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?"

"It may be. They have a different explanation on Earth."

"Oh?"

"They claim it's called that because it looks like a horse's head."

"What's a horse?"

"It's an animal on Earth."

"It's an amusing thought, but the Nebula doesn't look like any animal to me, Biron."

"It depends on the angle you look at it. Now from Nephelos it looks like a man's arm with three fingers, but I looked at it once from the observatory at the University of Earth. It does look a little like a horse's head. Maybe that is how the name started. Maybe there never was any Horace Hedd. Who knows?" Biron felt bored with the matter, already. He was still talking simply to hear himself talk.

There was a pause, a pause that lasted too long, because it gave Gillbret a chance to bring up a subject which Biron did not wish to discuss and could not force himself to stop thinking about.

Gillbret said, "Where's Arta?"

Biron looked at him quickly and said, "Somewhere in the trailer. I don't follow her about."

"The Autarch does. He might as well be living here."

"How lucky for her."

Gillbret's wrinkles became more pronounced and his small features seemed to screw together. "Oh, don't be a fool, Biron. Artemisia is a Hinriad. She can't take what you've been giving her."

Biron said, "Drop it."

"I won't. I've been spoiling to say this. Why are you doing this to her? Because Hinrik might have been responsible for your father's death? Hinrik is my cousin! You haven't changed toward me."

"All right," Biron said. "I haven't changed toward you. I speak to you as I always have. I speak to Artemisia as well."

"As you always have?"

Biron was silent.

Gillbret said, "You're throwing her at the Autarch. "

"It's her choice."

"It isn't. It's your choice. Listen, Biron"-Gillbret grew confidential; he put a hand on Biron's knee-"this isn't a thing I like to interfere with, you understand. It's just that she's the only good thing in the Hinriad family just ROW. Would you be amused if I said I loved her? I have no children of my own."

"I don't question your love."

"Then I advise you for her good. Stop the Autarch, Biron."

"I thought you trusted him, Oil."

"As the Autarch, yes. As an anti-Tyrannian leader, yes. But as a man for a woman, as a man for Artemisia, no."

"Tell her that."

"She wouldn't listen."

"Do you think she would listen if I told her?"

"If you told her properly."

For a moment Biron seemed to hesitate, his tongue dabbing slightly at dry lips. Then he turned away, saying harshly, "I don't want to talk about it."

Gillbret said sadly, "You'll regret this."

Biron said nothing. Why didn't Gillbret leave him alone? It had occurred to him many times that he might regret all this. It wasn't easy. But what could he do? There was no safe way of backing out.

He tried breathing through his mouth to get rid, somehow, of the choking sensation in his chest.

The outlook was different after the next Jump. Biron had set the controls in accordance with the instructions from the Autarch's pilot, and left the manuals to Gillbret. He was going to sleep through this one. And then Gillbret was shaking his shoulder.

"Biron! Biron!"

Biron rolled over in his bunk and out, landing in a crouch, fists balled. "What is it?"

Gillbret stepped back hastily. "Now, take it easy. We've got an F-2 this time."

It sank in. Gillbret drew a deep breath and relaxed. "Don't ever wake me that way, Gillbret. An F-2, you say? I suppose you're referring to the new star."

"I surely am. It looks most amusing, I think."

In a way, it did. Approximately 95 per cent of habitable planets in the Galaxy circled stars of spectral types F or G; diameter from 750 to 1500 thousand miles, surface temperature from five to ten thousand centigrade. Earth's sun was G-0, Rhodia's F-8, Lingane's G-2, as was that of Nephelos. F-2 was a little warm, but not too warm.

The first three stars they had stopped at were of spectral type K, rather small and ruddy. Planets would probably not have been decent even if they had had any.

A good star is a good star! In the first day of photography, five planets were located, the nearest being one hundred and fifty million miles from the primary.

Tedor Rizzett brought the news personally. He visited the Remorseless as frequently as the Autarch, lighting the ship with his heartiness. He was whoofing and panting this time from the hand-over-hand exercises along the metal line.

