By Bob Berman
A small section of the Bayeux Tapestry depicting Halley’s comet in 1066. Photo by Wikimedia Commons/Myrabella.
After the new-star sighting in April 1006, forty-eight years passed during which nothing momentous occurred. Earthly history was spartan. Nobody was inventing things like printing presses. Few explorers were heading out to sea to find new lands. The sky alone offered noteworthy if disconcerting changes. The most-watched, highest-Nielsen-rating worrisome event happened later in the century, in 1066, when Halley’s comet made an unusually bright appearance. A comet was assumed to signify something disastrous coming — in this case, Halley’s comet accompanied the defeat of the English Saxons in the Battle of Hastings.
But a mere dozen years earlier, a far more cataclysmic event had unfolded in the heavens, and it spooked everyone just as thoroughly as the later comet did. On July 4, 1054, a massive blue star weighing as much as ten of our suns used up the last of its nuclear fuel. Its struggle against its own enormous inward-pulling gravity came to an end. Its core no longer pushed outward with enough nuclear oomph to stop its upper layers from collapsing inward. Stars are gaseous, and gas easily compresses, so once it began, the implosion turned into a runaway.
The smaller a star gets, the greater the gravitational pull at its surface; that makes it still smaller, and on and on it goes. This remains nature’s most astonishing vicious circle. It’s certainly the most violent self-amplifying snowball effect in the cosmos.
Anything that falls converts its gravitational potential energy to energy of some other kind like a falling boulder gaining speed and becoming more destructive. In this case, the conversion created ultra-extreme heat. In less than a minute, the star’s new super-high temperature made an unusual kind of nuclear fusion unfold, quite different from the way our sun shines. The entire massive body of the huge but shrinking blue sun ignited. In mere seconds, the star grew a billion times brighter. It had become a supernova, a type 2, and this particular unfortunate star became astronomers’ all-time-favorite hyper-cataclysm.
Two things happened at once during that single minute a millennium ago. First, most of the top gaseous layers of the unfortunate blue sun exploded outward with the total brightness of a billion suns. This destroyed all the planets orbiting it. Simultaneously, the material that had already fallen inward kept going, accelerated by gravity toward the center, until it formed a ball few physicists really believed could exist until it was discovered in 1967.
But before we examine the astonishing results of this supernova, let’s imagine ourselves back in July of 1054 among the mostly agrarian humans then alive, every one of whom surely stared at the sky in disbelief.
The most impressive scene appeared at the outset, just before dawn on July 5. There, in the wee hours, a thin waning crescent moon rose in the east-northeast in the constellation of Taurus the Bull. But what on earth was next to it?
It looked like a dazzling new star. But it couldn’t be. Though it twinkled madly, which planets rarely do, it was far brighter than any star or planet. The object’s brilliance equaled the moon’s except that all its light was contained in a tiny dot with emanating spikes or rays, the result of the normal astigmatism every eye possesses. It lit up the countryside everywhere. Early risers that morning could see their shadows cast by the dazzling new light. At magnitude −6, it was brighter than Venus at its best. And it was only slightly less intense than the 1006 supernova that had alarmed everyone forty-eight years earlier — and this one was much higher up in the heavens. Such brilliance in a starlike point has never been seen since.
Morning twilight began less than an hour after the new star rose. But the blazing object remained clearly visible in the blue sky even after sunrise. Indeed, it persisted as a daytime star for another three weeks. And though it slowly faded thereafter, it was visible at night for a full year, glued to that spot in Taurus near a medium-bright star astronomers would later name Zeta Tauri, which marks the Bull’s left horn. Well, it’s to our left as we face it. If you were the Bull, it would be your right horn. (After this, we’ll always assume that left means the observer’s left, not the constellation’s.)
