If life had already started to develop on a planet in the habitable zone around HD69830, it would have been unlikely to survive the current LHB event, if this is indeed the correct explanation for the hot dust. On Earth, life may not have started to develop significantly until after our LHB was over, as during the LHB there would have been a number of impacts large enough to cause global environmental catastrophe. In contrast, a planet as old as the HD69830 system can have abundant life. By this age, Earth had considerable single-cell life of different types, possibly including eukaryotes, the ancestors of animals. So in the HD69830 system, we could be observing, at a distance, the destruction of evolution on a life-bearing world. And some systems could go for even longer times before an LHB event. Why not three billion years? Or, for that matter, even 4.6 billion years?
Not that another LHB event is going to happen in our solar system: the orbits of our large planetary bodies are likely to be stable at present and our Kuiper belt has already been depleted. All of this speculation assumes, of course, that the scenario that has been put forward to explain our limited observations of the HD69830 system is the correct one. Many of these conclusions have been derived from simulations that always are based on numerous approximations and assumptions. We will only know what the real explanation is when we have much improved telescopic observations of that stellar system. For instance, in the near future we will have more sensitive infrared observations that will be able to detect dust disks similar in size to that of our own solar system. This will answer the question of whether the disk of our solar system is typical or rare, and thereby tell us a lot about the ways in which planets and planetary building blocks interact during stellar system evolution.
But there are bigger discoveries to be made. It may be that one day we will find a warm, Earth-sized planet in the HD69830 system. Probably it will be called HD69830g or something similar, but this awkward tag hardly seems adequate. Like the other potentially habitable planets that we will find, it really should be named, because, as Carl Sagan once said about the planets of the solar system, the planets of the solar neighborhood are not just dots in the night sky. They are places. They have history, geography and maybe even biology. And they are largely unknown and very far away; but people have always been interested in tales about mysterious, faraway places.
Copyright © 2008 Kevin Walsh
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Acknowledgments: The author would like to thank the administrators of the invaluable star catalog and reference web site Simbad (simbad.u-strasbg.fr/simbad/).
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Further Reading:
Alibert, Y. et al (2006) “Formation and structure of the three Neptune-mass planets system around HD69830.” Astronomy and Astrophysics, 455, L25-L28.
Gomes, R. et al. (2005) “Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets.” Nature, 435, 466-469.
Lovis, C. et al. (2005) “An extrasolar planetary system with three Neptune-mass planets.” Nature, 441, 305-309.
Wyatt, M.C. et al. (2007) “Transience of hot dust around Sun-like stars.” Astrophysical Journal, 658, 569-583.
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About the Author:
Kevin Walsh is an associate professor in the School of Earth Sciences, University of Melbourne. He has interests in climate change, climate variability, and planetary science.
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Novelette: ZHENG HE AND THE DRAGON by Dave Creek
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Illustration by John Alllemand
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You might think first contact would occupy a prominent place in history. But not necesarily...
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Zheng He's exploits numbered so many! I, Ma Huan, served as his translator during his later voyages and, years after, as the chronicler of his travels in the Western Ocean. By the emperor's command, the admiral headed up the treasure fleet, which included as many as sixty-two nine-masted treasure ships, each as large as a sizable village, and nearly two-hundred smaller vessels—supply ships, troop transports, water tankers. His crews amounted to nearly twenty-eight thousand men.
Through Zheng He's accounts and others, I heard of his earlier voyages—tales of silver and silk, tea and wine, oils and candles offered for trade. Of diplomacy that led to the sacred gilin, once thought a myth, becoming a gift for the emperor. Of pirate ships burning and their commanders executed.
I'd heard or witnessed all the stories, or so I believed.
But it seemed Admiral Zheng kept one story untold. It remained the stuff of rumors during his voyages, and I believe in times to come even those rumors will fade.
Once Zheng He captured a dragon.
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Zheng He kept the story of the dragon to himself for many years.
We shared many exploits during his later voyages. I watched as the sultan of Aden bartered pearls, gems, amber, and rose water for our gold, silver, porcelain, and pepper. On a trading and diplomatic mission to Siam, I heard the faint ringing of bells as men strode past, the sound emanating from tiny beads implanted in their scrotums. I stood in witness as Zheng He snubbed the rebel leader Sekanda, so that when he became enraged and attacked us, the admiral possessed a reason to capture him and take him to the emperor for execution.
Finally, he called me to him during his seventh voyage, which would constitute his final one, and said, “I must tell you this most fantastic tale. You may even write it down, though it may never enter your chronicles of my voyages."
Eager to hear any story Zheng He might describe as “most fantastic,” given the many wonders he had experienced, I readily agreed.
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It happened during the first voyage of the treasure fleet, in the fifth year of Emperor Yongle's rule, which the Westerners know as 1407. Zheng He visited the kingdom of Champa to trade porcelains and silks for a rare wood that yielded an expensive and prized incense. His great ships demonstrated the might of Chinese sea power by their mere presence off the countries of Aru and Semudera and Landri, and the Andaman and Nicobar Islands. And in Calicut, which I have referred to in other writings as “the Great Country of the Western Ocean,” he established stable prices for our goods.
