Nova Sol A

Only southern hemisphere populated: outpost never visible.

Nova Sol B is only visible from the uninhabited northern hemisphere of Capital. Nova Sol B is never visible from the inhabited southern hemisphere of Capital.

Morelles took his pencil again and marked one solar system Alpha and the other Beta. Then he took the scissors and cut along the orbit of the outer planet in each. He was left with two circles of cardboard, each with a sun marked by a dot in the center and the planetary orbits drawn around the sun. He picked up the system marked Beta in his left hand and Alpha in his right. "Now we work in three dimensions instead of two."

Morelles held Alpha perpendicular to the floor and turned the Beta system this way and that. "You can see that I can put the plane of the Beta solar system at any angle to the plane of Alpha's solar system, and this has nothing whatever to do with the plane in which the two stars revolve about each other. Now I'm holding the Beta system at ninety degrees to Alpha, now forty-five, now parallel, now one hundred thirty-five degrees. No matter how I turn it, you can still imagine a circle, a mutual orbit, joining the two suns. They can go around each other no matter what, and don't care about the planes of the planets' orbits."

George nodded enthusiastically. "I see it."

"Good!" Morelles said, beaming. "Now, we have one last step. Let me see. Ah! I see the way." He dropped Alpha and Beta on the top of the round coffee table, then ran back to his office for a pair of thumbtacks. He scooped up the Alpha disk and shoved a pin through its center, through the dot that marked the sun. Then he crouched by the coffee table, and poked the pin through the rim of the table, so the piece of cardboard was perpendicular to the tabletop. The table was a lazy-Susan arrangement, and he spun it around on its pivot until Alpha was on the far side of the table from him. He poked another pin through the Beta system's sun, and shoved that pin into the rim of the table as well. He gave the tabletop another push, and it spun round and round.

Two disks of cardboard, directly across the diameter of the table from each other, held perpendicular to the table-top and parallel to each other, whirled around and around.

As each went past him, Morelles reached out his hand and set the disks spinning around their pushpins.

"There you have it, gentlemen, a first crude armillary, a mechanical representation of Capital's star system. The two stars, which are represented by the push pins, revolve around each other in their mutual orbit, the circumference of which is the rim of my coffee table. The planets orbit around the stars, the pushpins, in the planes of motion represented by the two cardboard disks. The orbital plane of the solar systems are, as Commander Metcalf noted, precessed. They are firmly attached to the rim of my coffee table, and move as it moves. As the two stars revolve through three hundred sixty degrees, a full circle, in their mutual orbit, the orbital planes of the two star systems rotate three hundred sixty degrees."

"Hold it," George said, staring at the model. "If I've got this straight, that means the northern hemisphere of Capital is always pointed at this other star? The other star is always visible from there? And the southern, populated hemisphere is always pointed away from it—which is why we never see it?"

"Right. And the northern lights are like a dawn that never happens—the other sun is just below the horizon, fighting up the sky but never rising," Metcalf put in. He gave the table a spin, and stood up. "Doctor Morelles, I thank you. You might have just solved a big problem."

Metcalf and the astronomer shook hands. "What will you do now?" Morelles asked.

"Start a search through all the catalogs, I guess," Metcalf said. "We'll look for pairs of distant binary stars where one of the stars is the right mass and temperature to support life."

Morelles smiled. "That is my proper work. With all due respect, I am sure I could do a far more sophisticated search than a non-astronomer. Please allow me to do the job. I'd be delighted to do so—and before you say it, I know they'll slap a Top Secret on this at least, and that's fine. I have clearance. I'll get started on it right now."

Movement of Capital around the barycenter of the Nova Sol System. Nova Sol B and Outpost are omitted for clarity.

"Doctor, it's urgent but it isn't that urgent," Metcalf said. "It can wait until morning."

Morelles smiled. "You're forgetting, Commander. Astronomers always work nights."