Is Pluto a planet? It is, according to NASA Administrator Jared Isaacman, who said as much during a hearing held by the House Appropriations Subcommittee on Commerce, Justice, Science, and Related Agencies to review NASA's Fiscal Year 2027 budget request on Monday.

“I am very much in the camp of ‘make Pluto a planet again,’ and I would say we are doing some papers right now on a position that we would love to escalate through the scientific community to revisit this discussion,” he said in response to a question from Republican Sen. Jerry Moran.

Pluto is a dwarf planet in the Kuiper belt, a ring of icy objects beyond the orbit of Neptune. NASA’s New Horizons mission conducted a flyby of Pluto in 2015, taking the first and only images of its surface.

Pluto’s Discovery — And Demotion

Discovered on Feb. 18, 1930, by astronomer Clyde Tombaugh at Lowell Observatory in Flagstaff, Arizona, the object, 5 billion miles from Earth, had spent over 76 years as the solar system’s ninth planet. It remains the ninth-largest object to orbit the sun, though only just.

The end of its tenure was announced on Aug. 24, 2006, by the International Astronomical Union — a group of astronomers, not planetary scientists — when it issued Resolution B5 that redefined what constitutes a planet in the solar system.

Nowadays, Pluto is called a dwarf planet or (the largest) trans-Neptunian object, and there are only eight planets in the solar system — Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

It wasn’t Pluto’s fault. It’s a story plagued by ever-changing nomenclature and the discovery of other large objects, but at its heart is that new definition.

Officially, Pluto is not a planet because it has not cleared its neighboring region of other objects. As of 2006, to get planet status, an object must meet these three criteria:

  • It is in orbit around the sun.
  • It has sufficient mass to assume hydrostatic equilibrium (a nearly round shape).
  • It has “cleared the neighborhood” around its orbit.

Pluto meets the first two criteria, but fails the third. Some planetary scientists argue the definition is flawed and should be revised. Many simply refer to Pluto as a world, therefore dodging the controversy.

Why A Planet Had To Be Redefined

In 2003, American astronomer Michael Brown discovered Sedna, then the most distant object ever found in the solar system. That distinction now goes to a planetoid nicknamed Farfarout (2018 AG37), which was found in 2021.

Sedna was the first of a series of distant objects discovered, including almost Pluto-sized Haumea, Makemake and Eris, which eventually prompted the International Astronomical Union to revoke Pluto's full planet status. The alternative would have been to call about 20 different objects planets.

Isaacman also said that he would like to “ensure that Clyde Tombaugh gets the credit he received once and rightfully deserves to receive again.”

Wishing you clear skies and wide eyes.