The Jupiter Theft

She shuddered, trying to imagine it. The thing called Cyg X-1 was an X-ray inferno, shedding an invisible glare equal to the total energy output of ten thousand suns. If it had any planets, it had fried them long ago.

Vampire stars—that was what X-ray sources like Cyg X-l generally turned out to be: black holes or neutron stars that circled a blue supergiant companion, relentlessly sucking away its gases. As the gas fell into that terrible gravitational field, it was squeezed, bruised, heated to temperatures of up to 100 million degrees Kelvin. In the process it gave off that raging hellfire of X-rays.

The odds were that the new source in Cygnus would turn out to be something similar. The evolution of such X-ray binaries had been well understood since the late twentieth century: A massive star swelled as it burned up its hydrogen fuel, overflowing its Roche lobe and contributing mass to its companion. A supernova explosion in the burnt-out star left a black hole behind. And then, for a brief period of thirty or forty thousand years, a reversal of the mass exchange as the companion star in turn burned up its hydrogen and bloated to a blue supergiant, while the relentless hole devoured its substance. The Farside computer would be comparing its X-ray and radio images now, trying to fit its accumulating data into such a picture.

Another ping brought her attention back to the board. The junior resident peered over her shoulder.

“The computer’s found something it can’t handle,” he murmured. “It’s just plugged itself in to the data center at Mare Imbrium.”

The two computers, on opposite sides of the Moon, began exchanging data. After a couple of seconds the console buzzed to catch the humans’ attention, and a new request flowed across the screen.

“Now it wants the use of the five-hundred-inch reflector,” the resident said.

The tech bit her lip again. “I’d better get Dr. Ruiz,” she said.

“He won’t like it. He was up all night.”

But the duty tech already had spoken into her lapel communicator and asked the desk to wake up Farside’s director.

By the time Dr. Ruiz arrived, green-smocked technicians and off-duty personnel were milling around the area. Word had spread quickly that something was going on, and curious faces peered into the glass-walled monitor booth.

Ruiz pushed through the crowd and closed the door of the booth behind him. He was a tall, gaunt man, slightly stooped, with hollow cheeks and a leathery complexion. His knobby legs showed the effects of childhood malnourishment. His eyes were bleary with lack of sleep, and he was still tucking his singlet into his baggy shorts.

“I’m sorry, Dr. Ruiz, but—”

He waved her apology aside. “What’s this about the computer asking to divert the Sagan reflector?”

“It’s true, Doctor. It’s already diverted the Polyphemus array. Now it apparently wants to try for a counterpart image at the visible wavelengths. But with optical-viewing time booked three months in advance, I thought I’d better—”

“Yes, yes. You did the right thing to call me.” The director’s eyes already were roving restlessly over the winking lights and flickering data screens of the big board. “What have you got so far?”

The tech turned on her lightpad. Her handwriting and underlinings, in scratches of blue lightning on the pad’s polycrystalline surface, crowded the computer-generated script she had dialed in from the board.

“Well, for one thing it doesn’t pulse. It just gives off a steady X-ray emission consistent with a point source.”

“Hmmm. How about the possibility of sinusoidal variation with a period of several hours, like Cyg X-3?”

She shook her head firmly. “The computer’s been tracking it long enough to have detected a curve. It’s a radio source, too. We have a fix on it with Polyphemus.”

Ruiz raised a shaggy eyebrow. “You diverted Polyphemus?

She stood her ground. “Yes, Doctor. I’m authorized to—”

“Don’t worry about it.” He laughed. “I’ll deal with Dr. Shevchenko. You’re doing fine so far. Go on.”

The junior resident butted in, trying to get himself noticed. “Excuse me, Dr. Ruiz, but the X-ray source is only a couple of seconds of arc from Cyg X-1. It confused the telescope at first. Doesn’t that suggest that it’s been occulted by X-1 until now?”

“And what do you say”—Ruiz squinted at the duty tech’s ident disk—“Mizz Maybury?”

The tech blushed. “It’s only twenty-eight days since the last sighting. Cyg X-1 is over ten thousand light-years away. The new source couldn’t have been hiding behind it. For the apparent separation to increase that much, it would have to be moving laterally at several hundred times the speed of light.”

“And what does that suggest?”

Maybury gave the junior resident an apologetic glance. “That it’s the other way around. The new source may have been masked by Cyg X-l, but it’s closer to the solar system.”

“My thought exactly.”