NASA Chief Jared Isaacman Urges Pluto’s Return as 9th Planet

Q: If top scientists still can't agree, is Pluto's status as a planet more a matter of opinion than scientific fact?

Pluto’s status is not a matter of opinion in the sense that scientists disagree about the facts; it is a matter of scientific definition, and that definition is still debated. The underlying observations are well established. Pluto orbits the sun, is nearly round, has a thin atmosphere, and shows complex geology, as NASA’s New Horizons mission demonstrated. Scientists also agree that Pluto shares its orbital zone with many Kuiper Belt objects and does not dominate its neighborhood the way the eight larger planets do. The dispute is over which traits should define a planet. Under the International Astronomical Union’s 2006 definition, a planet must orbit the sun, be round, and have cleared its orbital neighborhood. Pluto fails that third test, so officially it is a dwarf planet. That is the current formal standard used by the IAU. But many planetary scientists argue that this is too narrow. They favor a geophysical definition based on what an object is physically like, not where it sits dynamically. By that standard, Pluto would qualify as a planet, along with some other dwarf planets and possibly some large moons. Alan Stern of the New Horizons mission has long argued this view, while astronomers such as Mike Brown support the IAU’s narrower definition. So Pluto’s classification is best understood as a real scientific disagreement over categories, not over data. The facts about Pluto are solid; the label depends on which scientifically defensible definition is used.

2 articles · Updated · Space.com · Jul 1

Jared Isaacman said Pluto should again be considered a planet, putting NASA’s administrator behind a renewed push to revisit the solar system’s official count of eight.
The dispute turns on the International Astronomical Union’s 2006 definition, which demoted Pluto because it had not “cleared the neighborhood” around its orbit beyond Neptune.
Discoveries of many trans-Neptunian objects in the 1990s and Pluto’s placement in the Kuiper Belt drove that reclassification, while NASA’s 2015 New Horizons flyby strengthened arguments that Pluto is a complex geologic world.
The broader debate remains unresolved between scientists favoring a dynamical definition of planets and those backing a geophysical one, leaving open whether future findings could restore Pluto as the 9th planet.