A supernova occurs only once every 100 years in the Milky Way galaxy. And a supernova within our reach is even more unusual.
Since humanity can only visit a small fraction of the galaxy, there is only a 1 in 100 chance that a supernova event is so close that we can fly there.
So, it is quite a coincidence that a supernova occurs just 5,000 light years from the Earth in the Orion arm. That is only a year's flight time. Not close, but feasible.
For a long time, this supernova candidate has been under scientific observation by many species. The star cannot be seen from the Earth because it is hidden behind an interstellar dust cloud. However, it illuminates the cloud and the entire formation is well visible from the Earth. Even before the age of spaceflight it was long suspected that the dust cloud might hide a very bright star.
The star was actually discovered by the GaPax mission, which was able to see the remote side of the interstellar cloud. GaPax stands for Galactic Parallaxes, an expedition that started in 2702 to travel from the Earth to the edge of the Milky Way. The star is a so-called red variable hypergiant of spectral type M4-10epIa. Its changes in luminosity had long been observed as brightness variations of the dust cloud.
Many research organizations have installed their instruments around the red hypergiant. Radiation detectors measure the star across all electromagnetic frequencies. Particle detectors measure the flux of known and hypothetical particles, from neutrinos to gravitons, from relatively slow mass ejections to ultrafast cosmic rays. Neutrinos escaping unhindered from the interior of the star provide a live view into the stellar core. Gravitational waves also show the deformation of space in real-time.
All those sensors feed huge amounts of data into computer models and simulations. A few years before the explosion, the models start moving. The computed probability of a supernova event increases strongly. It grows from the normal background probability of 10e-5 per year to 1 % in 3250 and then to 10 % in 3300. Thus, the supernova explosion does not come as a surprise.
Many astrophysical organizations of the human sphere are waiting for the supernova. Shortly before the event, they update their detectors. They also set up new experiments to confirm exotic theories.
The detectors are located at different distances from the star, depending on what they are supposed to measure. There are "close-in" experiments at less than one hundred astronomical units (AU). At this distance, the instruments are expected to receive 300 million times as much radiation as the Earth receives from the Sun. These are special constructs with shielding of at least 1000 kilometers. In practice, they are cylinders of 1000 kilometer length with alternating sections of field generators, mirrors, cooling elements, conventional radiation-repellent armor, and large engines against the radiation pressure. The scientific instruments are on the far side of the cylinder.
Other sensor networks form spheres at a distance of light-weeks or light-months to measure asymmetric effects accurately. For many research institutes and their staff, this event is the highlight of the century. They invest a huge effort to take this unique chance.
Even though there is a ridiculously large number of instruments from countless organizations, they do not get in each other's way, because space is so big. The only places where experiments pile up are the polar regions. At the poles high-energy experiments are set up because that’s where a gamma ray burst (GRB) is supposed to provide physics experiments with the highest energy density in the universe.
The event actually lasts for months. Although there is a single defined explosion time, the light of the explosion needs weeks and months to reach observers. The main optical wavefront of the explosion is particularly impressive, when the red hypergiant lights up becoming a million times brighter than before. That is a lot of light. The main wave of the radiation is only safe at a distance of several light-years for unprotected observers. At 15 light-years, the supernova shines as bright as the Sun on the Earth. Humans and sophonts of other high-tech civilizations having adaptive optics instead of natural eyes can observe the supernova from as close as two light-years provided they protect themselves from burns.
However, the wavefront takes several years to get that far. Therefore, observers must either wait years, which somewhat spoils the event character, or they travel behind the wavefront with specially shielded ships to close in to the remnants of the star. At a short distance and behind the wavefront they can observe the afterglow, admire the new planetary nebula, and "look at" the newly formed black hole. A planetary nebula must be very impressive from the inside, if you catch the right moment, between different particle and radiation waves. The universe appears brightly lit, animated in real time and in infinite colors across the entire electromagnetic spectrum.
