Could tiny Pluto circle back to planet status? KU astronomer hopes so

photo by: Associated Press

This image made available by NASA on July 24, 2015 shows a combination of images captured by the New Horizons spacecraft with enhanced colors to show differences in the composition and texture of Pluto's surface. (NASA/JHUAPL/SwRI via AP)

Pluto could get an upgrade in the planetary scheme, but it will take several rotations around the sun before that happens.

A scientific journal recently reported that Pluto should never have been downgraded to a dwarf planet in 2006. News of an upgrade would make fans of University of Kansas alumnus Clyde Tombaugh happy.

Tombaugh, from tiny Burdett in western Kansas, was a 24-year-old amateur astronomer when he discovered the ninth planet in our solar system in 1930.

It was after this discovery, which brought him worldwide acclaim, that he enrolled at KU.

Clyde Tombaugh poses with this telescope, through which he discovered Pluto, at the Lowell Observatory on Observatory Hill in Flagstaff, Ariz.

The latest research, published in Icarus, a scholarly journal, in August, reported that Pluto should have never been demoted. According to the authors, the rationale behind the decision wasn’t sound.

The news validates what Bruce Twarog, a KU professor in the department of physics and astronomy, has always felt about Pluto’s downgrade.

“I believe that the majority, but not all, of the scientists involved in solar system/planetary research have always felt that the original downgrade was unjustified and that the rationale used to explain it was inherently flawed,” he said.

“The change was made by a small number of astronomers, the majority not planetary scientists, at the end of an IAU (International Astronomical Union) meeting where the IAU General Assembly rejected the recommendation of its own panel of experts who had produced a more cogent classification, one which kept Pluto as a planet,” Twarog said.

According to IAU, a planet is a “celestial body that orbits the sun, has sufficient mass for its self-gravity to overcome rigid body forces, is nearly round in shape and has cleared the neighborhood around its orbit.”

What’s in dispute about Pluto is the last part of the definition. The IAU thought Pluto was too small to “clear the neighborhood,” which refers to the ability to move other rocks out of its path as it orbits the sun, but many scientists disagree.

The status of Pluto remains an element of interest and concern in KU’s department of physics and astronomy because of its strong ties to Tombaugh.

“Any revision which places Pluto back where it belongs among the other planets is welcome,” Twarog said.

However, the classification should be left to the experts involved in the day-to-day research on planets, Twarog said.

He offers his views with a caveat.

“Clearly, I have a totally nonscientific bias in favor of the old designation,” Twarog said.

The decision to upgrade would be made by the IAU, the governing professional organization in astronomy/astrophysics.

“It operates through a variety of commissions and working groups, each with its own area of specialization. There is a Working Group on Planetary System Nomenclature within the IAU, which deals with naming and classifying objects within the solar system. I believe this is the appropriate one for this case,” Twarog said.

One would need to submit a proposal to redefine “planet” and, if it makes it past the Working Group, it would likely go to a vote of the IAU General Assembly again, Twarog said. However, the assembly has already met for 2018 and won’t meet again until 2021.

“To the best of my knowledge, no proposal has been submitted to the IAU to revise the definition of a planet, but that could change in the future,” Twarog said.


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