Planets after a supernova

[Yora]

Despite supernovas being inctedibly energetic, they don't seem to produce a lot of pressure. Binary stars seem to handle the explosion of their companion just fine and I don't think there is much threat to rocky planets either. But of course there would be very noticable effects on the atmosphere's of planets and any life on them.

So let's say we have a planet in the habitable zone of a red supergiant. Given how short lived these things are there probably won't be any native advanced life, but it could have an atmosphere that allows for open-air colonization. What would happen to the planet after the star explodes? This is only for a game, so the most vague generalizations will be sufficient.

First thing: Would the radiation pressure of the blast be strong enough to strip the atmosphere of a planet like Earth?

Second: With the neutron star or black hole that remains having a significantly lower mass than the red supergiant, would any planets on formerly stable orbits fly out into interstellar space? Would this take millions of years spiralling outward or happen within just a few rotations?

And third, would there be any leftover radioactivity on the planet from the innitial exposure to massive radiation? Is such a thing even possible or is irradiation always just a contamination with dust of radioactive elements.
Even if it is the later, supernovas are the origin of all radioactive elements. Would the amount of such elements that bombard the planet be significant?

[HandofShadows]

The atmosphere would be blow away or boiled by the heat. The heat would also vaporize a good chunk of the planet that faced the blast or maybe the whole planet. I really don't think you realize the amount of raw energy produced by a supernova. Big ones put out more energy in a month that the sun does in it's entire existence. :smalleek:

[hamishspence]

There's also kinetic energy - what you've got is a hefty mass of gas hitting your planet, at a speed of 1/10 the speed of light or so. That's going to hit hard.

Based on this article:

https://news.nationalgeographic.com/news/2011/08/110805-planets-survive-supernovas-ejected-rogues-space-science/

planets orbiting at hundreds of AU (so, likely, way beyond the "habitable zone", since the habitable zone of a red giant is on the order of 10 AU - Saturn distance, and a supergiant's wouldn't be vastly further out than that) - would survive but be ejected.

[Yora]

Sorry, changed my post as I realized the initial scenario isn't completely out of the window. I had considered a wide binary system as an alternative, but I think I can stick with the original.

I had not considered the size of the habitable zone. This actually might make the full scenario more plausible. Here is the situation that got me asking:

Villains have the most elaborate plan for a heist:
Step 1: Blow up the star.
Step 2: Wait for the planet to be evacuated.
Step 3: Raid the vaults of the abandoned planet for left behind treasures.
Step 4: Jump out of the system at the very last minute.

This somehow relies on the planet being aware of the star having exploded before the light reaches it, but faster than light detection has always been a thing in science fiction and space opera.

If the star is a red supergiant and the habitable zone is at a distance of 60 AU, this increases the time window for the whole plan from 8 minutes to 8 hours. That could actually work (at least logistically).

At 60 AU the planet would recieve much less radiation than at 1 AU (1 divided by 60² I believe), which probably would lead to a charred but intact planet that has been ejected from a neutron star. And 50 years later the ruins could be visisted.

[hamishspence]

10 light hours is not very wide. Really wide binaries might be as much as a light year apart.

As per the other supernova thread, 30 light years is uncomfortably close.

1 light year would probably be "rip the ozone layer of the planet clean off".

However, the star and planet themselves would survive, and the planet, while radiation-scorched, would probably not have "buildings falling down" from the radiation blast. It's possible that most of the rest of the atmosphere would still be there.

[The_Ditto]

I really like the idea of the planet being completely charred and it's sun dead, but that seems like an unlikely scenario.

Change your way of thinking ..

Star A goes supernova ... wipes out all the planets in it's system / whatever ... doesn't really matter.

Some other Star B .. does "something" ... or something happens there, and Planet "X" is ejected ... happens to arrive at Star A .. and manages to fall into orbit ... :) So viola ... dead planet orbiting dead star .. O.o

:)

[Yora]

I changed my second post as I realized I had not thought of the great distance of the habitable zone around a supergiant.

