# Ways to make a star go supernova? [closed]

Asking for a fictional storyline.

Say a type iii civilisation on kardashev scale want to make a star go supernova. Then what are the possible ways to achieve this?

The said star being massive enough to go supernova on its own in a few million years.

Would collapsing a Dyson sphere made of iron into the star do it?

What would be the relation between weight of iron and stars mass that would kill it?

• I don't think this is the place for your particulat question, but I just want to point out, if you are thinking about Dyson Spheres, that Dyson himself knew they would be a collection of nodes, connected by articulated sections. A complete sphere is "engineeringly" impossible to build – user171879 Oct 30 '17 at 19:33
• Really this should be asked on Worldbuilding SE. What a type 3 Kardashev civilization could do is way beyond speculation. – StephenG Oct 30 '17 at 19:42
• @StephenG Have Tried Asking Such Questions There But Guess What They Say They Are a fictional content websites so matters relating to real world physics so go to physics SE. lol – user1062760 Oct 30 '17 at 19:45
• @User171879 yeah I'm not calling for a sphere like a ball but say a giant honeycomb structure not entirely continuous. Like an iron grid – user1062760 Oct 30 '17 at 19:49
• Fair enough, it was the symmetry of the infalling complete sphere that I thought you might be considering for a realistic plotline. – user171879 Oct 30 '17 at 19:55

## 2 Answers

One obvious way of making stars go supernova is to drop a black hole inside it. Unfortunately, the accretion rate is surprisingly slow for small black holes. Assuming Bondi accretion, $M'\approx \pi\rho G^2M^2/c_s^3$ where $c_s$ is the local speed of sound. If we assume $c_s\approx 0.1c$ and $\rho\approx 10^{12}$ kg per cubic meter I get $M'(1M_\odot)\approx 1M_\odot$ per second (instant boom), but for a Jupiter mass hole $M'(1M_J)\approx 10^{-6}M_\odot$ per second (about 11 days) and for an Earth mass hole hole about 3,400 years. Same thing for dropping a neutron star or lump of strangelets inside.

This may take a while, especially since there is also an upper limit on the accretion rate due to the Eddington luminosity where the radiation from accretion produces a light pressure that counters the gravity. This limit is around $\dot{M}_{Edd}=4\pi GM/\epsilon c \kappa$ where $0<\epsilon<1$ is the efficiency of converting rest mass into energy ($\approx 0.1$ is standard), and $\kappa$ the opacity ($\approx 3\cdot 10^{-15}$ m$^2$/kg). For a Jupiter mass black hole this is about $8\cdot 10^{-6} M_\odot$ per second so the flow does not choke, but for a solar mass hole this is $9\cdot 10^{-3} M_\odot$ per second - the inflow chokes (this is avoided in "proper" gravitational collapses).

While iron seeding sounds good, you need to add astrophysically significant amounts of iron. I suspect this would be on the order of solar masses, also troublesome.

My best bet would be if one could set up radial oscillations to induce a proper gravitational collapse since the star is by assumption close to the end anyway - maybe a bit of a push is enough. Helioseismology is not my forte, but I can imagine some stars could be pushed over (this at least may happen in white dwarf Type Ia supernovas). You would "just" need to drive the oscillation somehow, perhaps by coupling other modes using your K3 tech.

• Nice answer. I imagine the iron inside a star, once the fusion stops would undergo the equivalent of chandrasekhar collapse, so you probably wouldn't need solar "Masses" of it, a bit over 1 solar mass should be close to enough but it would need a good bit of time to coalesce in the center and condense. How about adding a Neutron star? – userLTK Nov 1 '17 at 8:40

Since it is a fiction. Maybe write a plot where the star is small and was not going to go supernova but still its close towards the end of its life but people are prepared for that timeline, then there is a Dyson sphere that you just collided which increased the mass so much that it is now gonna go supernova really fast and they don't have enough time to do anything about it. To be a red supergiant, the star has to be like 10 times bigger than our sun.

Because it is fiction... let the creativity flow!

• Well it's fiction but its got a story to follow which contains certain events . One of which is where the civilisation blows up the star on purpose to destroy enemies in the star system. As in going from stable to supernova in matter of an hour at most – user1062760 Oct 30 '17 at 19:44
• Stars explode because they run out of fuel. So maybe introduce artificial gravity? A supermassive Dyson sphere or colliding space-ships to increase the star's gravity. That would make the fuel run out faster. Supernova itself takes few seconds and stay in the phase for a long time. The star was gonna go supernova in few thousand years anyway but you just made it run out of fuel in a matter of hours. – LostCause Oct 30 '17 at 19:58
• quora.com/… – LostCause Oct 30 '17 at 20:07
• Stars don't explode because they run out of fuel, they explode because (i) they run out of fuel , collapse very efficiently and then the collapse is abruptly halted or (ii) they ignite all their nuclear fuel in one runaway reaction. – Rob Jeffries Oct 30 '17 at 21:56
• So they don't explode because they run out of fuel but they explode because they run out of fuel in a specific way... we are talking about creating a Dyson sphere (which we have no reason to believe that it is possible) and you are talking about the technicality? This is why people think run away from science (unnecessary details at the wrong time/place). – LostCause Nov 13 '17 at 17:22