First Light: The Search for the Edge of the Universe

by Preston, Richard

A drumroll of October rain hit the house and reverberated along ponderosa rafters. Gene and Carolyn had lived with their children in the lower house until it had started to feel cramped, whereupon the roof had seemed a natural place to begin another house, especially one made of volcanic boulders. Eventually the children had grown up and moved out, and now Gene’s mother lived in the lower house.

  Gene said, “We are going to go after something new this month.” He picked up a sheet of computer paper and unfolded it. It was titled “Known Trojans,” and it contained a list of heroes from the Trojan War—Achilles, Patroclus, Hektor, Nestor, Priam. Each name was that of a minor planet in orbit around the sun, and each name was followed by a long set of numbers describing that planet’s orbit. A minor planet is the same thing as an asteroid. The whole sheet of Known Trojans consisted mostly of columns of numbers. Lately, Gene said, he had been thinking about these Trojan planets, and he had begun to wonder if there might be a lot of unknown Trojans out there. He ran his finger across blocks of text composed of numbers. “Look at these orbital elements,” he said. “You can just see from these numbers that the Trojan clouds are really enormous.”

  I could not tell anything at all from looking at the computer paper.

  But when Gene Shoemaker looked at those strings of numbers, he could see in his mind’s eye two immense, uncharted clouds of asteroids out by Jupiter. “These clouds,” he said, “cover a heck of a lot of sky. The kind of sky we can explore with a little wide-field telescope.”

  “If the rain stops, Gene.” Carolyn’s voice came out of the kitchen, where she was washing the dishes.

  A lugubrious sound hammered the roof. He looked up. “This is kind of discouraging,” he said.

  Carolyn came out of the kitchen. She said gently, “If it’s raining in Flagstaff, Gene, then it’s raining on Palomar Mountain.”

  What had sparked Gene’s interest in the Trojan asteroids was the simple fact that Carolyn had recently discovered a new Trojan planet while she had been searching through some negatives. She had been looking for earth-approaching asteroids—stray asteroids closing in on the earth—but instead she had found this Trojan out by Jupiter. It was a big planet—a sooty ball about eighty miles across—by far the largest thing the Shoemakers had ever found. After they had photographed it enough to plot its orbit, they were entitled to give it a name. By long-standing tradition this type of planet must be named after a hero from the Trojan war. They studied a copy of The Iliad. In Gene’s words, “The big names were all taken. We thought we were going to have to kind of scrape the barrel, you know. Get into the minor troops.” Then they came across the name Paris. “For some reason, Paris had never been used. I don’t know why. Paris was the guy who started the war.” Paris was one of the sons of Priam, the king of Troy. Paris spent his youth mainly raising sheep. One day he stole Helen from King Menelaos, who was a Greek, and took her to Troy. Menelaos rallied his fellow Greeks to besiege Troy and get Helen back, and that was the beginning of the war between the Trojans and the Greeks.

  There were two clouds of Trojans, one on either side of Jupiter and sharing Jupiter’s orbit. Trojans were faint, slow-moving asteroids, and darker than anthracite coal, which was the reason why only forty Trojan planets had been found, whereas in the Main Asteroid Belt thousands of minor planets had been found. The Shoemakers had realized that the earth was about to make a relatively close approach to one of the two Trojan clouds of asteroids, accompanied by good viewing conditions. They had decided to devote some of their allotted dark time on the eighteen-inch Palomar Schmidt telescope to a search for Trojan asteroids.

  The Trojan clouds had never been completely explored. Scattered pinpoints of light, barely resolvable on the photographic emulsion of a small telescope, Trojan planets were almost impossible to find. They fanned out for half a billion miles on either side of Jupiter. Nobody knew for sure how they had gotten there. Nobody knew for sure what they were made of—except that it was some dark substance.

  In 1906, the German astronomer Max Wolf discovered an asteroid moving in the track of Jupiter’s orbit, wobbling sixty degrees ahead of Jupiter, as if Jupiter were pushing it along. Wolf named the asteroid Achilles. Achilles had somehow wandered into a region of space where the gravitational fields of Jupiter and the sun formed a stable pocket of gravity, leaving the asteroid bobbing up and down in a limbo, unable to escape. In 1772, the French mathematician J. L. Lagrange had predicted such a peculiarity in orbital systems. Lagrange had calculated that there would be dimples in gravity sixty degrees on either side of any body in orbit around another body. A stray object that happened to fall into one of these dimples would oscillate inside the dimple but never leave it again without a push.