But my initial backup alternative of a wide binary system might still help. The original scenario I was analyzing actually had about 12 stars being blown up all at once close to each other. If all of them are a wide multiple star system that might not seem as ludicrous as I originally thought.

It still wouldn't look like this:
https://vignette.wikia.nocookie.net/starwars/images/8/81/Cron_system.jpg/revision/latest?cb=20121128165519

[hamishspence]

If the star is a red supergiant and the habitable zone is at a distance of 60 AU, this increases the time window for the whole plan from 8 minutes to 8 hours. That could actually work (at least logistically).

At 60 AU the planet would recieve much less radiation than at 1 AU (1 divided by 60² I believe), which probably would lead to a charred but intact planet that has been ejected from a neutron star. And 50 years later the ruins could be visisted.

It would need to be a bit more than 60AU. The smallest red supergiants that produce Type II supernovae are on the order of 20000x as bright as the Sun, so the habitable zone would be on the order of 140 AU. Given that it'll be infrared-heavy, the planet might need to be a little further out than that.

Lets say 200AU.

[halfeye]

Another factor is that supernovae are not like bombs, they emit for months, so a planet that rotates with respect to the star would be scoured all over, there wouldn't be a side that faced the blast and one that didn't, even Venus would be 60-70% exposed.

[Andor13]

Villains have the most elaborate plan for a heist:
Step 1: Blow up the star.
Step 2: Wait for the planet to be evacuated.
Step 3: Raid the vaults of the abandoned planet for left behind treasures.
Step 4: Jump out of the system at the very last minute.

I'm having trouble conceiving of a group with the power to cause a Star to go Nova off schedule, but which nonetheless considers guardsmen a formidable obstacle.

[Rockphed]

I'm having trouble conceiving of a group with the power to cause a Star to go Nova off schedule, but which nonetheless considers guardsmen a formidable obstacle.

Space Opera, remember. Causing stellar phenomena in order to get around a mundane problem is kinda how they do.

[Yora]

It would need to be a bit more than 60AU. The smallest red supergiants that produce Type II supernovae are on the order of 20000x as bright as the Sun, so the habitable zone would be on the order of 140 AU. Given that it'll be infrared-heavy, the planet might need to be a little further out than that.

Lets say 200AU.
Doesn't really matter, it was magic. But for visiting the ruins decades later, it doesn't make any difference whether the whole think took 8 hours or 24.
But again, thanks for pointing out the much greater distances than in the case of Earth.


Space Opera, remember. Causing stellar phenomena in order to get around a mundane problem is kinda how they do.
It's Star Wars. Stuff like that happens every other week. :smallbiggrin:

[hamishspence]

If the villains can blow up stars - why limit it to stars that will blow up anyway?

If they can make a small star "explode" or at least release a bucketload of energy - as mega-flares - then they can pull their stunt on whatever planetary system they like.

Problem is the evacuation - in Star Wars at least, evacuating planets is hard.

The population of Thanta Zilbra, in the Corellia trilogy, had twelve hours notice to evacuate - and just under a tenth of the 13000 people on the planet escaped.

[Rockphed]

The population of Thanta Zilbra, in the Corellia trilogy, had twelve hours notice to evacuate - and just under a tenth of the 13000 people on the planet escaped.

Is that supposed to have a couple more zeros, or was it really a planet with the population of a very small town?

[hamishspence]

It really did have a small population - more an outpost:

http://starwars.wikia.com/wiki/Thanta_Zilbra_(planet)

the next star that would have been destroyed, if not for Our Heroes, had an estimated population of 12 million:

http://starwars.wikia.com/wiki/Bovo_Yagen_(planet)

and a point is made that if they can't evacuate 10,000 to 15,000 people, evacuating 12 million is even less plausible.

[Strigon]

If the villains can blow up stars - why limit it to stars that will blow up anyway?

If they can make a small star "explode" or at least release a bucketload of energy - as mega-flares - then they can pull their stunt on whatever planetary system they like.

Problem is the evacuation - in Star Wars at least, evacuating planets is hard.

