LAS CRUCES, N.M. — It's not surprising that the approach of NASA's New Horizons spacecraft to Pluto is one of the best things that ever happened to the family of Clyde Tombaugh, who discovered the dwarf planet back in 1930.
But you might be surprised to hear what else is on his daughter's list of memorable moments: It's the day in 2006 when the International Astronomical Union voted to take Pluto off the list of planets.
"If Pluto had not been demoted, I would probably not be this involved in it," Annette Tombaugh-Sitze, 74, told NBC News. "I would never have gotten involved with the Great Planet Debate. I would never have met Neil Tyson. I would never have done the 'NOVA' show. I would never have met so many wonderful people. And that has been my journey."
Since even before the launch of New Horizons nine years ago, the Tombaugh family's emotional highs and lows have paralleled Pluto's fortunes. Right now, they're on a 3-billion-mile high: The piano-sized New Horizons spacecraft is due to buzz within 8,000 miles of the icy world's surface on July 14. The eyes of the world are on Pluto, and that means they're also on Annette and her brother, Alden Tombaugh.
Annette and Alden are now the senior members of the Tombaugh clan: Clyde died in 1997 in Las Cruces, when the debate about Pluto's planethood was still percolating. His wife, Patsy, lived to see New Horizons launched in 2006 — and see Pluto demoted seven months later.
"I'm not heartbroken," Patsy told reporters at the time. "I'm just shook up." She passed away in 2012 at the age of 99, when New Horizons was flying between the orbits of Uranus and Neptune.
There's a little bit of Clyde Tombaugh on the New Horizons spacecraft. Literally. A smidgen of his cremated remains was placed there before launch, beneath a medallion commemorating his role as "the discoverer of Pluto and the solar system's 'third zone.'"
"My dad would have been thrilled," Alden Tombaugh, 70, told NBC News. "He always said that if he had the chance, he wanted to visit the planets. And a little part of him is going to get to do that."
Both children are living in Las Cruces, where Clyde helped establish New Mexico State University's astronomy program as well as the local Unitarian Universalist church. Annette has spent most of her life as a teacher. Alden had a 37-year career in banking and is now helping his wife with an educational diagnostics business.
Alden also has a side interest in race cars. But how about science? "That type of work never interested me. I think I was too lazy," he joked.
Even though the children didn't follow their father into the field of planetary science, they're both well-versed in the case for keeping Pluto in the planetary fold. Their criticism of the IAU focuses on the part of the definition for planethood that talks about a planet having to "clear the neighborhood around its orbit" — a concept that some professional astronomers have also questioned.
"The problem as I see it is, as we go farther and farther out, and find objects orbiting other stars, what do we call them?" Alden said. "Well, they decided to call them planets, but we have no idea if they are, based on the new definition."
Looking beyond the Pluto connection, both children say one of the things they remember most about their father was his persistence. That trait is what helped Clyde sort through hundreds of photographic plates at the Lowell Observatory back in 1930 — looking for, and ultimately finding, the elusive signature of a new world on the solar system's edge.
"One of the lessons learned from my father's experience is that a dedication to something you enjoy can lead to adventures for all mankind," Alden said.
Now Clyde's children are showing the same kind of dedication to Pluto's cause: New Horizons is once again giving Pluto, and the Tombaughs, their day in the sun.
"This refocuses the interest in a positive fashion," Annette said. "I thought the status would always be, 'Oh, forget Pluto.' ... But as we go through this event, it's going to make people aware that there is a whole other part of the solar system that is highly populated with many more bodies than the original eight, or nine, or 10.
"Getting close to Pluto is going to widen our view of not just our solar system, but the universe."