia and had this to say about the vote: “All that’s happened,” he stated in an interview, “is that a new classification came along. Before, there used to be no boundaries.”
“As they discovered Xena (also known as 2003 UB313), they decided to call it a planet simply because it was bigger than Pluto. Then they found Ceres (was) big enough to be called a planet as well and there simply was no way to draw the line.”
Ceres and Sedna (previously referred to as “the tenth planet” in 2004) and Charon are classified along with Pluto as “dwarf planets”.
He goes on to recall how Ceres, discovered in 1801, also went through a similar debate in the 19th century. Initially called a planet, it also got stripped of its status after the discovery of the asteroid belt between Mars and Jupiter. The term then adopted for Ceres was “asteroid” and at the same time, three other “planets” got demoted.
“It is simply about classification, almost semantics,” he commented.
From Soare’s point of view, the demotion of Pluto makes sense: the planets closer to the sun (Mercury, Venus, Earth, Mars) are rocky, and the planets further away (Jupiter, Saturn, Uranus, Neptune) are all gas planets. The only exception is Pluto, itself a solid mass of earth and ice.
The other planets also have paths that are all clear of other big objects, whereas Pluto’s orbit overlaps with that of Neptune, failing to dominate its orbit around the sun as do the other planets. Refer to diagram