If the impossibly bright new star had appeared fifteen hundred years earlier, the inquisitive Greeks would have written about it and speculated about its nature. But in eleventh-century Europe, the reaction was very different. Although most clergymen and some laypeople were literate, not a single writer made mention of this dazzling phenomenon, even though it dominated the night for over a year. The silence was total. And the reason for this is obvious: The sky and its contents belonged to the “heavenly realm” that, according to Church doctrine, was immutable. The unchanging aspect of the cosmos was gospel. Since alterations in the heavens were irreconcilable with the prevailing theology, the strange new object was awkward and unwelcome. The predawn sky was essentially shouting, The Church is wrong! Throughout Europe, not one chronicle mentions a single word about this cosmic faux pas.
Things, however, were different in China and the Middle East. In both places, scribes penned detailed accounts of this guest star, this visitor. As one example, in the Song Shi, the official annals of the Song dynasty, an entry in chapter 12 dated April 6, 1056, says, “The director of the Office of Astronomy reported during the fifth lunar month of the first year of the Zhihe era, a guest star had appeared at dawn, in the direction of the east . . . now it has disappeared.”
Here and there in primitive parts of the world, people created paintings of it.
Of course, acknowledging the star was one thing; people didn’t attempt to explain what they were witnessing. It would have seemed a narrative as coherent as a cat’s dreams. Knowledge of stellar distances lay half a millennium in the future, and even if they had somehow possessed such information, they still would have been flummoxed to learn that this new luminary lay far beyond the supposedly farthest objects, the night’s stars.
A typical naked-eye star lies a few hundred light-years from Earth, though some of our neighbors are ten times closer. The most remote — extraordinary beacons that manage to cast their light across vast distances — hover 3,500 light-years away. But this new star in Taurus sits 6,500 light-years in the distance.
Thus the event’s light had taken that long to get here. This explosion had been en route to Earth since before the Great Pyramids were built.
No one on eleventh-century Earth could even suspect what was happening, but today we can use the hard-won knowledge acquired since then to confidently visualize the unfolding tragedy. It was a schizophrenic tale of huge quantities of brilliant star-material heading opposite ways, each destined to create something so bizarre, they remain monuments to nature’s penchant for inventing seemingly impossible structures.
The bulk of the star furiously exploded outward with a brilliance that would have instantly blinded someone who was observing it from a nearby orbiting planet destined to be burned to a crisp a few minutes later. But the central star-stuff kept getting sucked in the opposite direction — inward. Two suns’ worth of material was packed into an ever-smaller volume. Collapsing like a leaking balloon, this perfect sphere became more condensed until its density equaled that of steel.
But the mushrooming gravity at the surface of the shrinking star was far too great to allow any fragment, any atom of this star’s body, to stop crumpling. The collapse forced its central material, about 600,000 Earth-mass planets’ worth, to continue compacting itself. In just a few seconds, it had shrunk to a ball the size of Earth, and yet it couldn’t stop. Indeed, its collapse was accelerating!
An average star like the sun, though gaseous, has roughly the same density as water. But this Taurus supernova’s material was now packed so tightly that a sugar cube’s volume of it would have outweighed a cement truck.
Smaller and smaller, like Alice. Atoms normally can’t get closer to one another than their electron orbitals, because repulsive electrical forces force them to remain separate. But here, the gravity was so intense, all its atoms were squashed enough to make even twentieth-century assumptions about density limits an illusion. On that day in 1054, nature created something science cannot experimentally duplicate.
The core of the Crab Nebula, the remnant of the supernova. Photo by NASA, ESA, and with acknowledgement to J. Hester and M. Weisskopf.
When the ball of strangeness came to a sudden thudding stop, and an outward-radiating shock wave helped ignite all the star-stuff to set off the titanic explosion we call a type 2 supernova, the star core’s atoms’ solid particles were in contact. Protons had merged with electrons to become neutrons, and all electrical charges vanished. The sphere, only twelve miles wide, was the only part of that star that remained intact and survived the 1054 supernova. Today, we stare at it in disbelief, knowing it’s merely the core of the larger star before it both collapsed and exploded.
Excerpted from Earth-Shattering, Copyright © 2019 by Bob Berman. Used with permission of Little, Brown and Company, New York. All rights reserved.
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