The Jupiter Theft

She showed her horse’s teeth. “Because,” she said triumphantly, “after six million years they would be socialists!”

Ruiz appeared to ponder the matter. “How do you know they’re not?” he said finally.

“No!” she spat. “They are degenerate society!”

“I should think so,” Ruiz said, “after six million years in their circumstances.”

“Six million years is impossible!” Tu insisted.

Maggie nudged Jameson. “I don’t follow her logic. Either they’ve been around long enough to become degenerate, or they’ve been around long enough to be socialists.”

“Don’t bother about the logic, Maggie,” Jameson said. “It’s just her way of getting across to the troops that the Cygnans are no longer their socialist buddies from the stars. We’re having a change of line.

“But why?”

“Comrades don’t lock the chosen up in a cage. They can’t communicate with the Cygnans, and they know it now.” He frowned. “I wonder if they’re planning some kind of action.”

“They are not travel for six million years,” Tu was screaming. “You tell them, Comrade Chu!”

The Chinese astronomer had been standing off to one side, going over figures on the lightpad with Maybury. He stirred uneasily and said: “You see, Comrade Tu, the interval of time—”

“Tell them, tell them!”

Dr. Chu looked unhappy. “Of course there is always the possibility of error in Dr. Ruiz’s computations, bu—”

Unexpectedly, Captain Hsieh broke in. His round face was stern, his short stocky body stretched to full height. “We must listen to Dr. Ruiz,” he said. “He has learned an important thing about the hsing-ch’ung.” The word he’d chosen meant, literally, “star-worms.” “We must try to understand, so that we may act correctly.”

“What’s happening?” Maggie whispered.

Jameson said, “There’s some kind of shift in power going on. We’re a long way from New Peking. I think Captain Hsieh and his supporters have decided they’re never going to see it again.”

People’s Deputy Commander Yao Hu-fang spoke out from the crowd. “Go ahead, Dr. Ruiz. We would like to hear you.”

Ruiz nodded at him. He waited until the tumult died down. Tu Jue-chen wormed her way through the milling crowd and went off to sulk.

“Comrade Tu is right, in a sense,” Ruiz said, watching her go. “The Cygnans haven’t been traveling six million years. They left six million years ago.”

Dr. Chu put down the lightpad, took a nervous glance at Captain Hsieh for reassurance, and said: “We can be sure about the figures. You see, after the supernova explosion it would have taken the system another six million years to become an X-ray source. The X-ray stage is brief. It could not last more than fifty thousand years. But we know that Cygnus X-1 is an X-ray source now!”

“Or has been within the last ten thousand years,” Ruiz said.

“Of course,” Chu said apologetically. “It is ten thousand light-years away.”

“Go on, Dr. Chu,” Ruiz said. “You’re doing fine.”

“When the helium star exploded, its remnant collapsed. It became a black hole. Cygnus X-1, in fact, was the first black hole to be positively identified, back in the twentieth century. Now, the black hole continued to circle its companion—waiting, as Dr. Ruiz might say, for a chance to take back its stolen mass. “It must wait for six million years, till its companion burns up its ill-gotten hydrogen and becomes a blue supergiant. Blue supergiants are almost always associated with such X-ray sources. A blue supergiant some—oh, twenty times larger than the sun will begin to lose mass in the form of a solar wind, at the rate of about a millionth of a solar mass per year. Some of the mass falls into the black hole. It disappears from the universe forever. But during that fall to infinity, the gas accelerates to tremendous speed, and is heated to a temperature of tens of millions of degrees Kelvin. It is this envelope of falling gas that generates X-rays. For a brief period—not more than fifty thousand years—it will shed X-rays burning with the radiance of ten thousand suns.”

Chu stopped and mopped his brow. His eyes roved toward Hsieh, then to the People’s Deputy Commander.

“After that,” Ruiz said, “the newly formed blue supergiant overflows its Roche lobe and pours its mass down the black hole at a rate that extinguishes it as an X-ray source.”

Mike Berry was facing the two astronomers, hands on hips. “So you say our six-legged friends left home six million years ago, before all this happened?”

“There’s no doubt of it,” Ruiz said.

“Then tell me this—if Cygnus X-1 is ten thousand light-years away, and they’ve been traveling at the speed of light, where have they been all this time?”

Ruiz looked pleased at the question.

“That’s obvious,” he said. “Making stops.”

Mike was a very bright person. He chewed it over a few moments, then said: “Dr. Ruiz. You’ve deduced a hell of a lot about our little buddies from the mass of a star and the mass of a black hole. Now this ought to give us a clue about how long—”

“It does,” Ruiz said.

Boyle got to his feet. “Dr. Ruiz, I think—”