LAS CRUCES, N.M. —  Size doesn't matter. That was the message as friends and colleagues of the late Clyde Tombaugh, the astronomer who discovered Pluto, gathered on the New Mexico State University campus to protest the International Astronomical Union's recent decision to strip Pluto of its status as a planet.

About 50 students and staff members turned out Friday for the good-natured challenge. Some were wearing T-shirts and carrying signs that read "Protest for Pluto" and "Size Doesn't Matter."

Tombaugh's widow, Patricia, and their son, Al Tombaugh, also participated.

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NMSU astronomer Bernie McNamara told the crowd that textbooks shouldn't be rewritten.

"Why not? Because the debate is not over," McNamara said.

The IAU determined last week that a planet must orbit the sun and be large enough to assume a nearly round shape, as well as "clear the neighborhood around its orbit." Pluto's oblong orbit overlaps Neptune's, which led the IAU to downsize the solar system to eight planets from the traditional nine.

McNamara argued that only about 400 of the union's thousands of members were present when the Aug. 24 vote was taken.

"This was not a statement by the astronomical community at large," he said, adding that a petition opposing the IAU definition of a planet is circulating among the world's planetary scientists and astronomers.

Tombaugh was 24 when he discovered Pluto while working at Lowell Observatory in Flagstaff, Ariz., in 1930. He came to NMSU in 1955 and founded the school's research astronomy department.

His legacy is visible across the city, where an observatory, a campus street and an elementary school bear his name.

Some say Tombaugh's discovery was significant because it took 60 years for stronger telescopes to locate another object with an unusual orbit like Pluto's, and 73 years before scientists discovered a bigger object in the area.

"Clyde Tombaugh was an American hero," said Herb Beebe, a longtime colleague. "For that reason alone, Pluto's status as a full-fledged planet should be kept."