Getting between radiation waves is called wavefront hopping. Modern spaceships can navigate along different wavefronts of the explosion. However, they must be careful to stay in front or behind a particular wavefront. Wavefront hopping is dangerous, because ships are affected by radiation, whether the wavefront itself is moving or the space is pushed through the wavefront by the FTL drive. They can cross wavefronts only in protected regions needing a barrier that can stop the radiation and that is large enough so that ships can hide in its shadow. In this case several large Oort objects and a brown dwarf in the vicinity serve as natural barriers for wavefront hoppers. Just before the wavefront is expected a ship hides behind the barrier waiting for the radiation inferno to pass. Then with the wave ebbing down the ship can leave the shadow and move closer to the star at FTL speed. They just have to make sure that they do not cross a wavefront accidentally and that they get behind a barrier in time to let the next wave pass. Hoppers missing a barrier must stay in front of their current wave for years until it has expanded so far that the radiation level is not lethal anymore.
Many do this on purpose. They enter the supernova behind a barrier and then drift back to safety for months or years in front of a wave, because exiting is even more difficult than entering. To get out of a wavefront, they have to overtake it at FTL speed while staying in the shadow of a barrier. If they deviate only one ten thousandth of a degree from the ideal path, they are lost. Worse, these paths are not linear, because a supernova always has asymmetric and chaotic components. Hoppers can reduce their risk by constantly re-simulating the supernova and providing the simulation with up-to-date data. That is a huge effort. For this purpose, visitor ships, measuring instruments and simulation nodes form gigantic networks payed for by the wavefront hoppers.
Particularly bold observers who want to experience the supernova without having to wait years hide behind shields in the relative proximity of the star. Some fanatics stay only a few light days from the star. They are using shielding cylinders thousands of kilometers long like the "close-in" experiments. Of course, this is not cheap. What they do is not just experiencing the supernova, rather they are surviving it. Later they can boast for centuries about how they survived only light days from a real supernova. Nobody can beat that easily. These adventurers rely on computer models that are accurate but not perfect. If the supernova is only 10 % stronger than predicted, then the safety margins are not sufficient and all the advanced experiments and all of those bold observers vaporize in the electromagnetic wavefront, in the neutrino flood, in the particle inferno or in the expanding stellar shell. In this case they can use their backup, but unfortunately the memory of the event is lost.
For some this fate is intentional. They want to die in the supernova. Sophonts from high-tech civilizations can live very long lives. At the beginning they have an original genetically optimized biological body, then perfect biomechanical spare parts, and finally an android hosting their uploaded consciousness. For some people life becomes boring after such a long time. Can you imagine a better finale for a long life than to merge with the wavefront of a supernova in the certainty that the atoms of your body will form new stars, new planets, and new life?
The supernova is not only a big physics event. The number of visitors is also overwhelming even though only a small fraction of the galactic population attends. Only few civilizations master interstellar distances at this level. Furthermore, while long living sophonts from high-tech civilizations have a different perception of lifetime, only a small part of each population decides to make the long – and usually not quite cheap – journey. Nevertheless, it is estimated that the total number of visitors is in the order of 200 billion beings. Many travel for several years. There are even reports of (and actually interviews with) visitors who travelled twenty Earth years from a region of the Milky Way 30 degrees spinwards. The supernova is truly an event of galactic proportions.
Most visitors are from species that humanity has never heard of before. Even humans are strangers here. The human domain covers about 500 light years and humanity maintains relations as far as 2,000 light years. Fast ships can make 2,000 light-years in four months. Beyond that there are only sporadic contacts. The location of the supernova at a distance of 5,000 light-years is far outside the human sphere of interest. This also applies to most other visitors. They are far away from home. Much further than they usually travel. But the supernova is a very special event for all high-tech civilizations.
The 200 billion visitors are spread over several years in time and space. They arrive with billions of spaceships, a tremendously large number. 30,000 ships arrive just from the human domain alone. But space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is, as the 20th century philosopher Douglas Adams said. Billions of spaceships are lost to cubic light years. The average distance between ships is larger than our solar system. Imagine there are two spaceships on the opposite side of Pluto's orbit and there is nothing in between. In other words: although there are so many visitors you almost never meet them.
Nevertheless, there are places where you can meet other visitors, kind of. Visitor ships are 100 times more frequent in a disk around the equator of the star. The equatorial region seems to be special for most visitors, although the explosion is actually spherically symmetric. Only the poles where the Gamma Ray Burst (the GRB) is expected are really special. The equator is pretty safe from a GRB, though. Maybe that's why people cluster there.