Then Admiral Zheng's countless ships set sail for home. He could stand at the square stern of his flagship's observation deck and look back at the wakes of his nearly three hundred vessels and consider himself safe in the knowledge that in springtime, the strong winds and rains of the monsoons traveled to the southwest.
So imagine his astonishment one clear afternoon as he heard a gigantic roll of thunder, long and loud. In the instant before he looked skyward, his anger flared—he and his crew had scrupulously offered prayers and incense to the Celestial Consort, Tianfei, to protect the fleet from such sudden storms.
But as Zheng He gazed past the flagship's red bamboo sails, he saw a dragon half the size of his ship leaving a trail of smoke and descending directly into the center of his fleet.
Years later, Zheng He told me he would never forget the smallest detail of the dragon's approach—it must have ceased breathing flame the instant he looked up, he insisted, because its smoke trailed behind in such a way that it gave the illusion of discharging from the beast's dark blue belly. And he wondered why the dragon's wings, also blue, remained spread wide, without flapping even once. He perceived one more detail—the dragon's snout seemed altogether too blunt. He wondered if the dragon had somehow suffered an injury to its face, because Zheng He looked in vain for evidence of its pointed ears or even of its eyes.
But somehow the dragon realized its course bore down upon one of the fleet's water tankers, because at the last instant it swerved in midair, still without a single flap of wing, before splashing into the wat
ers of the Western Ocean. A great plume of water rose into the air, and the ocean churned as Admiral Zheng ordered the fleet to halt—a complex process involving flags and banners, drums and gongs.
Zheng He's flagship circled the area where the dragon had fallen into the sea. Mists lingered in the air, but try as he might, Zheng He failed to sniff out any odor unique to a dragon.
But Zheng He's vision ranked among the best, and leaning over the bow, he quickly spotted movement beneath the ocean. The dragon rising from the ocean's depths?
No—the dragon's wings spanned at least half the length of Admiral Zheng's flagship. Whatever object or creature rose toward the surface, it had no wings, and its span amounted only to about two zhang—about the same as four tall men lying in a straight line.
As it neared the surface, the object revealed itself as a sphere of the same dark blue shade as the dragon. It propelled itself upward with such force that it popped completely out of the water, only to splash down again and bob on the surface.
Those who served under Zheng He learned then why Emperor Yongle had chosen him for such an important command despite his lack of naval experience. Certainly a eunuch had never received such a large responsibility. The emperor's decision came after counsel he received from a court official who spoke well of Zheng He's rough skin and sparkling eyes, who compared his eyebrows to swords and his forehead to a tiger's.
Now the emperor's wisdom displayed itself for all to see as Admiral Zheng's eyes sparkled anew and his forehead wrinkled with determination. “Break out the nets! Bring that dragon's egg aboard,” he commanded, and as he watched as several of his men gathered giant nets suspended from a wooden frame and tossed it into the ocean. More than one exclaimed his admiration at Zheng He's insight that the sea, having swallowed a dragon, had coughed up one of her eggs. They scooped it up as fishermen would their catch and Zheng He watched as his men strained to lift the egg to the deck.
Within moments, the dripping egg stood on the wooden deck of Zheng He's flagship, its two-zhang height towering over him and his crew. “Excellent,” Zheng He told his men, and strode forward to examine the sphere—for this egg truly manifested itself as such, not the expected oval shape. Zheng He ran his fingers across the smooth surface of the blue egg. He told me these many years later that it did not feel proper, having none of the slightly bumpy texture of a hen's egg, for instance, but rather the utter smoothness of one of his flagship's bronze cannons.
As Admiral Zheng's examination of the egg continued, several of his men eased forward, their own curiosity overriding lingering fear.
But then! The dragon's egg began to rumble, a low sound that insinuated itself through the ship's deck. The crewmen who had drawn close exclaimed in fear and many tripped over each others’ feet in their desperation to escape.
Zheng He, as befitted his position and courage, stepped back in a more leisurely fashion. He stared impassively at the egg as it began to rock back and forth. He could easily imagine the baby dragon inside, frightened or enraged, determined to crack open his shell and strike out against those around him.
"Archers,” Zheng He ordered, and the word passed quickly through the ship and the bowmen arrived within mere heartbeats. They took up position to one side of the egg, bows drawn, awaiting the order to fire should the baby dragon burst forth.
But the egg's rocking motion halted, and its rumblings from within subsided. Even Zheng He later admitted to me what happened next left him without speech for a time.
At first he perceived a vertical line of some sort drawing itself down the side of the egg. Then realization came—not a line, but a seam.
The seam etched itself down nearly half the egg's circumference. Then it created a right angle and traversed the egg horizontally. Another right angle formed, and another, until a square chunk of the egg moved to one side, as if animated on its own. It halted, still somehow attached to the side of the egg.
