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Celebrating Pluto's pals

An artist's conception shows NASA's New Horizons probe passing over Pluto in 2015.

Three years ago today, NASA's New Horizons probe set off on a mission for Pluto and other little worlds on the edge of the solar system. On the same day, little Hana and Nora Fennell set off on a mission of their own.

The twin daughters of Alan Fennell and Risha Raven were born on this day in 2006. Since then, New Horizons' managers at Johns Hopkins University's Applied Physics Laboratory have enlisted Hana and Nora - along with four other kids who mark Jan. 19 as their birthday - as "Pluto Pals."

The mission's top scientist, Alan Stern, said the idea came to him when he saw a newspaper picture of two boys watching the New Horizons launch. "It made me think it would be fun to follow some children who would grow up during our 9½-year trip to Pluto," he said.

Hana and Nora's grandfather, Patrick O'Connor III, played a big role in getting the idea off the ground. He recalled watching the launch over the Internet from his office at DeVry University's Chicago campus, and hearing later in the day that his daughter was in labor. O'Connor, who was dean of electronics and computer technology, said in an e-mail message that both of the day's events made a big impression on him:

"Since I am a great fan of spaceflight in all its aspects, a year later, I sent a 'congratulations' to Alan Stern at NASA, noting the anniversary of the launch was, coincidentally, a 35th birthday for a son-in-law, the first birthday for my two twin granddaughters, the birthday of Allen Steele (one of my favorite science fiction writers) and the birthday of Robert E. Lee. Alan Stern wrote back about the 'Pluto Pals' idea, and I let Risha know her twins might be 'mascots' for the New Horizons mission.

"The twins, Hana and Nora, were born in Northern Illinois, about 80 miles from Streator, where [Pluto discoverer] Clyde Tombaugh was born. With the Pluto/Charon system being a double planet, I thought it was fitting that two sets of twins were among the Pluto Pals.

"She submitted their names and I thought their selection was one of the coolest things ever.  They will probably appreciate the 'NASA swag' they were sent when they get a little older, but they're only 3, and New Horizons is in hibernation mode now - not very exciting at the moment.

"By the time of arrival July 14, 2015, at Pluto/Charon, they'll be old enough to appreciate it, I hope."

Fennell and Raven are a husband-and-wife team on the Illinois farm (where they tend a blog as well as livestock), and Raven also serves as the family practitioner in Polo, Ill. (pop. 2,500). It's a busy life, but Fennell said they make sure to take the time to answer their kids' questions about science - whether it has to do with the workings of a tractor battery or the name of a star cluster in the night sky.

Courtesy of Patrick J. O'Connor III
Nora and Hana Fennell were born on the same

day that NASA's New Horizons probe was launched

toward Pluto, in 2006. They'll be 9 years old when

the probe finally reaches the icy world.

"Science is important to us as a family, and teaching opportunities are important. ... There's nothing like that teaching moment. That only comes around one time," Fennell told me.

What to call Pluto serves as another teaching moment: After New Horizons was launched, the International Astronomical Union voted to classify it as a "dwarf planet" rather than a major planet. That vote sparked a controversy that is still working itself out. (More on that next week.)

Hana and Nora aren't in on the debate yet, but other members of their family have been. "I asked their 12-year-old sister what she thought," Raven told me. "She said she's been told that Pluto was not a planet, and she really doesn't understand why."

By the time Hana and Nora celebrate their 10th birthday, we should know a lot more about Pluto and its place in the solar system - thanks to another 10-year-old zooming billions of miles away.

To learn more about New Horizons on its birthday, check out the three-year update on the mission Web site. You can look back at New Horizons' eye-opening Jupiter flyby in 2007, and this handy-dandy dashboard will show you where the spacecraft is from now until at least 2015.