The minimum distance for radiation hardened ships is 40 - 50 light days. This equates to approximately a trillion kilometers. There is a ring around the equator, at the technically possible minimal distance, where shipping traffic is 2000 times higher than in the rest of the sphere. With an average distance of "only" one billion kilometers, visitors almost step on each other's toes.
The traffic becomes dramatic in the shadow of large Oort objects where the wavefront hoppers gather to get behind wavefronts. Although wavefront hoppers make only a few percent of all visitors the absolute numbers are so large, that four million ships meet at each of the 20 Oort objects serving as radiation barriers. All these ships must fit into the shadow of a barrier. Four million spaceships from 10,000 different species crowd together in the barrier's shadow. Getting within 50 kilometers of each other they form a cloud of spaceships, 10,000 kilometers wide and a million kilometers long. A fantastic sight. However, it also makes for difficult maneuvering. The helms of these ships, being sophonts, infomorphs, or unconscious AI do not know each other. They do not know their ways of thinking nor their navigation conventions. They do not even know the types of ships and their capabilities. They also do not have the time to get to know their neighbors. So, there are misunderstandings and accidents happen.
The number of accidents is quite low for such an extreme traffic situation. But the large absolute number still leads to 10,000 crashes with three million fatalities by collisions or when ships are hit by others' exhaust.
Far greater damage is caused by the unexpected fracture of an Oort object. A rather small stray planet with a diameter of 8,000 kilometers at the 130 AU mark is struck by an eccentric micro-GRB caused by one of the countless chaotic eddies in the core of the supernova. It was known that something like this could happen. It was known that gamma ray bursts of lesser intensity occur off the poles in addition to the main GRB at the poles. But nobody had ever expected that one of them would hit an Oort object. The probability of this happening is ridiculously small.
The stray planet consists mainly of water ice. It is more like a giant comet than a planet. When the micro-GRB hits, an ice wedge of 500 kilometers depth evaporates explosively within seconds. The Oort object disintegrates into many fragments drifting apart at 30 kilometers per second. After just one minute, the area that was right in shadow is suddenly illuminated by 11 gigawatts per square meter. That is a hundred times more than the best ships can stand. Although everything is happening so fast, many are able to get to safety behind fragments of the planet. But 200,000 wavefront hopper ships with roughly 60 million beings are too slow. They evaporate and become part of the expanding radiation wave. 50,000 more ships are caught by exhaust ray of their neighbors who – hastily fleeing – navigate less carefully than usual. In total, there are 80 million victims. Most are from high-tech civilizations and almost all have backups, but their memory of the event is genuinely ruined.
Only 60 light years from the supernova there is a Kardashev-1.5 super civilization with ten thousand billion individuals living in several neighboring solar systems. The first humans to make contact are high-energy physicists from a state research institute of the territorial sovereignty of the inner planetary asteroid belt near the gas giant Narhadul in the Ticudeztu system. The physicists have been setting up an experiment that will use the north pole GRB, when some components fail that cannot be manufactured locally. While searching for replacements they meet engineers from the super-civilization 60 light years away preparing their own experiment. They call them the Taumass.
The name Taumass is derived from the term "Tau mass" because these alien scientists are conducting an experiment that is supposed to determine the mass of the Tau elementary particle to a very high precision. They are also using the north pole GRB, because even though their civilization is much more advanced, they cannot produce such a high energy density in a laboratory, either.
Both teams describe their own experiment and that of the others in their languages. This is sufficient as a common basis to get automatic translators up and running quickly. The description of their experiments is the first complex information that the two teams exchange. This shapes the human scientists' perception of the strangers. And since the humans talk among themselves about the "tau mass guys", the term "Taumass" sticks as a name for the entire species.
In any case, the Taumass can actually help. The defective components are replaced by the Taumass' fabs on the spot. As payment, the humans hand over their entire database of entertainment programs, because humanity's material assets or technical know-how is not of any value to the Taumass, their tech level being quite a bit higher.
Many other supernova visitors also visit the Taumass. The Taumass cluster is very impressive even for members of high-tech civilizations. Since most visitors spend months or years in the vicinity of the supernova, there is enough time to explore the region. Many hear about the Taumass and visit their cluster. It is estimated that a total of 50 billion supernova visitors in 300 million ships take the Taumass cluster as a tourist attraction.