He said, "I don't know how the Autarch does it. He never seems to mind. Comes from being younger, I guess." He added abruptly, "Five planets!"

Gillbret said, "For this star? You're sure?"

"It's definite. Four of them are J-type, though."

"And the fifth?"

"The fifth may be all right. Oxygen in the atmosphere, anyway."

Gillbret set up a thin sort of yell of triumph, but Biron said, "Four are J-type. Oh well, we only need one."

He realized it was a reasonable distribution. The large majority of sizable planets in the Galaxy possessed hydrogenated atmospheres. After all, stars are mostly hydrogen, and they are the source material of planetary building blocks. J-type planets had atmospheres of methane or ammonia, with molecular hydrogen in addition sometimes, and also considerable helium. Such atmospheres were usually deep and extremely dense. The planets themselves were almost invariably thirty thousand miles in diameter and up, with a mean temperature of rarely more than fifty below zero, centigrade. They were quite uninhabitable.

Back on Earth they used to tell him that these planets were called J-type because the J stood for Jupiter, the planet in Earth's solar system which was the best example of the type. Maybe they were right. Certainly, the other planet classification was the E-type and E did stand for Earth. E-types were usually small, comparatively, and their weaker gravity could not retain hydrogen or the hydrogen-containing gases, particularly since they were usually closer to the sun and warmer. Their atmospheres were thin and contained oxygen and nitrogen usually, with, occasionally, an admixture of chlorine, which would be bad.

"Any chorine?" asked Biron. "How well have they gone over the atmosphere?"

Rizzett shrugged. "We can only judge the upper reaches from out in space. If there were any chlorine, it would concentrate toward ground level. We'll see."

He clapped a hand on Biron's large shoulder. "How about inviting me to a small drink in your room, boy?"

Gillbret looked after them uneasily. With the Autarch courting Artemisia, and his right-hand man becoming a drinking companion of Biron, the Remorseless was becoming more Linganian than not. He wondered if Biron knew what he was doing, then thought of the new planet and let the rest go.

Artemisia was in the pilot room when they penetrated the atmosphere. There was a little smile on her face and she seemed quite contented. Biron looked in her direction occasionally. He had said, "Good day, Artemisia," when she came in (she hardly ever did come in; he had been caught by surprise), but she hadn't answered.

She had merely said, "Uncle Oil," very brightly; then, "Is it true we're landing?"

And Oil had rubbed his hands. "It seems so, my dear. We may be getting out of the ship in a few hours, walking on solid surface. How's that for an amusing thought?"

"I hope it's the right planet. If it isn't, it won't be so amusing."

"There's still another star," said Oil, but his brow furrowed and contracted as he said so.

And then Artemisia turned to Biron and said, coolly, "Did you speak, Mr. Farrill?"

Biron, caught by surprise again, started and said, "No, not really."

"I beg your pardon, then. I thought you had."

She passed by him so closely that the plastic flair of her dress brushed his knee and her perfume momentarily surrounded him. His jaw muscles knotted.

Rizzett was still with them. One of the advantages of the trailer was that they could put up a guest overnight. He said, "They're getting details on the atmosphere now. Lots of oxygen, almost 30 per cent, and nitrogen and inert gases. It's quite normal. No chlorine." Then he paused and said, "Hmm."

Gillbret said, "What's the matter?"

"No carbon dioxide. That's not so good."

"Why not?" demanded Artemisia from her vantage point near the visiplate, where she watched the distant surface of the planet blur past at two thousand miles an hour.

Biron said curtly, "No carbon dioxide-no plant life."

"Oh?" She looked at him, and smiled warmly.

Biron, against his will, smiled back, and somehow, with scarcely a visible change in her countenance, she was smiling through him, past him, obviously unaware of his existence; and he was left there, caught in a foolish smile. He let it fade.

It was just as well he avoided her. Certainly, when he was with her, he couldn't keep it up. When he could actually see her, the anesthetic of his will didn't work. It began hurting.

