Pluto’s finder’s legacy in trouble

Newly found UB313 bigger than planet discovered by Kansan

On the eve of his 100th birthday, Clyde Tombaugh’s big discovery is in danger of being diminished.

Tombaugh, of course, is the Kansan who discovered Pluto in 1930. He died in 1997, but the scientific dispute about Pluto’s status – whether it deserves to be labeled a “planet” – is picking up steam.

“Attempts in the past to reclassify Pluto have met with opposition from the scientific community and from the public,” said Barbara Anthony-Twarog, a Kansas University professor who is helping lead this weekend’s Lawrence celebration of Tombaugh’s centennial.

But the issue got more complicated this week. Scientists reported that UB313 – an icy, rocky body out on the edge of the solar system – is actually bigger than Pluto, which some critics have suggested is too small to be a planet.

Either both are planets, some scientists say, or neither is.

“Since UB313 is decidedly larger than Pluto, it is now increasingly hard to justify calling Pluto a planet if UB313 is not also given this status,” Frank Bertoldi, an astronomer at the Max Planck Institute for Radioastronomy in Bonn, Germany, said in the journal Nature, which reported the findings.

Tombaugh, who grew up on a farm near the western Kansas town of Burdett, discovered Pluto on Feb. 18, 1930, while working at the Lowell Observatory near Flagstaff, Ariz. He was only 24 at the time.

He decided he needed a college degree to make his mark in astronomy, and KU recruited him to Lawrence. Tombaugh received his bachelor’s degree in 1936 and his master’s degree in 1939.

Bertoldi led a research team that measured surface temperatures of UB313 to confirm that this “ice dwarf,” more than 9 billion miles from the sun at its farthest point, is about 1,800 miles in diameter, whereas Pluto’s diameter is about 1,380 miles.

Neither one is “big.” Earth’s moon is 2,160 miles in diameter.

Some scientists believe Pluto should be upheld, but others suggest that Pluto, UB313 and other icy denizens of the Kuiper Belt beyond Neptune are not planets but “objects.” There is no clear leader in the debate.

There is no official definition of “planet,” making the matter more complicated. Anthony-Twarog defends Pluto’s status, but said, “Pluto’s got a foot in both camps, scientifically.”

While the debate rages, KU will celebrate. Saturday would’ve been Tombaugh’s 100th birthday, and the university plans a telescope viewing of the night sky, as well as a talk by Alan Stern, a scientist participating in the New Horizons satellite mission to Pluto.

For now, at least, Pluto is a planet at KU.

“We have our position,” Anthony-Twarog said. “We like to remind our students about this important part of KU astronomy history.”