The Jupiter Theft

The wait was over an hour. There could be no such thing as a conversation with Mars, particularly when Mars was on the other side of the Sun, as it was now. As the crow flies, it would take radio waves a bit more than twenty minutes to travel one way. But the crow would not fly through the sun. The message had to be bounced off the relay satellite orbiting Venus, currently a quarter orbit ahead of Earth, and in line of sight with both Earth and Mars. The round trip for an exchange of messages, with the detour, would take about an hour, even if Larrabee answered immediately.

He answered almost immediately. Ruiz was into his third cup of lukewarm coffee when Larrabee’s voice came out of the wall, clear as a bell, with all the interplanetary static edited out by the computer. Voice transmissions from Mars were sent in pulse-code modulation with triple redundancy, and in the unlikely event that any particular pulse was wiped out all three times, the gap was too infinitesimal for the human ear to detect.

“I don’t know what this is all about, Hernando,” a cheerful baritone said, “but I’ll take your word for it that it’s important. We’re zeroing in on your Cygnus source now. Just sit tight a couple more minutes. I’ll keep the beam open. You owe me a drink when I get back.”

Ruiz sipped another cup while the resident, Kerry, hovered around him and Maybury punched setups into the board. The new shift had arrived, and they were tiptoeing around, trying not to look curious. Ten minutes later, lights started blinking all over the board as the Mars computer fed data via radio into the Farside computer’s memory buffer register. The computer, consulting its hydrogen maser clock, corrected for transmission delay.

Before astronomers had set up shop on Mars, they had had to wait six months to measure parallax. You took a picture of your target star, and when the Earth had traveled halfway around the sun you took another picture on the same plate and measured the apparent shift. Now you could triangulate by taking sightings from the Moon and Mars simultaneously.

Ruiz watched the figures unreeling on the LED displays, his coffee forgotten. In his mind he translated them into a triangle with a base line that was 234 million miles wide. If the X-ray source was anywhere within a hundred light-years, he’d get reliable results.

Two glowing dots appeared on the viewplate against a background of stars; the computer had enough data now to attempt a preliminary visualization. Who had asked it to do that? He looked up—that technician, Maybury. She was efficient. That fool with the shaved chest was doing nothing except stand around looking important.

Ruiz looked back at the screen and blinked. The dots had stopped jiggling. They were impossibly far apart. The parallactic shift was … huge!

The damned thing was less than a light-year away!

He snatched the lightpad from a startled Mizz Maybury and made his own rough calculation. His answer approximated the computer’s average figure: a distance of about half a light-year. The Cygnus source was close—closer than any stellar object had a right to be. And it wa blue-shifting. And there was no proper motion. All the motion was head-on.

Something soft nudged his arm: Mizz Maybury’s breast. She was leaning across him, thrusting a piece of paper in front of him, trying to get his attention.

“Dr. Ruiz!” she said urgently. “I thought you might want—that is—I asked the computer to pull out the most recent planetary data. The positions of the outer planets—I mean, there’s a discrepancy of several seconds in the longitude and declination of both Neptune and Pluto. It might turn out to be simple observational error, but—-”

He waved her aside. “In a moment, Mizz Maybury.” He was staring intently at the screen that showed the values for the base angles. The computer was constantly updating them as it refined and reaveraged its data. They held steady up to the eighth decimal point, then jumped back and forth a good deal, but the trend of the figures was definitely higher.

The thing had to be moving fast to show any noticeable change in that short a time. Ruiz was almost afraid to ask how fast. But he wiped the lightpad and scribbled an order for the computer to pin a tentative value on the blue shift and try to correlate it with the changing parallax. There was a pause of several seconds while the computer searched its peripheral memories for an appropriate program; then figures began to flow across the lightpad, while a duplicate column of numbers marched across one of the display screens.

He heard a gasp behind him. Maybury was looking over his shoulder.

“That’s right,” he said. “It appears to be moving toward us at something more than ninety-eight percent of the speed of light.”

Over at the data screen the junior resident cleared his throat. He was perspiring, and the green ident disk on his chest was coming unstuck. “That means it’ll be in the vicinity of the solar system in about six months,” he said.