# I Is angular momentum conserved in a Supernova?

1. Jan 4, 2017

### FallenApple

I can see how it would be conserved for the situation of a star turning into a white dwarf since the object is just contracting. Just like the classic ice skater example.

But what about a super nova? Say a star with spin up goes supernova and that the remaining blackhole also has spin up but is rotating much faster.

Does that mean that the remaining fragments will have a total angular momentum vector that is pointing down? Lets assume that not only is the spin rate faster, but the angular momentum vector itself is larger upwards for the blackhole after supernova compared to the upwards vector before as a star. Mathematically, we need an angular momentum vector that is pointing down so that the vector sum is the same as the angular momentum pre-explosion.

Also, conservation makes sense, since there is no external torque form anywhere else in the universe during the implosion/explosion.

But what would this mean? Does it mean that on average, the flying fragments would have spin down?

2. Jan 5, 2017

### Gan_HOPE326

You have to consider that the contraction effect exists on the black hole too. The angular velocity of the black hole might be increased just due to its rotational inertia decreasing (the ice skater effect). Of course the total sum of all momenta still has to be conserved.

3. Jan 6, 2017

### newjerseyrunner

Yeah, you forgot that black holes are puny compared to stars. Stars that go boom are at least 8 times the mass of our sun and the sun is a million km across, a neutron star is maybe a dozen.