MELVILLE, N.Y. — Pluto, a distant world on the frigid outskirts of the solar system, was downgraded eight years ago when scientists changed its status from full-fledged planet to planetary dwarf.

Scores of Pluto fans booed the decision and terminology – dwarf planet – imposed by the International Astronomical Union, which voted in Prague to reduce the number of planets to eight.

Controversy has yet to wane. There’s a Facebook page devoted to reinstating Pluto. Elsewhere, a permanent online petition still invites the public to voice disagreement with the union. And the editor of a popular astronomy magazine is calling for a presidential-style debate to settle Pluto’s status in the heavens – once and for all.

The maelstrom mounts as Earthlings prepare for a first-ever rendezvous: An American data-gathering spacecraft will make a historic Pluto flyby next year. Ironically, the New Horizon space probe was launched the year the far-flung orb was demoted.

The spacecraft will hurtle breathtakingly close to the Plutonian surface, having traveled seven years and 4.5 billion miles to reach Pluto, deep in the icy Kuiper belt.

Astronomers are certain new insights will emerge from the mission, but that probably won’t change Pluto’s status, they say.

“Clearly, Pluto is a touchy subject,” said Fred Walter, a professor of astronomy at Stony Brook University.

As Walter sees it, powerful scientific evidence undergirded Pluto’s downgrade from planet to dwarf.

“It has the most extreme orbit of any of the planets, at least when it was a planet,” Walter said, noting Pluto, about the size of Earth’s moon, is highly dependent on a larger, full-fledged celestial body, a guardian planet in the cosmos.

“Pluto isn’t gravitationally independent,” Walter added. “It’s gravitationally tied to Neptune.”

But just as mystery has shrouded Pluto because of its multibillion-mile distance from Earth, semantics have affected it, too, Walter said.

“We haven’t really fully demoted Pluto. The word ‘planet’ is still there,” he said, referring to the term dwarf planet.

“But if you were Pluto,” he asked, “would you rather be the runt among planets, or the king of the dwarf planets?”

Another name for Pluto, Walter added, is trans-Neptunian object.

Denton Ebel, who chairs the Earth and Planetary Sciences Department at the American Museum of Natural History in Manhattan, cringes at the thought of “the Pluto discussion.”

Discord, he asserted, is inevitable when the subject is Pluto. He doesn’t think it’s a full-fledged planet, either.

He scoffs at Pluto proponents who say scientists are prejudiced just because it’s small. “It’s not in the same class of objects as Earth and Mars and the other bodies we think of as planets,” Ebel said. “There’s an object in the Kuiper belt that is larger than Pluto, and it isn’t a planet.

“There are lots of objects out there and we are still finding new ones. But everything can’t be a planet.”

Nonetheless, Pluto’s ban from the solar system still stokes powerful emotions in legions of fans.

“In my heart, I know that it really can’t be a planet anymore,” said Ken Spencer, an amateur astronomer and president of the Astronomical Society of Long Island.

“I was really sad to see it demoted. But after reading why, it’s hard to argue with those reasons.”