The Integral Trees

"11mph. Not at this speed. Kendy, I think we should slow down. Decelerate to the minimum at which the Bussard ramjet will work. We won't waste onboard fuel, we'll get a better look, and we can accelerate again when we've got the solar wind for fuel."

"Dangerous," said Kendy. "I recommend against it." And that should have been that.

For five hundred and twelve years Kendy had been editing clumps of experience from his memory wherever he decided they weren't needed. He didn't remember deciding to follow Goldblatt's suggestions. Goldblatt must have persuaded Captain Qui

Kendy remembered:

Levoy's Star and T3 circled a common point in eccentric orbits, at a distance averaging 2.5 x l0^3 kilometers, with an orbital period of 2.77 Earth years. The neutron star had been behind the yellow dwarf while Discipline backed into the system. Now it emerged into view of Discipline's telescope array.

He saw a ring of white cloud, touched with green, with a bright spark at its center. The spectral absorption lines of water and oxygen were coming from there. It was tiny by astronomical standards: the region of greatest density circled the neutron star at 26,000 kilometers-about four times the radius of the Earth.

"Like a Christmas wreath," Claire Dalton breathed. The sociologist's body was that of a pretty, leggy blonde, but her corpsicle memories reached far back…and what was she doing on the bridge? Captain De

The crew of Discipline continued to study the archaic Christmas wreath. Until Sam Goldblatt suddenly crowed, "Goldblatt's World! Prikazyvat Kendy, record that, Goldblatt's World! There's a planet in there."

"I'm not close enough to probe that closely, Sam."

"It has to be there. You know how a gas torus works?"

It was there in Kendy's memory. "Yes. I don't doubt you're right. I can bounce some radar off that storm complex when we pass."

"Pass, hell. We've got to stop and investigate this thing." Goldblatt looked about him for support. "Green means life! Life, and no planet!

We've got to know all about it. Claire, De

Goldblatt's suggestion was not worth considering. Kendy said, "Think. We've got fuel to decelerate once and once only. We'll need it when we reach Earth."

"There's water in there," De

Claire Dalton was gazing at the screen, at a perfect smoke ring with a tiny hot pinpoint in its center. "The neutron star has cooled off, lost most of its rotation and most of its heat and most of that ferocious magnetic field the pulsars have. It's bright, but it's too small to be giving off much real heat. We could probably live in there ourselves." She looked around her. "Isn't this what we came for? The strangeness of the universe. If we don't stop now, we might as well be back on Earth." The contempt in her voice was unmistakable.

Kendy's memory jumped at that point. Hardly surprising. That must have been the true begi

He remembered reviewing and updating his files on gas torus mechanics.

Two planets circled wide around the twin stars: Jupiter-style gas giants with no moons. The old supernova must have blasted away anything smaller.

A body did circle the neutron star. One limb of the Smoke Ring was curdled, a distorted whirlpool of storm. Hidden within was a core of rock and metals at 2.5 Earth masses. There was s6me oxygen and some water vapor in its thick, hot atmosphere. Goldblatt's World was tidally locked, and uninhabitable. Strip away its atmosphere and it might have harbored Earthly life-but its atmosphere was tremendous, dwindling indefinitely into the Smoke Ring itself.

The strong oxygen-water lines were coming from the gas torus.

A gas torus is the result of a light mass in orbit around a heavy mass, as Titan orbits Saturn. It may be that the light mass is too weak to hold its atmosphere. The faster molecules of air escape-but they go into orbit about the heavy mass. Thus, Titan circles Saturn within a ring of escaped Titanian atmosphere, as lo orbits Jupiter within a ring of sulfur ionized by Jupiter's ferocious magnetic field.

A gas torus is thin. The gas must be so rarefied that each molecule can be considered to be in a separate orbit: it must reasonably expect to circle halfway round the primary mass without bumping another molecule. Under such circumstances, a gas torus is stable. The occasional stray photon will bump a molecule into interstellar space; but the molecules are continually reencountering the satellite body.

Titan-smaller than Mars, no larger than Ganymede-carries an atmosphere of refined smog at one and a half times Earth's sea level pressure. The atmosphere is continually being lost, of course, but some of it continually returns from the gas torus.

Levoy's Star was an extreme case, and a slightly different proposition too.

The Smoke Ring was the thickest part of the gas torus around Levoy's Star. At its median it was as dense as Earth's atmosphere a mile above sea level: too dense for stability. It must be continually leaking into the gas torus. But the gas torus was stable: dense, but held within a steep gravitational gradient. Molecules continually returned from the gas torus to the Smoke Ring, and from the Smoke Ring to the storm of atmosphere surrounding Goldblatt's World.

"Goldblatt's World must have started life as a gas giant planet like, say, Saturn. Probably it didn't fall into range until the pulsar had lost a good deal of its heat and spin." Sharon Levoy's crisp voice spoke within Kendy's memory. "Then it was captured by strong Roche tides. It may have dropped close enough to lose water and soil as well as gas. For something like a billion years Goldblatt's World has been leaking gas into the Smoke Ring, and the Smoke Ring has been leaking to interstel lar space. It's not stable, exactly, but hell, planets aren't stable over the long run."

"It won't be stable that much longer," De

Kendy remembered these things. The records had been made while Discipline's instruments probed the Smoke Ring from close range. Already some of the crew were exploring the Smoke Ring via CARMs. Their reports were enthusiastic. There was life, DNA-based, the air was not only breathable, but tasted fine.

Kendy didn't remember bringing Discipline into orbit around Levoy's Star. He must have expended his onboard fuel, postponing by several years his arrival at the target stars along his course. Why?

Claire Dalton's voice: "We've got to get out of this box. It's ru

It was Sharis Davis Kendy who ruled Discipline. Discipline's crew of twenty was hardly necessary to run a seeder ramship. The State had chosen them as a reservoir of humanity: a tiny chunk of the State, far removed from any local disaster. One planet, one solar system, were too fragile to ensure the survival of the State or humankind itself. Every ship in the sky had a crew large enough to begin the human race over again: their secondary mission, if it ever became necessary. The State expected no such disaster, ever but the investment was trivial compared to the reward.