Make Pluto a planet again.
According to a new study published in the scientific journal Icarus, Pluto never should have been downgraded more than a decade ago.
Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union, which ruled a planet a “celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,and has cleared the neighborhood around its orbit.”
That last qualification is where Pluto was tripped up; the IAU said the planet was too small to control its own orbit, as its gravity is influenced by Neptune’s.
But the new study, led by Philip Metzger, a planetary scientist at the University of Central Florida, argued that because only one study from the past 200 years — a publication written in 1802 — included rules about cleaning orbits, the IAU’s classification was faulty.
“It’s a sloppy definition,” he said in a statement on UCF’s website. “They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.”
Instead, Metzger suggested planets be classified on whether the body is large enough that “its gravity allows it to become spherical in shape.”
“And that’s not just an arbitrary definition,” he said. “It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body.”
Pluto, he said, includes an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons. In fact, he said, the only planet more complex than Pluto is Earth, which has always been a planet.
The IAU has not yet responded to Metzger’s suggestion.