  Achilles was the first object found trapped in Jupiter’s leading Lagrangian point. Then an asteroid was found in Jupiter’s trailing Lagrangian point, traveling sixty degrees behind Jupiter, as if Jupiter were pulling it on a track. Soon it became clear that two swarms of minor planets bracket Jupiter, two clouds of black balls dancing on either side of the largest planet in the solar system. A tradition for naming these asteroids after heroes from the Trojan war became established. Asteroids that travel ahead of Jupiter are named for heroes from the Greek side of the war, while asteroids that trail Jupiter are named for heroes from the Trojan side—two seething armies of enemies, ruled by Jupiter. The two clouds are thus known as the Greeks and the Trojans, although astronomers usually refer to both clouds as simply “Trojans.”

  A search for asteroids required photographing points of light that brightened and dimmed like fireflies, as clouds and families of small planets swung around the sun, and the earth overtook and passed them. (The earth moves faster than most minor planets, because it orbits closer to the sun.) Now the earth was about to swing past the Greek cloud of asteroids. During a period of about three months the Greeks—the asteroids that traveled ahead of Jupiter—would slowly pass through the constellation Pisces. They would be visible against a dark, relatively star-free sky, far from the Milky Way, where dense clouds of background stars would otherwise camouflage faint asteroids. This month—October—marked the critical phase, because the core of the Greek cloud was now visible at the top of the sky around midnight. “So are you a crapshooter?” Gene asked me, glancing over his half-glasses. He said, “I think that we are looking at an opportunity to find a heck of a lot more of these guys.”

  The last time anybody had tried to take a census of the Trojan planets was twenty years earlier, when C. J. van Houten, a Dutch astronomer, had searched a few overlapping glass photographic plates that had been taken of parts of the asteroid clouds. He had startled some astronomers when he had declared that there might be as many as nine hundred big undiscovered Trojans out there. Startled or not, no astronomer had gotten around to checking van Houten’s theory.

  Gene Shoemaker offered a more imperial guess as to the number of Trojans. He said, “I think there could be two hundred thousand Trojan planets bigger than a kilometer across, total, for both clouds. We’re talking about a heck of a lot of asteroids—a number roughly the same order of magnitude as the entire Main Belt, I would add that this is not the received wisdom about the Trojan planets.” He suspected that the Trojan clouds might extend far away from the plane of the solar system, where nobody had ever looked systematically for Trojans before. “That’s where we are hoping to hit pay dirt,” he said.

  Asteroid clouds contain a range of debris—everything from dust and sand through boulders to small worlds. If Carolyn, searching films after the run, could discover a handful of big Trojans, that would imply the existence of many small invisible objects. Big Trojans, lurking in parts of the sky where they were not supposed to, would betray a haze of unseen Trojans, swarming like no-see-’ems on either side of Jupiter. Gene said, “These clouds could actually be large shells of material.” Carolyn would scan a pile of negatives, looking not only for Trojans but also for earth-approachers booming past the earth, because one of those guys could tur
n up at any time, on any film. But if the weather failed them, they would have to forget about Trojans for the time being. “This whole thing is a crapshoot, anyway,” Gene said, listening to the rain.

  The next evening, the Shoemakers loaded their Plymouth Fury for the drive to Palomar Mountain. The Fury was a large golden green boat with a smashed front fender. It appeared to have suffered damage during the inexorable march of American science. As large as the Fury was, the Shoemakers had a terrible time fitting their gear into it. Carolyn owned a stereomicroscope that had to go to Palomar Mountain, because she used it to discover comets and asteroids. The microscope took up half the trunk, but the real problem concerned a reporter traveling with the Shoemakers, who carried two backpacks and a duffel bag. Carolyn said, “What have you got in there?”

  “Warm clothes,” I told them.

  “Eeyah,” said Gene skeptically.

  What I did not tell them was that I planned not to be the first reporter to freeze to death during a search for asteroids.

