Antares C

[Malenfant]

You know what - sod it, I'll just post the rest of the notes as is. :) I haven't checked the numbers for a very long time, and some of the assumptions we made may be lost in the past.

I think we assumed that the 'snapback' of the 100D limit to the neutron star radius happens when the expanding shell density dropped below 1e-12 kg/m³ (when it reaches about 10800 AU) - until then the 100D is measured from the shell radius.

What follows is the notes I have. Make of them what you will. I'll try to explain things in later posts if people have specific questions. Again, you can put this on the Traveller wiki if the credits are kept.

I've also posted this (and the previously posted System Bible doc) on the SFRPG Discussion forums at http://www.sfrpg-discussion.net/phpB...hp?f=45&t=1922

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Antares Supernova Bible, by Constantine Thomas (c) 2003.

Timings

(T = 0 is core collapse. T - X is before, T + X is after.)

THE BEFORE

T - 1000 years: Carbon begins in core. Neutrino spike emitted.
T - 500 days: Neon burning begins in core. Neutrino spike emitted.
T - 270 days: Oxygen burning begins in core. Neutrino spike emitted.
T - 130,000s: Silicon Burning begins in core. Neutrino spike emitted.


THE BEGINNING

T = 0 : CORE COLLAPSE. Neutrinofront and blastfront starts propagating from core. Internal luminosity climbs to 10 billion Sols (visible when blastfront breaks through stellar surface).
T + 2500s: Neutrinofront passes through stellar surface at 5 AU. Detectable surface ionisation may occur. Blastfront at 0.167 AU (inside star).
T + 75,000s: Blastwave breaks through stellar surface. Lightshell starts propagating at lightspeed from 5 AU. Neutrinofront at 150 AU. Lightshell is always 75,000s behind Neutrinofront.


THE MIDDLE (assuming 100D limit is measured from blastwave shell radius).

T + 150,000s: Blastwave reaches 10 AU. 100D limit reaches Dwarf system. After this, jumps from Dwarf are at -4. Neutrinofront at 300 AU.
T + 270,000s: Neutrinofront reaches Companion Star at 540 AU.
T + 300,000s: Blastwave reaches 20 AU. 50D limit reaches Dwarf system. After this, jumps from Dwarf are at -8. Neutrinofront at 600 AU.
T + 345,000s: Lightfront reaches Companion Star at 540 AU.


THE END (technically there will be a timedelay of up to +/- 6 seconds depending on where planet is relative to Dwarf)

T + 870,000s: Silicon-burning neutrino spike (early warning!) arrives at Dwarf system. (always 130,000s behind core collapse neutrinofront).
T + 1,000,000s: Core Collapse Neutrinofront reaches Dwarf system. Lightfront at 1850 AU, blastwave at 66.7 AU.
T + 1,072,500s: Neutrinofront at 2150 AU. Blastfront at 71.5 AU. Lightfront from front of star travels 1995 AU and reaches Dwarf system. Sub-planet point on Antares surface brightens to 10 billion Sols, grows into a circle of light consuming the surface radiating out from that point as light from rest of the star reaches the planet. Point expands on surface (faster at first, then slower as it spreads to limbs of star). Overall luminosity of Antares increases rapidly.
T + ~1,075,000s: Lightfront from sides of star reach Dwarf system. Entire star reaches 10 billion Sols luminosity, and stays there for about 90,000s. Most of this is in the UV spectrum. Blastwave at 71.67AU.
T + 1,500,000s: Blastwave reaches 100 AU. 10D limit reaches Dwarf system. After this, jump from Dwarf are at -12 (if there’s anyone even left alive there). Neutrinofront at 3,000 AU, Lightfront at 2,850 AU.
T + 2,165,000s: Supernova luminosity as seen from planet has decreased to ~ 1 billion Sols. Visible spectrum luminosity increases as light spectrum shifts from UV to visible light.
T + 8,100,000s: Blastwave reaches Companion Star at 540 AU.
T + 8,776,000s: Supernova luminosity as seen from planet has decreased to ~ 100 million Sols and gradually decreases with time from there.
T + 30,000,000s: Blastfront reaches Dwarf system. Neutrinofront at 60,000 AU (nearly 1 lightyear), Lightfront at 59,850 AU. 5 AU thick Blastfront starts to pass over Dwarf system.
T + ~ 30,075,000s: Rear of blast shell passes through Dwarf system - blastwave effects end, luminosity effects continue.
T + 31,240,000s: Supernova luminosity as seen from planet reaches 10 million Sols. Gradual decrease continues with time.