While visiting the Taumass cluster, some humans run into Mansalu individuals which happen to be there in physical form or as infosophonts. A statistical extrapolation amounts to 300 billion Mansalu individuals, in addition to the estimated 200 billion visitors of other species who arrive in spaceships like the humans. Rumors have it, that the Mansalu come via a hyperchannel that connects the Mansalu complex with the Taumass cluster at high FTL speed. But there is no independent confirmation.
The Taumass have the capacity for so many visitors. They know what is in store for them. And they are prepared. They not only take care of all those visitors, but they also care for their interstellar neighborhood.
Only six light years from the supernova, the Stone Age population of an entire planet is doomed. So, aid organizations of the Taumass move all 80 million beings and their biosphere into well shielded artificial habitats.
At a distance of 10 light years the existence of a planet-bound technical civilization with 20 billion people is threatened. At this distance there is no need to evacuate. Shielding helps against radiation while decontamination can neutralize the radioactive fallout. But the effort is huge, and the local civilization cannot cope at its tech level. Therefore, the Taumass help to protect the planet. With their high-tech means they build a shield for the whole planet. They also provide the local civilization with facilities to decontaminate the biosphere, with fabs for the production of radiation shields and many other technologies that enable the local population to help themselves. Preparations are still underway when the supernova explodes. At that point there is still 10 years time until the first wave arrives.
Then a second sun illuminates the celestial bodies of the system. Only the home planet is completely protected. For the other planets the supernova is brighter than their own sun. The outer planets receive a thousand times more energy than before. This causes dramatic changes, but the local civilization can cope with that. After a few weeks, the supernova fades back. On the other planets of the system, effects of the energy flood remain for decades.
Then waves of radioactive particle showers begin. First to arrive are almost lightspeed fast protons and electrons. Only a few percent penetrate the planetary shielding reaching the atmosphere. Charged particles spiral down along magnetic field lines and for some years there are fantastic auroras, even down to the equator.
Next are heavier elements, starting with alpha particles, then fast carbon nuclei, with a high proportion of radioactive C14, which is bad, finally calcium ions and iron cores. Large locally built plants and Taumass nanotechnology are working feverishly to filter radioactive isotopes from the biosphere. An artificial dust cloud cools the planet compensating the energy input from supernova particles that heat up the atmosphere. A veil of smog covers the planet and makes wonderfully colored sunsets. Ten years later highly enriched nuclei of heavy elements arrive – and nothing is beautiful anymore.
Taumass forces block off all solar systems with indigenous populations within 300 light years. Thus, they prevent millions of spaceships in search of further sights from disturbing the local, often non-space-flying peoples.
The Taumass also organize sightseeing tours through their own cluster allowing visitors to admire the huge structures of Taumass Prime. Visitors learn about the cluster-wide real-time information network. With their own shuttles they can even use the FTL converter tracks to travel almost instantaneously between Taumass population centers in different solar systems.
There are also guided tours to interesting sights of the interstellar region. For example participants can observe the evacuation of a Stone Age population from Roanoke IV including their biosphere or the construction of a full scale planetary shield for Nuirus B. In total the Taumass guide 200 million visitor ships in a controlled way through the interstellar neighborhood. Thanks to all these measures only few regional civilizations are disturbed in their development.
Even the resettled natives of Roanoke IV only vaguely remember later the "time of great changes". Their descendants only know the world as it is and when their elders tell at the campfire that there used to be no sky band behind the horizon, the youth just wonder a little bit, because everyone knows that the sky band holds the world together.
The ejected shell of the former hypergiant expands at a rate of a few thousand kilometers per second. It will soon form a planetary nebula. 30,000 years later, the shock wave will compress the gas cloud that was always visible from the Sol system. This will trigger the formation of new stars with their own new planetary systems and maybe new life, as it has always been.
What humans do not know – and probably no one below the level of super-civilizations like Taumass and Mansalu – the atoms of 3,000 billion Mansalu are being blown away by the new planetary nebula: a perfect opportunity for them to become one with the universe, and so easily accessible via Inter-Cluster-Expressway.
Most visitors leave the region of the supernova after months or years. They return home taking with them the memory of a truly galactic event, the supernova, the Taumass cluster, 10,000 species, and millions of ships.
It gets quiet around the former red hypergiant. Only the black hole remains and a quadrillion abandoned instruments.