Contact - Carl Sagan [29]
"But then the transmitter power has to be ridiculously large," responded a member of the quasar group who had returned to see what was happening. "We need to get going right away on a sensitive proper motion study, so we can see if the radio source moves with Vega."
"Of course, you're right about the proper motion, Jack," she said. "But there's another possibility. Maybe they didn't grow up in the Vega system. Maybe they're just visiting."
"That's no good either. The system is full of debris. It's a failed solar system or solar system still in its early stages of development. If they stay very long, their spacecraft'll be clobbered."
"So they only arrived recently. Or they vaporize incoming meteorites. Or they take evasive action if there's a piece of debris on a collision trajectory. Or they're not in the ring plane but in polar orbit, so they minimize their encounters with the debris. There's a million possibilities. But you're absolutely right; we don't have to guess whether the source is in the Vega system. We can actually find out. How long will that proper motion study take? By the way, Steve, this isn't your shift. At least tell Consuela you're going to be late for dinner."
Willie, who had been talking on the phone at an adjacent console, was displaying a wan smile. "Well, I got through to a Major Braintree at NORAD. He swears up and down they have nothing that'll give this signal, especially not at nine gigahertz. 'Course, they tell us that every time we call. Anyway, he says they haven't detected any spacecraft at the right ascension and declination of Vega."
"What about darks?"
By this time there were many "dark" satellites with low radar cross sections, designed to orbit Earth unannounced and undetected until an hour of need. Then they would serve as backups for launch detection or communications in a nuclear war, in case the first-line military satellites dedicated to these purposes were suddenly missing in action. Occasionally a dark would be detected by one of the major astronomical radar systems. All nations would deny that the object belonged to them, and breathless speculation would erupt that an extraterrestrial spacecraft had been detected in Earth orbit. As the Millennium approached, the UFO cults were thriving again.
"Interferometry now rules out a Molniya-type orbit, Dr. Arroway."
"Better and better. Now let's take a closer look at those moving pulses. Assuming that this is binary arithmetic, has anybody converted it into base ten? Do we know what the sequence of numbers is? Okay, here, we can do it in our heads… fifty-nine, sixty-one, sixty-seven… seventy-one… Aren't these all prime numbers?"
A little buzz of excitement circulated through the control room. Ellie's own face momentarily revealed a flutter of something deeply felt, but this was quickly replaced by a sobriety, a fear of being carried away, an apprehension about appearing foolish, unscientific.
"Okay, let's see if I can do another quick summary. I'll do it in the simplest language. Please check if I've missed anything. We have an extremely strong, not very monochromatic signal. Immediately outside the bandpass of this signal there are no other frequencies reporting anything besides noise. The signal is linearly polarized, as if it's being broadcast by a radio telescope. The signal is around nine gigahertz, near the minimum in the galactic radio noise background. It's the right kind of frequency for anyone who wants to be heard over a big distance. We've confirmed sidereal motion of the source, so it's moving as if it's up there among the stars and not from some local transmitter. NORAD tells us that they don't detect any satellites- ours or anybody else's-that match the position of this source. Interferometry excludes a source in Earth orbit anyway.
"Steve has now looked at the data outside the automated mode, and it doesn't seem to be a program that somebody with a warped sense of humor put into the computer. The region of the sky we're looking at includes Vega, which is an A-zero main sequence dwarf star. It's