"The thing is," said Trevize, "I've never been this close to a binary system before."
"You haven't?" said Pelorat, open astonishment in his voice. "How is that possible?"
Trevize laughed. "I've been around, Janov, but I'm not the Galactic rover you think I am."
Pelorat said, "I was never in space at all till I met you, Golan, but I always thought that anyone who did manage to get into space-"
"Would go everywhere. I know. That's natural enough. The trouble with planet-bound people is that no matter how much their mind may tell them otherwise, their imaginations just can't take in the true size of the Galaxy. We could travel all our lives and leave most of the Galaxy unpenetrated and untouched. Besides, no one ever goes to binaries."
"Why not?" said Bliss, frowning. "We on Gaia know little astronomy compared to the traveling Isolates of the Galaxy, but I'm under the impression that binaries aren't rare."
"They're not," said Trevize. "There are substantially more binaries than there are single stars. However, the formation of two stars in close association upsets the ordinary processes of planetary formation. Binaries have less planetary material than single stars do. Such planets as do form about them often have relatively unstable orbits and are very rarely of a type that is reasonably habitable.
"Early explorers, I imagine, studied many binaries at close range but, after a while, for settlement purposes, they sought out only singles. And, of course, once you have a densely settled Galaxy, virtually all travel involves trade and communications and is carried on between inhabited worlds circling single stars. In periods of military activity, I suppose bases were sometimes set up on small, otherwise-uninhabited worlds circling one of the stars of a binary that happened to be strategically placed, but as hyperspatial travel came to be perfected, such bases were no longer necessary."
Pelorat said humbly, ".It's amazing how much I don't know."
Trevize merely grinned. "Don't let that impress you, Janov. When I was in the Navy, we listened to an incredible number of lectures on outmoded military tactics that no one ever planned, or intended to use, and were just talked about out of inertia. I was just rattling off a bit of one of them. Consider all you know about mythology, folklore, and archaic languages that I don't know, and that only you and a very few others do know."
Bliss said, "Yes, but those two stars make up a binary system and one of them has an inhabited planet circling it."
"We hope it does, Bliss," said Trevize. "Everything has its exceptions. And with an official question mark in this case, which makes it more puzzling. No, Fallom, those knobs are not toys. Bliss, either keep her in handcuffs, or take her out."
"She won't hurt anything," said Bliss defensively, but pulled the Solarian youngster to herself just the same. "If you're so interested in that habitable planet, why aren't we there already?"
"For one thing," said Trevize, "I'm just human enough to want to see this sight of a binary system at close quarters. Then, too, I'm just human enough to be cautious. As I've already explained, nothing has happened since we left Gaia that would encourage me to be anything but cautious."
Pelorat said, "Which one of those stars is Alpha, Golan?"
"We won't get lost, Janov. The computer knows exactly which one is Alpha, and, for that matter, so do we. It's the hotter and yellower of the two because it's the larger. Now the one on the right has a distinct orange tinge to its light, rather like Aurora's sun, if you recall. Do you notice?"
"Yes, now that you call it to my attention."
"Very well. That's the smaller one. What's the second letter of that ancient language you speak of?"
Pelorat thought a moment, and said, "Beta."
"Then let's call the orange one Beta and the yellow-white one Alpha, and it's Alpha we're heading for right now."
Chapter 17 New Earth
74.
"FOUR PLANETS," muttered Trevize. "All are small, plus a trailing off of asteroids. No gas giants."
Pelorat said, "Do you find that disappointing?"
"Not really. It's expected. Binaries that circle each other at small distances can have no planets circling one of the stars. Planets can circle the center of gravity of both, but it's very unlikely that they would be habitable-too far away.
"On the other hand if the binaries are reasonably separate, there can be planets in stable orbits about each, if they are close enough to one or the other of the stars. These two stars, according to the computer's data bank, have an average separation of 3.5 billion kilometers and even at periastron, when they are closest together, are about 1.7 billion kilometers apart. A planet in an orbit of less than 200 million kilometers from either star would be stably situated, but there can be no planet with a larger orbit. That means no gas giants since they would have to be farther away from a star, but what's the difference? Gas giants aren't habitable, anyway."
"But one of those four planets might be habitable."
"Actually the second planet is the only real possibility. For one thing, it's the only one of them large enough to have an atmosphere."
They approached the second planet rapidly and over a period of two days its image expanded; at first with a majestic and measured swelling. And then, when there was no sign of any ship emerging to intercept them, with increasing and almost frightening speed.
The Far Star was moving swiftly along a temporary orbit a thousand kilometers above the cloud cover, when Trevize said grimly, "I see why the computer's memory banks put a question mark after the notation that it was inhabited. There's no clear sign of radiation; either light in the night-hemisphere, or radio anywhere."