When astronomers demoted Pluto to “dwarf planet” in 2006, New Mexico declined to go along quietly.

The reason was personal. Clyde Tombaugh, who discovered Pluto in 1930, spent much of his life in New Mexico and taught astronomy at New Mexico State University. In 2007, the state legislature honored him with an unusual declaration: whenever Pluto passes overhead through New Mexico’s night skies, it is to be declared a planet.

The measure also proclaimed March 13, 2007, “Pluto Planet Day.”

Technically, this wasn’t a law. It was a joint memorial, an official expression of the legislature rather than an enforceable statute. But New Mexico wasn’t finished. In 2010, its House of Representatives adopted another memorial declaring that, in honor of Tombaugh, “Pluto will always be considered a planet in New Mexico.”

By the official astronomical definition, Pluto remains a dwarf planet. But in New Mexico, where its discoverer made his home, Pluto is still a planet.