  The Shoemakers preferred to drive to Palomar Mountain at night, because they could push the Fury across the Mojave Desert with less chance of meeting an individual whom Carolyn referred to as “John Law.” Twenty miles outside Flagstaff, the Fury went wahump, and Gene said, “We’re bottoming out on the shocks.”

  “Because you’re driving too fast,” Carolyn said.

  They had wedged me into the backseat, beside my packs.

  She turned around to look out the rear window at a pair of headlights gaining on us. “Is that John Law?” she asked me.

  I turned around to look, and Gene turned around. “Where?” he asked. The Fury swayed and decelerated. A car whipped past us, going at least ninety miles an hour. False alarm—just another Arizonan in a hurry. Putting his foot back on the accelerator, Gene said, apropos of nothing in particular, “Carolyn had a good year last year. She got five comets.”

  She admitted that it was true. She said, “I got so that I expected to find a comet every time we went to the mountain. This year I haven’t found any comets at all. I don’t know what the problem is.” After spending most of her adult life in the profession called housewife, Carolyn Spellmann Shoemaker had become an astronomer. Among other arts, she had learned the art of finding comets. She was a quiet, rather serious person, not given to mentioning her accomplishments, with a strong jawline and a hint of bronze in her skin each fall, which was the last of an outback tan acquired in western Australia. She and Gene spent their summers mapping giant ring structures in the landscape where comets and asteroids had hit the prehistoric earth. Her face gave people the impression that she possessed a secret compass that kept her moving along a private celestial meridian. She would tell people, “I think I was meant to be a hermit,” by which she obviously implied that she was meant to be an old-fashioned astronomer. In the course of searching films for asteroids approaching the earth, Carolyn had begun to turn up comets. Some astronomers considered themselves lucky to find one comet in a lifetime—especially since comets are named for their discoverers. Carolyn had racked up so far a total of six Shoemaker comets, five of which she had discovered during one unbelievable eight-month roll in the year 1984. Before that, no astronomer had ever found five comets in eight months. Two of the Shoemaker comets are what are known as Jupiter family comets: Shoemaker 1 and Shoemaker 2 travel on short orbits around the sun that take them near Jupiter. They will gleam for perhaps ten thousand years before they go dark. Thus the name Shoemaker may last longer than marble or the gilded monuments of princes. The other four Shoemaker comets came through the solar system on long orbits and have now disappeared into deep space.

  Among women, only Caroline Herschel, an Englishwoman who lived in the days of Jane Austen, had found more comets than Carolyn Shoemaker—eight—searching with a modest telescope that her brother, Sir William Herschel, had built for her. “I intend to beat Caroline,” Carolyn remarked coolly. After that she was going to beat Mr. Honda, Mr. Bradfield, and Dr. Mrkos, three astronomers who were then tied for first place among living comet discoverers, with twelve comets each.

  Each observing run on Palomar Mountain yielded a pile of photographic negatives, which Carolyn scanned in Flagstaff using her stereomicroscope. But the microscope went virtually everywhere Carolyn did. She brought it to the mountain in order to search films when Gene brought them fresh from the darkroom, since an earth-approaching asteroid could whip past the earth in a few days. When she searched for comets and asteroids, she inserted pairs of negatives into the microscope—photographs of star fields taken at intervals of forty minutes. An object in motion in the solar system would move enough during forty minutes to appear to jump out before her eyes, in stereo. Each pair of photographs contained around ten thousand stars or starlike objects. Most of them really were stars, yet the photographs were sprinkled with moving debris. Normal asteroids streamed in the same direction, like schooling fish. Abnormal ones, dangerous objects, things that could hit the earth, often went backward, against the normal flow of debris, or they slashed diagonally across the field of view, or they popped out, moving too fast. Carolyn had very sharp eyes, and she was always on the lookout for things that moved.

  “Gene!” she said. “Is that car following us John Law?”

  The Fury rocked as Gene turned around to look. “I hope not,” he said.

  “In Arizona,” Carolyn remarked, “you can be jailed for speeding.” The police had explained this to the Shoemakers before. She did not want a search for minor planets to end in jail.

