The battle for Pluto’s planetary status continues

There’s been a fierce debate over the past two decades about the status of the distant icy world of Pluto after it was contentiously stripped of its planethood and reclassified as a dwarf planet.

Nasa chief Jared Isaacman has indicated that he might revisit the matter but it won’t be an easy decision because scientists are still “worlds apart” on the issue, said The Observer.

Rock and ice

Pluto was discovered on 18 February 1930 by an American astronomer called Clyde Tombaugh. He was using one of the most powerful telescopes of his day at the Lowell Observatory in Arizona.

For 76 years the “tiny ball of rock and ice” was recognised as the ninth, smallest and most distant planet of the solar system. But in 2006, nine years after Tombaugh died, members of the International Astronomical Union voted on the criteria for a planet.

To qualify, the group decided, an object must orbit the Sun, be nearly round in shape, and be the largest object in its path. Pluto meets the first two conditions but not the third, because it shares its orbit with other icy objects, in a region called the Kuiper Belt. So its status was downgraded to a dwarf planet.

This decision was “controversial” and “not just because it forced schoolchildren” to “learn a new mnemonic for our solar system’s major denizens”, said Space. Earth and Jupiter share orbital space with lots of asteroids, “so why was Pluto singled out?” Pluto was “beloved and remains so”, especially in the US, because “it’s the only planet discovered by an American”.

The “most vocal” Pluto advocate has been the planetary scientist Alan Stern. “Science isn’t about voting,” he said in 2016 of the IAU’s decision. “We don’t vote on the theory of relativity. We don’t vote on evolution.”

There was a “significant escalation” in the pro-Pluto campaign in July 2015, when Nasa’s New Horizons spacecraft produced the “first-ever up-close imagery” of Pluto, revealing a “stunningly diverse world” with “towering mountains, vast nitrogen-ice glaciers and other jaw-dropping features”, said Space. But the “historic flyby” wasn’t enough to “get Pluto its planethood back”.

Maga echoes

But now, Nasa boss Isaacman has signalled that the US space agency might re-examine the case for Pluto to be given its planet status back. Last month, he told a US Senate committee that he was “very much” wanting to make Pluto a planet again. He added that “some papers” were under way at Nasa to “revisit this discussion”.

With an “echo of Maga”, “make Pluto a planet again” is a phrase that suggests a “nostalgic journey back to a past of certainties”, when “everything was in its right place in the heavens”, said The Observer. But “actually it’s the Plutonists who represent the argument for radical change” and Stern has calculated that there might be as many as 1,000 planets in the solar system.

But first, the best thing that Nasa and other “Pluto advocates” can do is “escalate the discussion”, said Space.