A team of scientists is proposing our definition of a planet. This could mean that Pluto, which was previously the solar system’s 9th planet, may be restored to its former rank.
Scientists led by Alan Stern, head investigator of NASA’s New Horizons mission to Pluto, have submitted a proposal to the International Astronomical Union that aims to change traits a planet must have to be considered as one. Apparently, Stern had to gather a lot of data before submitting the proposal to the Union.
“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,” the proposal states.
In other words, planets can now be all round objects smaller than the stars. Science Alert has also summarized the proposal’s criticism for the current definition of what a planet should be. According to new guidelines, “First, it recognizes as planets only those objects orbiting our Sun, not those orbiting other stars or orbiting freely in the galaxy as ‘rogue planets’,” they explain.
Second, the fact that it requires zone-clearing means “no planet in our Solar System” can satisfy the criteria, since a number of small cosmic bodies are constantly flying through planetary orbits – including Earth’s. Finally, and “most severely”, they say, this zone-clearing stipulation means the mathematics used to confirm if a cosmic body is actually a planet must be distance-dependent because a “zone” must be clarified. This would require progressively larger objects in each successive zone, and “even an Earth-sized object in the Kuiper Belt would not clear its zone”
However, others have pointed out that a lot of space objects actually meet the team’s definition. These objects include the planets, the moons and even the objects situated in the Kuiper Belt.
Others have also pointed out that this would mean that students have now to memorize so many planets. But Stern asserts that memorizing innumerable planets should not be a priority for the students. The most important thing is that they understand them.
“Understanding the natural organization of the Solar System is much more informative than rote memorization,” the proposal also adds. “Teaching the zones of the Solar System from the Sun outward and the types of planets and small bodies in each is perhaps the best approach.”