Charles Sheffield - Aftermath

By that time, Alpha Centauri had brightened by seventeen magnitudes. Celine gave the blazing point of light on the display one glance, noted its still-increasing intensity, and immediately buzzed Zoe.

“Zo? You there? We’ve got something I think you’ll want to take a look at.”

“What?” Zoe Nash was the head of the Mars expedition, and she sounded half-asleep. It was a rare condition for her, but in this phase of the flight home lethargy seemed more virtue than vice.

“It’s Alpha Centauri,” Celine said. “It’s superbrilliant. I think it’s becoming a nova, even a supernova. More than a thousand times as bright as usual.”

“Really?” Zoe became more lively. “I do want to take a look at that. Everyone else will, too. Make a general announcement, will you?”

“Sure.”

Celine alerted the ship’s general intercom, made sure that the scope would remain locked on Alpha Centauri, and headed aft. The ship had been designed with high redundancy, so that any one of its three sections could at a pinch become a stand-alone unit able to make the journey home. A much overcrowded journey, to be sure, and one with little margin for error if all seven expedition members were present; but the crew would reach Earth orbit alive. The price paid for that triple security was the difficulty of transition from one section to the next. Celine grumbled to herself as she squeezed through a narrow passage with an airlock at each end. Small-boned and thin as she was, it was still hard going. When she reached the observation chamber at the far end of the ship’s third section, every other expedition member was already there.

She surveyed the group, wondering where to place herself. In the front row, pushing each other for extra space, were Zoe Nash, Wilmer Oldfield, and the chief geologist — and areologist — Reza Armani. Behind them were the other three crew members, Alta Mclntosh-Mohammad, Ludwig Holter, and computer specialist Jenny Kopal. Celine had hardly seen them all in one place since the return ship left the surface of Mars.

Reza in particular had almost disappeared, gloating over his collection of Mars samples like a demented miser. Celine worried sometimes about his attitude, he seemed close to irrational on the subject. True, five of the samples did contain dormant bacterial life-forms of enormous interest. Wilmer Oldfield and Celine herself had performed the genome scans. The forms were DNA-based, but their sequences were nothing remotely like any Earth organism. Reza had stood by all through the work, glowering at Celine and Wilmer as though they might attempt theft of his treasure.

The observation chamber had not been designed to accommodate all the team at once. Celine was not going to get the best viewing position, no matter what she did. She squeezed in, peered over Alta McIntosh-Mohammad’s shoulder, and gasped. Direct observation was quite different from looking at something on a screen. There was no question which star was Alpha Centauri. Although still showing only as a white point of light, it was brilliant enough to cast shadows inside the chamber.

“It looks brighter than it did just a few minutes ago,” she said.

“It is.” Wilmer recognized her voice and spoke without looking around. “Celine, did you get a reading for a number of magnitudes increase?”

His accent was the strongest in the whole international group. He was Australian, and he had bemused Celine at their first meeting by insisting that what he spoke was standard English.

“Yes, I did,” she said. “It was seventeen, when I last looked.”

“Then if it’s a supernova — which I think it may be, even though it shouldn’t — it’s just getting going.”

“What do you mean, shouldn’t?” Zoe Nash was a short and stocky woman of mixed Ugandan and Turkish descent. She was right where an expedition leader ought to be, up at the front of the group. She was also, because of the shortage of space, squashed by the others against the observation window.

“Alpha Centauri is a double-star system,” Wilmer said, in his relaxed drawl. “Double stars can become a Type la supernova, but only if one of the two stars is a white dwarf. Alpha Centauri doesn’t qualify.”

“Then I guess Alpha Centauri doesn’t know that,” said Zoe. “It’s not a good day to be an astronomical theorist. Hey, give me some air, folks.” She wriggled around to face Wilmer Oldfield. “What do you mean, just getting going?”

“If this is a supernova, the increase in brightness will be as much as a hundred billion. We are still far short of that.”

“Are we going to be safe?”

Celine listened for Wilmer’s answer with special interest. In addition to being in charge of instrumentation, she was also the expedition’s physician. The medical supplies and equipment were adequate for “normal” emergencies, but a supernova didn’t qualify.

“Safe?” Wilmer blinked his eyes and rubbed his stubbly beard as though such a question had never occurred to him. Celine’s guess was that it hadn’t. He was a super scientist and a sweetheart, but sometimes he seemed on a different wavelength from normal people.

“I dunno,” he said after a moment. “But I can work it out easy enough. The bigger star of Alpha Centauri is pretty much a look-alike for our sun, same spectral type but a little bit brighter. It’s about one and a third parsecs away, so that’s about two hundred seventy thousand times as far as the sun is from Earth. If it becomes a hundred billion times as bright as usual, it will look a hundred billion divided by two hundred seventy thousand squared as bright as the sun. So there you are.”

He paused, as though that was the end of the story. “Translation, Jenny,” said Zoe. “Do the calculation, would you, for people like me. How bright will it be?”

“One hundred billion divided by two hundred seventy thousand squared is one point thirty-seven.” Jenny Kopal was in charge of computers, and the common view was that she had a personal one inside her head. Celine found it easier to ask the dark-haired Hungarian for the answer to calculations rather than keying it in herself.

“That’s bright,” Reza said. He giggled. “Sell Sunscreen 100, you’ll make your fortune.”

“Well, that could be off a factor of two, one way or the other,” Wilmer added. “But Reza’s right, Alpha Centauri as seen from Earth will be bright, maybe as bright as the sun. Of course, that’s only for a month or two, then it goes dim again.”

Except for Wilmer, the group in front of Celine moved in concert, edging away from the chamber window.

“Are we in danger?” Zoe asked.

Wilmer shrugged. He had the long limbs and wide shoulders of an outdoorsman. That, combined with his Australian accent, had Celine in the first months of their acquaintance expecting him to talk about wombats and wallabies rather than quantum field theories. “I don’t see why,” he said at last. “We can handle solar radiation. We have the inner shielded area in Section One, in case of big solar flares.” He looked thoughtful. “Course, when the gas shell of the supernova expands, a big slug of gamma rays will break out. We have no idea which direction they’ll emerge. But we have enough shielding to handle that, too. The big problem is going to be the high-energy particle flux. That will carry a lot more energy than the visible light or the gamma rays. It’ll be an absolute killer.”

Zoe came bolt upright. “And you say we’re not in danger!”

“We’re not. The light and gammas travel at light speed, but the particles are much slower — five to ten percent of light speed. It will take them fifty years to get here.”

The group relaxed again.

“Fifty years,” Zoe said. “I don’t care about fifty years. I was worried about fifty minutes or fifty hours.”