THE VIEW FROM OUTSIDE (X = Neutrino (lightspeed) travel time between Antares core and observer). This is based on observed and theoretical lightcurves from a 15 solar mass Type II supernova. I’m not sure what makes the luminosity drop though - is this actually happening at the star, or is it because of material in the blastfront changing in opacity as the energy from the supernova drops, or as the shell cools? I’ve assumed that the luminosity changes are happening because of something going on in the central part of the supernova remnant, so the planet sees the luminosity decrease too.

T + X: Neutrinofront reaches observer.
T + X + 75,000s: Supernova lightshell reaches observer.

Also:
T + X + 1,165,000s: Supernova luminosity drops to ~ 1 billion Sols. Visible spectrum luminosity increases as light spectrum shifts from UV to visible light.
T + X + 7,776,000s: Supernova luminosity suddenly drops to ~ 100 million Sols (shell absorption?) and gradually decreases with time from there.
T + X + 30,240,000s: Supernova luminosity reaches 10 million Sols. Gradual decrease continues with time.


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PHYSICAL EFFECTS

I’m going to assume that the luminosity inside the supernova shell decreases as described in ‘View from Outside’.

Companion Star gets extra 46.7 MW/m2 from initial luminosity spike of supernova. Doesn’t really affect it much. When blastwave hits, dynamic pressure is 20 kPa. Effect of blastwave on star uncertain. Possibly not good, but it might hold together.

Dwarf/Planet: Surface Temperature increases to 1970 K due to 10 billion sol luminosity. Effect on Dwarf uncertain - does 1970 K add to the surface temperature? (both are receiving an extra 3.4 MW/m2 from increased luminosity). Dwarf must heat up, since the outside is now hotter than the surface and it can’t cool down. It *can* still hold onto its hydrogen or helium though - so while it puffs out, it doesn’t start losing atmosphere. Not sure what this does to internal pressure - could it cause a runaway expansion as pressure overcomes gravity?

Planet cannot hold onto atmosphere, and it is lost to space very rapidly (heavy gases like SO2 might remain, but they’re very likely to get rapidly photodissociated and lost) - planetary surface melts.

23,400 seconds after luminosity hits ( T + 1098400s), Dwarf has completed one rotation around its axis, exposing all its cloudtops to the increased luminosity. 240,280 seconds after luminosity hits (T + 1315280s), the Planet has completed one orbit around Dwarf and exposed all its surface to the luminosity, so the entire planet is heated.

This heating continues until T + 2,165,000s when luminosity at the Dwarf system drops to 1 billion Sols. Temperature drops to 1100 K, so melting continues. Upper crust of planet is a magma ocean by now. Photodissociation of gases into lighter atoms by luminosity prevents planet from holding onto outgassed volatiles generated by the massive melting. Assuming Dwarf is still around, it can cool off slowly now, but still probably has a rather extended atmosphere.

Cooking continues to T + 8,776,000s, when luminosity has decreased to 100 million Sols. Temperature of Planet drops to 622 K (+maybe a small contribution from the Dwarf), crust might actually be starting to solidify slowly. Luminosity still too high for planet to retain atmosphere. Temperature continues drops slowly over time.

By T + 30,000,000s, the luminosity has dropped to almost 10 million Sols. Planet surface temperature is 350K (solely due to Antares luminosity. The solar constant from Antares is still much higher that the contribution from the Dwarf, which might add a few tens of Kelvin). Surface temperature by this stage is cool enough that it can actually solidify - crust over magma ocean is probably rather thin, only a few tens of metres deep.
However, at this point the blastwave hits the Dwarf and Planet at 10,000 km/s. At this point the shell of material has a density of 2.91e-11 kg/m3 (not much), and hits with a dynamic pressure of 1460 Pa (if you were there, it’d feel roughly as strong as a hurricane wind). However, it impacts the surface as the equivalent of 0.27 megatons of TNT per square metre, which is applied for the next 75,000 seconds. It is probably enough to melt the newly formed crust again and probably thickens the magma ocean, but not enough to do any more significant damage to the planet. Not sure what this does to the Dwarf at all though - some of the distended atmosphere may be blasted away.

So afterwards, it appears that we may still have an intact planet and possibly the dwarf too, and probably the Companion Star (though it sure gets a good dose of metals, which probably will speed up its evolution somewhat...), though the luminosity will remain obscenely high for the next few years. After the blast shell has passed, the planet’s surface can slowly cool off and solidify again - and now it’s enriched with lots of heavy elements, probably including short half-life radioactives like some isotopes of plutonium, uranium and aluminium, and maybe even tiny amounts of the odd superheavy element too. Though that said, there’s still probably a fair bit of debris flying about, and the neutron star in the middle is probably a millisecond pulsar at the very least, so the environment is going to be extremely harsh here for a while.