The population of Thanta Zilbra, in the Corellia trilogy, had twelve hours notice to evacuate - and just under a tenth of the 13000 people on the planet escaped.

Idea: come to the planet with a bunch of huge ships; agricultural/water haulers, or whatever you like. Sell your goods, the star blows up, and oh hey; you happen to have the only way offworld for most of the population! How fortuitous!
Charge people exorbitant fees for passage, evacuate, come back later to clean up the scraps. You've got them coming and going!

[Knaight]

It really did have a small population - more an outpost:

http://starwars.wikia.com/wiki/Thanta_Zilbra_(planet)

the next star that would have been destroyed, if not for Our Heroes, had an estimated population of 12 million:

http://starwars.wikia.com/wiki/Bovo_Yagen_(planet)

and a point is made that if they can't evacuate 10,000 to 15,000 people, evacuating 12 million is even less plausible.

That second planet almost certainly has way more ships for the evacuation though - there's a level of built in scaling here.

[Yora]

Ossus was shown to only be the location of the Jedi archives and might not have any other local population. And the Sith actually started their raid while the evacuation was still underway. I think the comic never bothered to mentioned what happened to any non-main characters that were on the planet. (It's a pretty awful comic anyway.)

[Rakaydos]

It's Star Wars. Stuff like that happens every other week. :smallbiggrin:

Isnt that literally the Kyp Durran/Sun Crusher/Cardia plot?

[hamishspence]

Considering a plot point is that the New Republic ships are all tied up in other duty and there's so few to spare that they have to borrow some off Bakura - I suspect that if they wanted to evacuate - they'd have to appeal to the private sector - which would cause panic across the galaxy.

Either way - the point is that

"having the planet's population fully evacuated so that you can plunder freely in the short space of time between the last ship leaving and the shockwave arriving"

is putting too much faith in Evacuation Ability.

[factotum]

Yeah, I agree there--the thing that just seems most unlikely out of all the very unlikely parts of this scenario is the "We'll somehow evacuate the entire population of a planet in between its primary going supernova and the blastwave hitting the planet". Even with a population of only a few million the logistics involved are tremendous, especially since teleportation doiesn't seem to be a thing in the Star Wars universe--so you physically have to get everyone toi walk onto the evacuation transports.

[Yora]

Isnt that literally the Kyp Durran/Sun Crusher/Cardia plot?

No, I think that one was just for the evulz. There was no real point to it other than Dark Side anngst murdering from what I remember. But that series was actually pretty bad.

Blowing up the Cron Cluster was much more planned. The Sith chose the area as a trap for the Republic and Jedi fleet to blow them all up in one go. At the same time a small raiding party would go to the Jedi Library on Ossus and steal the artifacts in the chaos.

Actually, I think both stories were written by the same author around the same time.

[hamishspence]

No, I think that one was just for the evulz. There was no real point to it other than Dark Side anngst murdering from what I remember.

There was a point - of sorts -

Kyp: "Hand over my brother or I'll blow up your star"
Carida: "We'll find out what happened to him"
Carida: "He's dead" (followed by an ambush)
Kyp: "You were stalling me to set up your ambush - I'm blowing up your star to punish you for that. You now have a few minutes, but it will then explode"
Carida: "Actually it turns out he's alive- undo what you've done"
Kyp: "It's not undoable. I'm coming to rescue my brother though"
(Kyp tries, and fails)

[Khedrac]

And this is a classic example of where modern culture, specifically scicene fiction, has corrupted the science so people forget the real meaning of words... (Actually from your other posts I am sure that you would be aware of the error if you stopped to think about it.)

Step 1: Blow up the star.
You have been asking about supernovae (supernovas/supernovii.?) but nothing in this scenario implies that a supernova has to be the result, far more likely is that it woud be a nova and not a supernova. Generally nowadays everyone assumes that an exploding star = supernova which is simply not true.

So, forget having a star that is capable of going supernova and simply go for one that will simply go nova - you willl have far more flexibility in setting up a realistic scenario.

Having found a reference to kilonovae, something I had never heard of, in the Wikipedia article on novae I strongly recommend against them - they require a neutron star and either a second neutron star or a black hole.

