Trevize did not like its looks, but he tried not to show it and spoke as matter-of-factly as a guidebook. "There's a big gas giant out there," he said. "It's rather spectacular. It has a thin pair of rings and two sizable satellites that can be made out at the moment."
Bliss said, "Most systems include gas giants, don't they?"
"Yes, but this is a rather large one. Judging from the distance of its satellites, and their periods of revolution, that gas giant is almost two thousand times as massive as a habitable planet would be."
"What's the difference?" said Bliss. "Gas giants are gas giants and it doesn't matter what size they are, does it? They're always present at great distances from the star they circle, and none of them are habitable, thanks to their size and distance. We just have to look closer to the star for a habitable planet."
Trevize hesitated, then decided to place the facts on the table. "The thing is," he said, "that gas giants tend to sweep a volume of planetary space clean. What material they don't absorb into their own structures will coalesce into fairly large bodies that come to make up their satellite system. They prevent other coalescences at even a considerable distance from themselves, so that the larger the gas giant, the more likely it is to be the only sizable planet of a particular star. There'll just be the gas giant and asteroids."
"You mean there is no habitable planet here?"
"The larger the gas giant, the smaller the chance of a habitable planet and that gas giant is so massive it is virtually a dwarf star."
Pelorat said, "May we see it?"
All three now stared at the screen (Fallom was in Bliss's room with the j books).
The view was magnified till the crescent filled the screen. Crossing that crescent a distance above center was a thin dark line, the shadow of the ring system which could itself be seen a small distance beyond the planetary surface as a gleaming curve that stretched into the dark side a short distance before it entered the shadow itself.
Trevize said, "The planet's axis of rotation is inclined about thirty-five degrees to its plane of revolution, and its ring is in the planetary equatorial plane, of course, so that the star's light comes in from below, at this point in its orbit, and casts the ring's shadow well above the equator."
Pelorat watched raptly. "Those are thin rings."
"Rather above average size, actually," said Trevize.
"According to legend, the rings that circle a gas giant in Earth's planetary system are much wider, brighter, and more elaborate than this one. The rings actually dwarf the gas giant by comparison."
"I'm not surprised," said Trevize. "When a story is handed on from person to person for thousands of years, do you suppose it shrinks in the telling?"
Bliss said, "It's beautiful. If you watch the crescent, it seems to writhe and wriggle before your eyes."
"Atmospheric storms," said Trevize. "You can generally see that more clearly if you choose an appropriate wavelength of light. Here, let me try." He placed his hands on the desk and ordered the computer to work its way through the spectrum and stop at the appropriate wavelength.
The mildly lit crescent went into a wilderness of color that shifted so rapidly it almost dazed the eyes that tried to follow. Finally, it settled into a red-orange, and, within the crescent, clear spirals ** drifted, coiling and uncoiling as they moved.
"Unbelievable," muttered Pelorat.
"Delightful," said Bliss.
Quite believable, thought Trevize bitterly, and anything but delightful. Neither Pelorat nor Bliss, lost in the beauty, bothered to think that the planet they admired lowered the chances of solving the mystery Trevize was trying to unravel. But, then, why should they? Both were satisfied that Trevize's decision had been correct, and they accompanied him in his search for certainty without an emotional bond to it. It was useless to blame them for that.
He said, "The dark side seems dark, but if our eyes were sensitive to the range just a little beyond the usual long-wave limit, we would see it as a dull, deep, angry red. The planet is pouring infrared radiation out into space in great quantities because it is massive enough to be almost red-hot. It's more than a gas giant; it's a sub-star."
He waited a little longer and then said, "And now let's put that object out of our mind and look for the habitable planet that may exist."
"Perhaps it does," said Pelorat, smiling. "Don't give up, old fellow."
"I haven't given up," said Trevize, without true conviction. "The formation of planets is too complicated a matter for rules to be hard and fast. We speak only of probabilities. With that monster out in space, the probabilities decrease, but not to zero."
Bliss said, "Why don't you think of it this way? Since the first two sets of co-ordinates each gave you a habitable planet of the Spacers, then this third set, which has already given you an appropriate star, should give you a habitable planet as well. Why speak of probabilities?"
"I certainly hope you're right," said Trevize, who did not feel at all consoled. "Now we will shoot out of the planetary plane and in toward the star."
The computer took care of that almost as soon as he had spoken his intention. He sat back in his pilot's chair and decided, once again, that the one evil of piloting a gravitic ship with a computer so advanced was that one could never-never-pilot any other type of ship again.
Could he ever again bear to do the calculations himself? Could he bear to have to take acceleration into account, and limit it to a reasonable level? In all likelihood, he would forget and pour on the energy till he and everyone on board were smashed against one interior wall or another.