Hi there everyone, thanks in advance for your thoughts. Those of you coming at this from the thread ‘fighting fire in microgravity’ will know that my current (much, much, stalled) project is a document to help authors who want to write some (just some!) realistic physics into their science fiction. I do this in-person for a few authors already as I've got good qualifications in physics and space technology, and my day job is a physics tutor.
Based on previous feedback I've put up parts of chapter 2 here: The factsheet and a sample of the science section. The full chapter contains more detail on how super nova happen, a ‘what does this mean for a writer’ section that focusses more on descriptions and experiences, and a list of the sources I’ve used. I'm looking for any and all feedback, and if anyone wants to see more of a section, or the sources list, feel free to PM me.
Many thanks again!
1.2: What’s a supernova’s blast radius?
Factsheet:
- Supernova candidates are easy to spot but unpredictable. They come in different types, but by far the most common are:
- The corpse of a star that steals fuel from a living companion, reignites itself, and then becomes unstable and explodes (Type 1a).
- A ‘classic’ big, old, star that becomes unstable due to age and explodes (Type 2).
- Type 2 supernova give off a massive pulse of subatomic particles called neutrinos about 3 hours before they blow. Type 1a are less well understood.
- A supernova fireball is full of rapidly decaying radioactive elements – so it actually keeps getting hotter for weeks after the explosion. It expands at around 10% of lightspeed (30,000 km / sec.
- An Earth like planet would be reduced to a cinder and thrown into interstellar space, even if it were thousands of times further from its star than Earth is from the Sun. Further out…
- At 2 to 5 light years: A bright blue point of light appears in the sky, growing to sun-like brightness over 14 to 30 days. Effects include increased surface temperatures, wildfires, extreme weather, melting of ice caps, lethal radiation levels, total ozone layer loss, and chemical changes to the atmosphere.
- At 20 to 50 light years: The blue light outshines a full moon a thousand times. Radiation levels cause cancers, sterility, birth defects, massive ozone layer loss ( 50% +) , high altitude nitrous oxide smog, increased cloud cover, loss of satellite networks, and lethal radiation dose to astronauts. Other possible effects include an worldwide lightning storms and dementia in humans and animals.
- At 100 to 250 light years: The blue light is comparable to full moon, and radiation causes a measurable spike in cancer and birth defect rates. Other effects include satellite disruption similar to the worst solar storms, increased frequency of lightning strikes, erratic behaviour and memory loss in mammals, and disruption to circadian rhythms.
- A world within 20 light years of the supernova may be engulfed in the expanding cloud of radioactive debris. This will cause more long term effects, including global cooling and an increase in background radiation levels.
The Science:
‘What’s the lethal range of a supernova’ isn’t such a simple question, for a few reasons. The main one is that ‘supernova’ is a term covering a bunch of different kinds of explosions that have one thing in common: Unimaginable size and power….
[the first few paragraphs give a rough run down of how the two most common types of supernova occur, and there’s a list and descriptions of the rarer, exotic, types like hypernova at the end of the chapter]
….that’s what supernova are. But just how far do you need to run to survive?
Thousands of times further away than the Sun from Earth:
This is a good range to start with since, because they are so much bigger and hotter, it’s the kind of distance the habitable zone of a supernova candidate star will be at – although such stars are notoriously badly behaved, so how habitable that would be to humans is debateable. In any case, despite all that extra distance, a planet in the habitable zone would suffer what astrophysicists refer to as ‘massive physical damage’ . In other words: Its surface would be heated until the rock vaporised, then it’s new evaporated rock atmosphere would get stripped away by pummelling by waves of plasma, peeling the planet.
Think a big gobstopper getting the full blast of a flamethrower.
A much shrunken remnant might be left, depending on the specifics of the blast, but for all practical purposes the planet joins Alderaan in the planetary afterlife. Without the gravity of the destroyed central star any remains would drift into interstellar space – so weeks of nuclear fire would be followed by cosmic night and eternal cold.
One to five light years:
With a light year (for reference, one light year is roughly 63000 times the Earth-Sun distance) of range the planet should survive – as in ‘the rocks won't actually melt underfoot’. But even with a two light year gap that’s about as good as the good news gets – the immediate effects of a supernova at that distance are described in the literature as ‘sterilising’: Starting as a purple-blue pinpoint, many times brighter than a full moon, it might take over three weeks to hit its peak, Sun-like, levels of brightness. But the majority of the supernova’s energy isn’t in heat and light but high energy gamma rays, X rays, and high speed sub atomic particles. As the intensity of the blue point grows, the high energy gamma rays would turn the ozone layer into a worldwide smog of nitrous oxide. Truly zero ozone means severe sunburn after 10 minutes of exposure, and if sunburn doesn’t sound so bad, know that we are talking a true ‘clinically severe’ sunburn: Blisters covering large areas, excruciating pain, swelling (especially the face and lips), a blinding headache, dizziness, confusion, disorientation, fever and chills, nausea, vomiting, and dehydration.
Surface radiation levels will rise until standing outside would be the equivalent, radiation dosage wise, of being within a mile of a 10 kiloton nuke - and this would go on for weeks. At its peak standing under the supernova light would mean burns, cancer, sterility, and birth defects. Exactly how much hotter, in the degrees Celsius or Fahrenheit sense, the surface would get depends on exact range and size of the blast – but, given that current climate change fears are based on an overall temperature increase of less than 7 degrees Celsius, imagine the effects of a worldwide 20% temperature increase that lasted for months: Wildfires, and melting of ice caps, massive changes to weather patterns and ocean currents would be the tip of the melting iceberg. Those are major immediate effects*.
This doesn't end with the immediate effects.
Once the supernova has faded there would be a new feature in the sky, above the clouds of smog: Where once there was the brightest, bluest star in the sky would be a nebula - a cloud of superheated plasma and radioisotope bearing dust, expanding at around 10% of light speed. It’d take decades or even centuries to engulf a nearby world, but when it did… Well, an Earth like planet is protected from the natural space radiation by two magnetic fields: Its sun’s, which extends well beyond Pluto in our solar system, and its own smaller but more intense one. As the nebula engulfed a luckless solar system it would collapse the sun’s bubble, exposing a planet in the habitable zone to both the radiation of space and the radiation of the cloud itself. Food chains would collapse as radiation-vulnerable species die off, and the cloud, which is mainly ionised hydrogen and helium, mixes with the upper atmosphere to produce water vapour. The influx of water vapour would build, increasing cloud cover – an effect compounded by interstellar radiation, which has been shown to trigger excessive cloud formation - triggering an ice age. A ‘nebula winter’ as opposed to a nuclear one.
So, at one to five lightyears, your planet survives physically but faces environmental Armageddon - twice.
* There are more, but we’ll meet those properly at longer ranges where they aren’t be swamped by the direct effects.
Twenty to fifty light years:
Here the supernova’s light will be ‘only’ a thousand of times brighter than a full moon, and sheer radiation levels aren’t enough to kill - but their secondary effects can: The planet’s ozone layer will be skinned like a grape in a sandstorm, until being outside during the day would mean severe sunburn within twenty minutes. UV sensitive organisms, especially the ocean algae and plankton that form the base of many food chains, would be devastated, causing a ripple effect of starvation. There would be stranger effects as well, including massive lightning storms: High energy particles…
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