Ring

This star was no more than a couple of million years old. But already — to her intense regret — she’d missed one of the most interesting phases of its existence.

The star had formed as a ball of fusing hydrogen, two thousand times more massive than the Sun. There had been convection cells then, too, which had driven instabilities in the giant star; it had breathed, swelling and contracting through fully a tenth of its diameter in a day. The instabilities had grown, exponentially, resulting at last in the casting off of huge shells of material from the surface of the star, like a series of repeated nova explosions; the Northern had sailed in through those ancient shells, on its way to its orbit around the new sun.

Meanwhile, the helium core had grown, and steadily contracted, and heated up.

At last, the core reached half the mass of the original VMO — about a thousand Solar masses. And a shell of hydrogen around the core ignited.

The mass of three Suns was flashed to energy within mere hours — expending energy that could have fueled Sol for ten billion years of steady burning. The wind from the explosion stripped off the still-fusing envelope, creating another expanding shell around a remnant helium star.

Now, as Lieserl flew through the star, the helium was in turn burning to oxygen, which was being deposited in the star’s core. Eventually, the oxygen would ignite. And then -

And then, the outcome wasn’t certain. Her processors were still working on predictions: gathering data, developing scenarios. It all depended on critical values of the star’s mass. If the mass was low enough the star could survive, for many millions of years, its diameter oscillating slowly… and rather dully, Lieserl thought. But a little larger and the star could destroy itself in a supernova explosion — or, if massive enough, collapse into a black hole.

Lieserl studied the data streams trickling into her awareness. She would know soon. She felt a shiver of excitement. If the star was unstable, the end would come well within a million years. And then -

…Lieserl?

The voice of Louise Ye Armonk broke into her thoughts. Damn. Lieserl lifted her arms over her head and plunged into a huge convection fountain; the fusing star stuff played over her Virtual body, warming her to the core.

But she couldn’t escape Louise’s voice, any more than she’d been able to outrun Kevan Scholes.

Come on, Lieserl. I know you can hear me. I’m monitoring your data feeds, remember —

Lieserl sighed. “All right, Louise. Yes, I can hear you.”

Lieserl — Louise hesitated, uncharacteristically.

“I think I know what you’re going to say, Louise.”

Yes. I bet you do, Louise growled. Lieserl, we’re grateful to you for going into New Sol with the wormhole Interface. And you’re sending us a lot of great data. But…

“Yes, Louise?”

Lieserl, you didn’t leave a back-up.

“Ah.” Lieserl smiled and closed her eyes. The neutrino flux from the heart of New Sol brushed against her face, as delicate as a butterfly’s wing. “I wondered how long it would take you to notice that.”

Damn it, Lieserl, that’s the only copy of you in there!

“I know. Isn’t it wonderful?”

You don’t understand. What if something happened to you? Louise went on heavily, Lieserl, we’ve never dropped a wormhole into a VMO before. We’re not sure what will happen.

“No. Well, before my day no one had ever dropped a wormhole into Sol. Nothing much changes, does it?”

Damn it, Lieserl. I’m trying to tell you that you could die.

“Don’t you think I know that? Don’t you see — that’s the whole point?”

Louise didn’t reply.

“Louise, I’m very old. I’ve watched my birth star grow old and die. I’m grateful to you for retrieving me from Sol: I wouldn’t have missed that ride through the Ring for… for half my memory store. But, Louise, I don’t think I can be a human any more — not even a Virtual copy of one. And I don’t want to build worlds… that is for Spi

Lieserl, do you want to die?

“Oh, Louise. I’ve already died once — or so we think, on the neutron star planet with poor Uvarov — and I never even felt it. I don’t want to go through that again.

“This is where I want to be, Louise. Here, inside this new star.” She smiled. “It’s what I was designed for, remember.”

Louise was silent for a while. Then: Come home, Lieserl.

“Louise — dear Louise — I am home.”

Lieserl —

Wistfully, she shut off the voice link to the Northern. She’d open it later, she told herself: when Louise had grown accustomed to the idea that Lieserl was here — here and nowhere else — and here she was going to stay.

And in the meantime, she realized with growing excitement, the processors lodged in the refrigerating wormhole had come to a conclusion about the destiny of her star. New Sol.

She called up a Virtual image of the star; it rotated before her, a crude onion shell.

Already, she knew, oxygen was burning in pockets throughout the star, depositing the more complex elements — carbon, silicon, neon, magnesium — for which the wormhole was designed to trawl. With time, the helium-burning core of the star would contract, leaving a mantle of cooling helium and ash around a center growing ever hotter.

At length — perhaps in half a million years, the processors concurred — oxygen burning would start in earnest in the core…

With growing excitement Lieserl watched the Virtual diorama, ready to learn how she would die.

When oxygen burning started in the core, the star would become immediately unstable.

The mantle would explode. The rotating star would start to collapse, asymmetrically.

Then the core would implode, precipitously.

The giant star’s gravitational binding energy would be converted into a flood of neutrinos, billowing through the collapsing core. Some of the neutrinos would be trapped by the implosion of the core. Others, in the last few milliseconds before the VMO’s final collapse into a black hole, would escape as an immense neutrino pulse…

She remembered the first seconds of her life: her mother’s hands beneath her back, a dazzling light in her eyes. The Sun, Lieserl. The Sun!

In the last moments of her long life, a neutrino fireball would play across the bones of her face.

Lieserl smiled. It would be glorious.

35

Time passed.

After a certain point, even the measurement of time became meaningless. For Michael Poole this moment arrived when there was no nuclear fuel left to burn anywhere, and the last star flickered and died.

Already the Universe was a hundred thousand times its age when the Xeelee left.

Somberly Poole watched the stars evaporate, through collisions, from the subsiding husks of galaxies, or slide into the huge black holes forming at the galactic centers. Then, as the long night of the cosmos deepened, even protons collapsed, and the remaining star-corpses began to crumble.

Poole wearied of puzzling over the huge, slow projects of the photino birds.

He sought out what had once been a neutron star. The carbon-coated sphere, drifting in orbit around a gigantic black hole, was being warmed — at least, kept to a few degrees above absolute zero — by proton decay within its bulk. Poole, as if seeking comfort, clustered his attention foci close to this shadow of baryonic glory.

Maybe there were other baryonic sentients left in the Universe. Maybe there were even other humans, or human derivatives. Poole did not seek them out. With the closure of the Ring, the baryonic story was done.