We photographed the star dozens of times. We checked our instruments ceaselessly. I spent hours scanning the star's "official" spectrum in the microspool reader. The bright emission line was not on the catalogue spectrum. There was nothing wrong with our instruments.
Yet the bright line showed up. It was real.
"I don't understand it," I admitted. "I've seen stars with bright emission spectra before, but a single bright line in an absorption spectrum! It's unheard-of. One single wavelength ... one particular type of atom at one precise energy-level ... why? Why is it emitting energy when the other wavelengths aren't?"
Rizzo was sitting on his bunk, puffing a cigaret. He blew a cloud of smoke at the low ceiling. "Maybe it's one of those laser signals you were telling me about a couple weeks ago."
I scowled at him. "Come on, now. I'm serious. This thing has me puzzled."
"Now wait a minute ... you're the one who said radio astronomers were straining their ears for nothing. You're the one who said we ought to be looking. So look!" He was enjoying his revenge.
I shook my head, and turned back to the meteorological equipment.
But Rizzo wouldn't let up. "Suppose there's an intelligent race living on a planet near a Cepheid variable star. They figure that any other intelligent creatures would have astronomers who'd be curious about their star, right? So they send out a laser signal that matches the star's pulsations. When you look at the star, you see their signal. What's more logical?"
"All right," I groused. "You've had your joke...."
"Tell you what," he insisted. "Let's put that one wavelength into an oscilloscope and see if a definite signal comes out. Maybe it'll spell out 'Take me to your leader' or something."