But Andros was already speaking quickly, disregarding the Rhodian.

"Commissioner," he said, "the Remorseless has changed position."

"Surely he has not landed on Lingane," said Aratap sharply.

"No," said the major. "He has Jumped quite away from Lingane."

"Ah. Good. He has been joined by another ship, perhaps."

"By many ships, perhaps. We can detect only his, as you are quite aware."

"In any case, we follow again."

"The order has already been given. I would merely like to point out that his Jump has taken him to the edge of the Horsehead Nebula."

"What?"

"No major planetary system exists in the indicated direction. There is only one logical conclusion."

Aratap moistened his lips and left hurriedly for the pilot room, the major with him.

Hinrik remained standing in the middle of the suddenly empty room, looking at the door for a minute or so. Then, with a little shrug of the shoulders, he sat down again. His expression was blank, and for a long while he simply sat.

The navigator said, "The space co-ordinates of the Remorseless have been checked, sir. They are definitely inside the Nebula."

"That doesn't matter," said Aratap. "Follow them anyway."

He turned to Major Andros. "So you see the virtues of waiting. There is a good deal that is obvious now. Wherever else could the conspirators' headquarters be but in the Nebula itself? Where else could we have failed to locate them? A very pretty pattern."

And so the squadron entered the Nebula.

For the twentieth time Aratap glanced automatically at the visiplate. Actually, the glances were useless, since the visiplate remained quite black. There was no star in sight.

Andros said, "That's their third stop without landing. I don't understand it. What is their purpose? What are they after? Each stop of theirs is several days long. Yet they do not land."

"It may take them that long," said Aratap, "to calculate their next Jump. Visibility is nonexistent."

"You think so?"

"No. Their Jumps are too good. Each time they land very near a star. They couldn't do as well by massometer data alone, unless they actually knew the locations of the stars in advance."

"Then why don't they land?"

"I think," said Aratap, "they must be looking for habitable planets. Maybe they themselves do not know the location of the center of conspiracy. Or, at least, not entirely." He smiled. "We need only follow."

The navigator clicked heels. "Sir!"

"Yes?" Aratap looked up.

"The enemy has landed on a planet."

Aratap signaled for Major Andros.

"Andros," said Aratap, as the major entered, "have you been told?"

"Yes. I've ordered a descent and pursuit."

"Wait. You may be again premature, as when you wanted to lunge toward Lingane. I think this ship only ought to go."

"Your reasoning?"

"If we need reinforcements, you will be there, in command of the cruisers. If it is indeed a powerful rebel center, they may think only one ship has stumbled upon them. I will get word to you somehow and you can retire to Tyrann."

"Retire!"

"And return with a full fleet."

Andros considered. "Very well. This is our least useful ship in any case. Too large."

The planet filled the visiplate as they spiraled down.

"The surface seems quite barren, sir," said the navigator.

"Have you determined the exact location of the Remorseless?"

"Yes, sir."

"Then land as closely as you can without being sighted."

They were entering the atmosphere now. The sky as they flashed along the day half of the planet was tinged with a brightening purple. Aratap watched the nearing surface. The long chase was almost over!

Seventeen: And Hares!

To those who have not actually been in space, the investigation of a stellar system and the search for habitable planets may seem rather exciting, at the least, interesting. To the spaceman, it is the most boring of jobs.

Locating a star, which is a huge glowing mass of hydrogen fusing into helium, is almost too easy. It advertises itself. Even in the blackness of the Nebula, it is only a question of distance. Approach within five billion miles, and it will still advertise itself.

But a planet, a relatively small mass of rock, shining only by reflected light, is another matter. One could pass through a stellar system a hundred thousand times at all sorts of odd angles without ever coming close enough to a planet to see it for what it is, barring the oddest of coincidences.

Rather, one adopts a system. A position is taken up in space at a distance from the star being investigated of some ten thousand times the star's diameter. From Galactic statistics it is known that not one time in fifty thousand is a planet located farther from its primary than that. Furthermore, practically never is a habitable planet located farther from its primary than one thousand times its sun's diameter.

This means that from the position in space assumed by the ship, any habitable planet must be located within six degrees of the star. This represents an area only 1/3600th of the entire sky. That area can be handled in detail with relatively few observations.

The movement of the tele-camera can be so adjusted as to counteract the motion of the ship in its orbit. Under those conditions a time exposure will pinpoint the constellations in the star's neighborhood; provided, of course, that the blaze of the sun itself is blocked out, which is easily done. Planets, however, will have perceptible proper motions and therefore show up as tiny streaks on the film.

When no streaks appear, there is always the possibility that the planets are behind their primary. The maneuver is therefore repeated from another position in space and, usually, at a point closer to the star.

It is a very dull procedure indeed, and when it has been repeated three times for three different stars, each time with completely negative results, a certain depression of morale is bound to occur.

Gillbret's morale, for instance, had been suffering for quite a while. Longer and longer intervals took place between the moments when he found something "amusing."

They were readying for the Jump to the fourth star on the Autarch's list, and Biron said, "We hit a star each time, anyway. At least Jonti's figures are correct."

Gillbret said, "Statistics show that one out of three stars has a planetary system."

Biron nodded. It was a well-worn statistic. Every child was taught that in elementary Galactography.

Gillbret went on, "That means that the chances of finding three stars at random without a single planet-without one single planet-is two thirds cubed, which is eight twenty-sevenths, or less than one in three."

"So?"

"And we haven't found any. There must be a mistake."

"You saw the plates yourself. And, besides, what price statistics? For all we know, conditions are different inside a Nebula. Maybe the particle fog prevents planets from forming, or maybe the fog is the result of planets that didn't coalesce."

"You don't mean that?" said Gillbret, stricken.

"You're right. I'm just talking to hear myself. I don't know anything about cosmogony. Why the hell are planets formed, anyway? Never heard of one that wasn't filled with trouble." Biron looked haggard himself. He was still printing and pasting up little stickers on the control panels.

He said, "Anyway, we've got the blasters all worked out, range finders, power control-all that."

It was very difficult not to look at the visiplate. They'd be Jumping again soon, through that ink.

Biron said absently, "You know why they call it the Horsehead Nebula, Gil?"

"The first man to enter it was Horace Hedd. Are you going to tell me that's wrong?"