[Anthony]

Beyond Antares itself, the effects are mostly minor, but it's enough to make a mess of ozone layers and cause radiation problems in a fairly significant area (typical estimates for significant risk seem to be on the order of 8 parsecs).

Hm. Found an old CotI thread about risks to nearby stars, though there's some debate about the threat radius (not sure there's reason to pursue that here, I haven't changed my opinion).

[Hans Rancke-Madsen]

My interest is in the system before the hypothetical supernova event.


Hans

[Malenfant]

Originally Posted by Hans Rancke-Madsen

My interest is in the system before the hypothetical supernova event.

My interest was in the supernova itself, and its consequences (I think Paul was going to cover the pre-supernova stuff, since I'm not really interested in trying to make sense of the OTU as a setting).

[Malenfant]

Originally Posted by Anthony

Beyond Antares itself, the effects are mostly minor, but it's enough to make a mess of ozone layers and cause radiation problems in a fairly significant area (typical estimates for significant risk seem to be on the order of 8 parsecs).

Yeah, it's only really an issue for habitable worlds that can have ozone layers destroyed by the radiation. A colony on a vacuum world would probably just have to hunker down in their solar storm shelters for a bit and then carry on as normal.

[Malenfant]

I think one thing that came up about society post-supernova is that (a) billions were likely to be dead as a result and (b) if billions did get out/were evacuated before the supernova hit then where exactly would they go? The refugees would cause huge disruption to the systems around them (which may also have to evacuate to escape the expanding sphere of radiation), and the Imperium would have an enormous humanitarian disaster on its hands, the likes of which it hasn't seen in one place before.

Also, the (local) interstellar economy would probably collapse completely given that billions of people on Antares are probably going to be more preoccupied about getting the hell out of there before the star explodes (at an unpredictable date) than buying and selling stuff. Ships will be carrying people, not cargo.

[dcarson]

Can you tell those neutrino spikes apart so you know how much warning you are getting? Doesn't help much in a planetary scale, 1000 years is so long that it gets put off, 500 days is too late for anything large scale. However on a individual scale 500 days is plenty of time to flee if you have the resources.

[Malenfant]

Originally Posted by dcarson

Can you tell those neutrino spikes apart so you know how much warning you are getting? Doesn't help much in a planetary scale, 1000 years is so long that it gets put off, 500 days is too late for anything large scale. However on a individual scale 500 days is plenty of time to flee if you have the resources.

Depends if there are other ways to see inside stars. Maybe the neutrinos in the different spikes also have different energy levels?

It also depends on whether anyone was paying attention when the Carbon burning spike happened. Two spikes about 230 days apart might be cause for alarm, or it might just be interpreted as a few weird hiccups in the core. maybe when the third (silicon burning) spike happens people might start to go "er, maybe we should get people out of here...", but they have less than two days before the core collapse then. And of course, people are people, and there'll be debates and naysayers and people claiming that it's much ado about nothing.

And then of course when the core collapse spike hits, it's waaaay too late - and that spike may actually be enough to cause massive radiation damage on its own. While ordinarily neutrinos usually have a very low percentage of interacting with matter, IIRC there are just so many of them passing through (way more than we've ever seen in one go) that there are still a lot of interactions with matter.

[johndallman]

Originally Posted by Malenfant

T + 1,500,000s: Blastwave reaches 100 AU. 10D limit reaches Dwarf system. After this, jump from Dwarf are at -12 (if there’s anyone even left alive there).

Actually, there's a way to survive this in the Dwarf system, if you have a well-supplied ship, strong nerves and act promptly. You use the star as a sunshade - it's much less luminous than the supernova, and big enough to stop a considerable proportions of the neutrinos. You then have to wait until the 100D radius jumps back to the neutron star and then jump out and tell your tale, to general disbelief.

[Anthony]

Originally Posted by johndallman

Actually, there's a way to survive this in the Dwarf system, if you have a well-supplied ship, strong nerves and act promptly. You use the star as a sunshade - it's much less luminous than the supernova, and big enough to stop a considerable proportions of the neutrinos.

It doesn't really stop that many neutrinos, but the dwarf is far enough out that neutrinos aren't that dangerous, the only model where neutrinos were a health threat involved a planet orbiting Antares itself, at around 250 AU.