Gillbret was doleful. They were coasting now. In the thick lower reaches of the atmosphere, the Remorseless, with its aerodynamically undesirable addition of a trailer, was difficult to handle. Biron fought the bucking controls stubbornly.

He said, "Cheer up, Gil!"

He felt not exactly jubilant himself. Radio signals had brought no response as yet, and if this were not the rebellion world, there would be no point in waiting longer. His line of action was set!

Gillbret said, "It doesn't look like the rebellion world. It's rocky and dead, and not much water, either." He turned. "Did they try for carbon dioxide again, Rizzett?"

Rizzett's ruddy face was long. "Yes. Just a trace. About a thousandth of a per cent or so."

Biron said, "You can't tell. They might pick a world like this, just because it would look so hopeless."

"But I saw farms," said Gillbret.

"All right. How much do you suppose we can see of a planet this size by circling it a few times? You know damn well, Oil, that whoever they are, they can't have enough people to fill a whole planet. They may have picked themselves a valley somewhere where the carbon dioxide of the air has been built up, say, by volcanic action, and where there's plenty of nearby water. We could whiz within twenty miles of them and never know it. Naturally, they wouldn't be ready to answer radio calls without considerable investigation."

"You can't build up a concentration of carbon dioxide that easily," muttered Gillbret. But he watched the visiplate intently.

Biron suddenly hoped that it was the wrong world. He decided that he could wait no longer. It would have to be settled, now!

It was a queer feeling.

The artificial lights had been turned off and sunlight was coming in unhindered at the ports. Actually, it was the less efficient method of lighting the ship, but there was a sudden desirable novelty to it. The ports were open, in fact, and a native atmosphere could be breathed.

Rizzett advised against it on the grounds that lack of carbon dioxide would upset the respiratory regulation of the body, but Biron thought it might be bearable for a short time.

Gillbret had come upon them, heads together. They looked up and leaned away from each other.

Gillbret laughed. Then he looked out of the open port, sighed, and said, "Rocks!"

Biron said mildly, "We're going to set up a radio transmitter at the top of the high ground. We'll get more range that way. At any rate, we ought to be able to contact all of this hemisphere. And if it's negative, we can try the other side of the planet."

"Is that what you and Rizzett were discussing?"

"Exactly. The Autarch and I will do the job. It's his suggestion, which is fortunate; since otherwise I would have had to make the same suggestion myself." He looked fleetingly at Rizzett as he spoke. Rizzett was expressionless.

Biron stood up. "I think it would be best if I unzipped my space-suit lining and wore that."

Rizzett was in agreement. It was sunny on this planet; there was little water vapor in the air and no clouds, but it was briskly cold.

The Autarch was at the main lock of the Remorseless. His overcoat was of thin foamite that weighed a fraction of an ounce, yet did a nearly perfect job of insulation. A small carbon-dioxide cylinder was strapped to his chest, adjusted to a slow leak that would maintain a perceptible CO2 vapor tension in his immediate vicinity.

He said, "Would you care to search me, Farrill?" He raised his hands and waited, his lean face quietly amused.

"No," said Biron. "Do you want to check me for weapons?"

"I wouldn't think of it."

The courtesies were as frigid as the weather.

Biron stepped out into the hard sunlight and tugged at the handle of the two-handled suitcase in which the radio equipment was stowed. The Autarch caught the other.

"Not too heavy," said Biron. He turned, and Artemisia was standing just within the ship, silent.

Her dress was a smooth, unfigured white which folded in a smooth drape that fled before the wind. The semitransparent sleeves whipped back against her arms, turning them to silver.

For a moment Biron melted dangerously. He wanted to return quickly; to run, leap into the ship, grasp her so that his fingers would leave bruises on her shoulders, feel his lips meet hers-

But he nodded briefly instead, and her returning smile, the light flutter of her fingers was for the Autarch.

Five minutes later he turned and there was still that glimmer of white at the open door, and then the rise in the ground cut off the view of the ship. The horizon was free of everything but broken and bare rock now.

Biron thought of what lay ahead, and wondered if he would ever see Artemisia again-and if she would care if he never returned.