[brian 333]

On the particular issue raised by the OP:

When giant stars go nova they destroy everything, even things you wouldn't think about. Ever hear of EMP? When a nuclear bomb goes off it creates a massive spike in the electromagnetic range sufficient to fry electrical and electronic systems. When a star goes off the pulse generated is in every band we've investigated, plus particles like neutrinos and radiation bands we've yet to discover.

Imagine everything within a parsec being tossed into the microwave for a few hours. If it didn't get shredded by stellar ejecta it got melted by radiation.

In other words, there would be nothing but slag when the adventurers came back to rob the place.

Let's go a bit smaller: dwarf stars. Even stars smaller than Jupiter, (diameter, not mass,) pack a huge punch when they go. However, a distant binary might cause the particle/radiation pulse needed to cook the inhabitants while leaving slightly melted pools of gold in the vaults. Red dwarfs tend to be unstable but long-lived while blue ones tend to be very hot until they cool down the spectrum to become red dwarfs. In other words, they are poor candidates for novas.

So, what do we do?

Plasma jets. Every once in a while, quite unexplicably in our current understanding of stellar mechanics, stars eject a fountain of surface material. (It possibly has to do with multi-polar magnetic fields being unstable.) If our intrepid thieves can creatd a plume of stellar material and aim it with some degree of accuracy, we have sufficient energy to evacuate a planet without so much it boils.

[Dervag]

Sorry, changed my post as I realized the initial scenario isn't completely out of the window. I had considered a wide binary system as an alternative, but I think I can stick with the original.

I had not considered the size of the habitable zone. This actually might make the full scenario more plausible. Here is the situation that got me asking:

Villains have the most elaborate plan for a heist:
Step 1: Blow up the star.
Step 2: Wait for the planet to be evacuated.
Step 3: Raid the vaults of the abandoned planet for left behind treasures.
Step 4: Jump out of the system at the very last minute.

This somehow relies on the planet being aware of the star having exploded before the light reaches it, but faster than light detection has always been a thing in science fiction and space opera.

If the star is a red supergiant and the habitable zone is at a distance of 60 AU, this increases the time window for the whole plan from 8 minutes to 8 hours. That could actually work (at least logistically).As noted, what kind of planetary settlement is this, which has great treasures likely to be left behind even though they have so much FTL spacelift capacity that they can pile everyone into ships in a matter of hours and flee the planet entirely?


I'm having trouble conceiving of a group with the power to cause a Star to go Nova off schedule, but which nonetheless considers guardsmen a formidable obstacle.If nothing else, they should be able to transmit from a safe distance a message along the lines of "give us all your loot or we will detonate your sun." And I don't know about you, but I would hand over the loot at that point.

If you're willing to commit grand strategic arson to loot the rubble, you're willing to threaten to commit grand strategic arson to get the locals to hand over the loot voluntarily. Anyone with a big enough army to succeed in plundering the city, has a big enough army to control the city unless it's defended by a force that thinks it can stop the plundering army.

[Lord Torath]

But if you don't want anyone to know you have the loot, then you need to go the evacuation route, and loot after they've evacuated, but before the planet is charred to a cinder, and let everyone assume the loot is similarly charred. But if the loot is that valuable, they'll probably evac it as well, possibly even before all the people are evac'ed. In which case your best bet is to jam their communications, bust in and steal the loot, then make the star go nova and shoot down any ships that manage to evacuate. And have a confederate willing to swear under oath that you were elsewhere at the time.

[Yora]

As noted, what kind of planetary settlement is this, which has great treasures likely to be left behind even though they have so much FTL spacelift capacity that they can pile everyone into ships in a matter of hours and flee the planet entirely?

I believe the planet was home to the central Jedi library and archive and not really much else. Getting most people out is going to go much faster than packing up their entire collection of ancient artifacts. And until the raiding party showed up they didn't even know that they had something that someone wanted to steal.

The whole situation seem more like setting a building on fire than annihilating multiple star systems, but 90s Star Wars comics were weird like that.