Then Zheng He caught his first glimpse of the baby dragon, as its blue, lightly scaled hands grasped the edge of the opening. Crewmen raised a great alarm and scrambled across the flagship's deck in confusion. Zheng He concentrated on the dragon's face as it left the shadows of the egg's interior. Its snout appeared much less pronounced than Zheng He expected, and its eyes stared outward through narrow lids. He did not see the pointed ears he expected; indeed saw no evidence of ears at all. Even the light scales of the dragon's upper body faded out as they approached its face. Zheng He hoped to perceive the dragon's personality and intentions with his examination of its features, but he could not just yet.
Admiral Zheng's men quieted as the dragon stared out at them, but when it raised a foot and began to climb out of the egg, they began to shout again. Several of the archers grew noticeably nervous, and a couple of them drew back their bows even more, clearly ready to loose their arrows.
But Zheng He commanded, “Hold!” The archers eased the tension on their bows. For Zheng He noticed what no one else did:
The dragon wore boots.
Zheng He felt that the dragon seemed weak and listless. It proved difficult for the creature to pull itself out of its egg, and the admiral said the prospect of helping the dragon emerge tempted him. But concern for his safety overcame even him, and he stood and watched as the dragon strained to pull itself up and out of the egg. As more the dragon's body became visible, Zheng He saw that it wore a long tunic of some sort that came down past its knees. The light blue garment contrasted with the dragon's dark blue skin. It featured no belt or pockets or any adornments.
But two vertical slits in back allowed the dragon's wings to move freely—or would have, if the dragon could have mustered enough energy to move them. Instead, they fell limply on either side of the dragon's body. They extended from just above its shoulders to just below its waist, but seemed strangely thin. Zheng He wondered how such feeble-looking wings could lift this creature, which, if it ever got to its feet, would stand twice as tall as a man.
A baby dragon would not emerge from its egg fully clothed and dry, Admiral Zheng realized. And the closer he looked at the “egg,” the more it resembled something made, not a natural phenomenon.
Yet the large dragon had clearly tumbled from the sky, releasing this one into the ocean. A mystery, Zheng He thought. Perhaps a dangerous one.
The dragon tumbled onto the deck and landed with a heavy, meaty sound. It raised its head to try to take in its surroundings. Many of Zheng He's men remained frightened even of this weakened creature and told him the archers should fire immediately, that they would find no better moment to destroy the dragon before it took flight and breathed fire and destroyed them all.
"You disappoint me,” he told them. “We serve the Emperor, who sits on the Dragon Throne. We know dragons represent goodness and intelligence.” He pointed at several crewmembers in turn and commanded them, “Take the dragon below. Four of the archers will accompany you.” To one of his commanders, he said, “Summon doctors. Send them down, as well."
Even the most loyal of men might have taken another look at the dragon and hesitated to obey such an order—except from Zheng He. Even so, a couple of men failed to step forward in a lively manner, only to have their superiors beat them bloody, so they would fear them more than the dragon.
It took considerable effort, but eventually the men managed alternately to carry or drag the dragon down into the hold. They cleared a space among the porcelain and gems and the many gifts for barbarian leaders and placed the dragon among them. They tried to place it sitting up at first, then gave up that goal and allowed the dragon to lie upon its left side, careful not to let it crush those thin wings with its own weight.
Admiral Zheng told the men who had brought the dragon that they had served well and could leave. He positioned the archers in shadowed areas around the hold, so they would not unnecessarily frighten the dragon.
At that moment, the doctors arrived, and upon seeing their patient, stopped abruptly, eyes wide, mouths agape. Zheng He told th
em, “You represent my wisest medical men. I give you the challenge of your lifetimes—heal this dragon."
The doctors looked at the limp form of the large creature before them, then at one another, and their silence broke apart into half a dozen overlapping conversations, each doctor proposing a course of action to his colleagues, each contradicting all the others.
Finally Zheng He had heard enough: “Silence!” He pointed at one of the doctors immediately before him, an elderly man with grizzled whiskers, but whose eyes remained keen. “Tell me how you would treat the dragon."
"Typically I would conduct an interview,” the old doctor said. “I would ask the patient about his sleep habits, what he has eaten, whether he has a stressful life. But I can do none of these things with this patient."
Zheng He indicated the doctor standing next to the old man—a younger fellow with an unlined face and a demeanor suggesting an inordinate curiosity. He said, “I would try to find one of the six pulses in the wrist. But the arrangement of this dragon's wrist must surely differ from yours or mine. How can I find such a pulse?"
The third doctor Zheng He bade speak suggested, “I would examine the tongue, if this creature has a tongue. I would check for the red tongue that would tell me of an inflammation. Or the white tongue that would show that the dragon lacks energy. But a dragon—surely to make such an inspection involves risking the dangers of its fiery breath."
Then the dragon began to stir, and it uttered low moans that began deep within its chest and rumbled outward to rattle boxes and barrels next to it in the hold. Even Zheng He felt suddenly aware of the creature's size as it struggled to rise up on its arms. Once it sat upright, it appeared strangely human in its deportment. It sat with its right knee raised and right hand upon that knee. The left leg stretched out before it and the left hand hung to its side.
Analog SFF, January-February 2009 Page 9