  The rain stopped and the clouds broke. A whitish pink star gleamed in the west, dead ahead. “Ah, Jupiter,” Carolyn said. “A good sign.” We switchbacked off the edge of the Colorado Plateau and down into the Mojave Desert. Carolyn propped a cassette player on the front seat and played a tape of Herb Alpert and the Tijuana Brass. The Milky Way arched overhead, and Jupiter dropped westward into basin and range. Jupiter is a big planet—the earth would fit easily inside Jupiter’s Great Red Spot. Apart from the sun, Jupiter is the most influential piece of mass in the solar system. It seemed that Jupiter’s gravity was warping Gene’s foot to the gas pedal, pulling the Fury westward. In more than a metaphorical sense, Gene Shoemaker lived with his foot loaded on the accelerator. “I get cranked up over much more than I can finish,” he said. “But I’ve resolved to spend my life, whatever time I have, in doing what’s fun—”

  “Nowadays you have to weed out what’s really fun from what’s just fun,” his wife said.

  “Yeah, I’ve got a bunch of irons in the fire, all interconnected—”

  “If you could only stay off the committees—”

  “Ha!” he said, meaning, “Fat chance.”

  Gene’s scientific work in various fields had earned him some eleven medals and awards, which had piled up whimsically in boxes on top of the piano at home. He had served as a Principal Investigator with various NASA missions to the moon, and now he served as a member of the Voyager imaging team. If the field of impact geology—the study of what happens when a piece of rock or ice hits a planet—could be said to have a founder, it would be Gene Shoemaker. Caltech astronomers, weaned on the Hale Telescope, are quintessentially what are known as extragalactic types. To many of them the solar system is the deadest game in the house, offering little scientific challenge—nine balls of nonluminous matter whirling around a (pathetically) normal star, in addition to some gritty stuff, such as asteroids, moons, and comets: the two-dollar table in the grand casino of the sky. The following comments, which I heard in various places around Caltech at various times, give some idea of the attitude of many astronomers toward the solar system.

  “If it’s inside our galaxy, it isn’t worth looking at.”

  “I simply cannot imagine looking for asteroids as a way to make a living.”

  “Planets are the slag heaps of the universe. The earth is a prime example of that. The only thing the earth is good for is to serve as a platform for a telescope. But we are going to have to
get rid of this atmosphere. Then maybe we will see something interesting.”

  “I could care less if I found a comet. Unless it was going to hit the earth. Then I wouldn’t want my name on it, anyway.”

  Gene Shoemaker offered an oblique reply to defamation of planets. “The solar system is an insignificant bunch of dust,” he admitted. “It also happens to be where we live.” Somewhere in his mind’s eye, or maybe in his heart, Gene carried a peculiar vision of the solar system. It was not any solar system that I had ever heard of before. In schoolbooks the solar system is pictured as a series of flat, concentric circles centered on the sun, each circle representing the orbit of a planet. In Gene’s mind the solar system was a spheroid. In Gene’s mind the solar system was not at all the eternal, unvarying mechanism envisioned by Isaac Newton, but a carnival—a dynamic, evolving cloud of debris, filigreed with bands and shells of shrapnel, full of bits and pieces of material liable to be pumped into ellipses and loops and long, chaotic, wobbling orbits which carried drifting projectiles all over the place—minor planets that, every once in a while, would take a hook into a major planet, causing a major explosion. He said, “There’s just a zoo of beasts out there, roaming the solar system. While it’s tremendous fun discovering these little planets, the real fun is trying to find out what the heck they are and how they fit into the origin of the solar system.” Curiosity, he had decided, was one of the two major forces that drove scientists, the other being a characteristically human wish to make a discovery for which one would be remembered after one was gone. “The trick,” he said, “is to keep the bad ideas to a minimum.” He grinned lopsidedly. “Which is not always possible.” Then he swung the Fury into the breakdown lane and brought it to a halt. Time to switch drivers.

  We piled out of the car onto a ribbon of highway that crossed a desert playa between mountain ranges. Not a pair of headlights was in view. Gene stood in the middle of the road and stretched. He leaned back and looked up. He said, “The Trojans would be dead overhead.” His belt buckle glinted in the starlight—it was made of silver, in the shape of a many-rayed star. The sky glittered with lights, but the cloud of Trojan planets was invisible, twenty thousand times fainter than any star the naked eye could see. “Science,” he suddenly remarked, “is not at all what you think it is.”