Artist's impression of the hypothetical Planet Nine, a roughly Neptune-mass world that may lie undiscovered in the outer solar system.

Don't call it Planet Nine.

That nickname for the big world that may lurk unseen in the far outer solar system doesn't show the proper amount of respect to the discoverer of the original ninth planet, Pluto, a group of researchers argues in a new message to their colleagues.

The International Astronomical Union (IAU) famously reclassified Pluto as a "dwarf planet" in 2006. That decision remains highly controversial today, as made clear by the new note, which appeared in the July 29 issue of the Planetary Exploration Newsletter.

The message, titled "On the Insensitive Use of the Term 'Planet 9' for Objects Beyond Pluto," reads:

"We the undersigned wish to remind our colleagues that the IAU planet definition adopted in 2006 has been controversial and is far from universally accepted. Given this, and given the incredible accomplishment of the discovery of Pluto, the harbinger of the solar system's third zone — the Kuiper Belt — by planetary astronomer Clyde W. Tombaugh in 1930, we the undersigned believe the use of the term 'Planet 9' for objects beyond Pluto is insensitive to Professor Tombaugh's legacy.

Pluto, as seen by NASA's New Horizons spacecraft during its historic flyby of the dwarf planet in July 2015. (Image credit: NASA/JHUAPL/SwRI)

"We further believe the use of this term should be discontinued in favor of culturally and taxonomically neutral terms for such planets, such as Planet X, Planet Next or Giant Planet Five."

Nearly three dozen researchers signed onto this message. They are:

American astronomer Clyde Tombaugh, who discovered Pluto in 1930. (Image credit: NASA/JPL/Space Science Institute)

Paul Abell

Michael Allison

Nadine Barlow

James Bauer

Gordon Bjoraker

Paul Byrne

Eric Christiansen

Rajani Dhingra

Timothy Dowling

David Dunham

Tony L. Farnham

Harold Geller

Alvero Gonzalez

David Grinspoon

Will Grundy

George Hindman

Kampalayya M. Hiremath

Brian Holler

Stephanie Jarmak

Martin Knapmeyer

Rosaly Lopes

Amy Lovell

Ralph McNutt

Phil Metzger

Sripada Murty

Michael Paul

Kirby Runyon

Ray Russell

John Stansberry

Alan Stern

Mike Summers

Henry Throop

Hal Weaver

Larry Wasserman

Sloane Wiktorowicz

Leonard David is author of "Mars: Our Future on the Red Planet," published by National Geographic. The book is a companion to the National Geographic Channel series "Mars." A longtime writer for Space.com, David has been reporting on the space industry for more than five decades. Follow us @Spacedotcom, Facebook or Google+. This version of the story published on Space.com.