A quick confirmation
After lunch on the day of the discovery, Christy settled into a routine measuring job for about 10 minutes before it dawned on him that the odds of a background star interfering at the exact time of observation were minuscule. It had to be a moon.
Next, the astronomer started digging up old photographic plates of Pluto. He found the same elongation in images from 1970 and 1965. Harrington told Christy to measure the position angles of his moon while he calculated an orbit based on the light variations seen in both the old and new images.
“We didn’t contact each other until we were both done, and we compared the opposition angles of his predictions and my measurements, and they were all right on six plates in a three-day period, which was amazing,” Christy says.
Even more amazing, Christy says he had been convinced the astronomers in Flagstaff had overexposed their images of Pluto in the past when he requested his observations. He asked them to halve their usual 4-minute exposure period. And while the astronomers gathered Christy’s images much later than expected, they happened to observe Pluto at the ideal time of year and perfect position in the sky.
The USNO contacted a colleague in Chile and received confirmation that there was indeed an elongation on Pluto at the point Christy and Harrington predicted. So, the observatory announced its find to the world July 8, 1978.
Pluto and Oz?
As discoverer, Christy earned the naming rights to Pluto’s companion. He and Charlene were driving to her parents’ wedding anniversary when they started chatting about what to call it. His first choice was Oz. Then, he thought he could name it for his wife. Physicists were constantly finding new particles in those days and naming them by simply adding “‘on” to the end of their chosen word. So, he concocted “Charon.”
When he went to the observatory, the other astronomers had already come up with Persephone, Pluto the god’s wife. Christy says he thought their suggestion was so good it was automatic, and he went off to move into his new home with help from the guys at the observatory.
“We got moved into the house, and there was no power in the house, so we had no refrigeration or lights, and when we finished up, it was about 10 o’clock at night and I was totally exhausted,” Christy says. “I went to sleep immediately, and then a strange thing happened — I think the strangest thing in my life. About right after midnight, I woke up I was thinking ‘In the morning, I have to tell Charlene that I can’t name the moon after her.’”
He says that he got up, half asleep, and stumbled through the house with a flashlight looking for the boxes of books.
“I found the dictionary and opened it up, and it said Charon, and in Greek mythology the boatman that sails across the river Hades into the domain of Pluto, and I said ‘OK,’ and I just staggered back to bed.”
He reluctantly told the crew of his decision and the rest is history. To honor Charlene, astronomers now pronounce the moon like “Sharon” instead of the traditional Greek pronunciation, which sounds more like “Karen.”
Christy says he still likes Oz.
"That would go along with Hollywood Pluto, and it would have been great for kids," he says. "I think that would have been a better choice. I think of all the kids who learn about Pluto and Oz, and there would be a lot of imagination, since nobody would ever see it.”
Harrington, who is often credited as Charon’s co-discoverer for his role in the find, had married James and Charlene’s friend, Betty-Jean Maycock, who actually introduced the Christys. The Harringtons named their daughter Ann Charon.
Bob Harrington died tragically of cancer at the age of 51 in 1993. Christy left the USNO in 1982 so he could return to Arizona. He ultimately retired early in Flagstaff, where he still lives.
What does he expect to see when New Horizons reveals his moon for the first time next month?
“I have no ideas,” he says. “I hope it’s a big surprise and not a flat gray ball.”
Eric Betz is an associate editor of
Astronomy. He's on Twitter:
@ericbetz.