What are the forces that give asteroids their shapes? And what shape do neutron stars that do not rotate around its axis have?
Let me try. Corrections welcome.jingles2005 said:What are the forces that give asteroids their shapes? And what shape do neutron stars that do not rotate around its axis have?
Neutron stars are indeed born spinning quickly, but I think the primary cause is conservation of angular momentum. That is, the radius shrinks by orders of magnitude, so small initial spin rates will be magnified:Chronos said:Neutron stars spin to conserve the energy released by the supernova explosion that preceeded them. They typically spin very fast. My argument [and I allow for the possibility I am wrong] is the explosion is assymetric and imparts a huge amount of angular momentum on the fragment.
You're right that it can do both. The torque from the flow of accretion depends on the direction of the orbit. In other words, the infalling matter will hit the neutron star in the same sense as the companion is orbiting around it. If this opposes the spin, then it will be spun down by the torque. One would usually expect them to be spinning and orbiting in the same direction (for the same reason the planets tend to orbit and spin in the same direction), but it's not required. Even if it were spun down, it would eventually be spun up in the other direction as the torque continued.Chronos said:OK, I'll bite, ST. Does not accretion from a binary partner tend to slow down the rotation of a neutron star. I'm thinking tidal forces. Humm, it just occured to me it can also have a spin up effect... astrophysics can be so confusing sometimes...
Actually, I'm saying it wouldn't be. Tidal dissipation would be a trivial effect.Chronos said:Agreed, the accreting mass would be a trivial effect.
As you might suspect, the more massive the asteroid, the more significant gravity becomes in determining its shape. The largest asteroids are roughly spherical. The type of asteroid is also important. Some asteroids are self-gravitating gravel piles whereas others are more solid rock (which would have more odd shapes due to past collisions, etc.).James R said:And about those asteroids...
The shapes of asteroids are fairly random. They are usually too small for gravity to play much of a role. Their shapes are determined by the random way their contents happen to come together, as well as what hits them in their travels.
Doh! I get it now. My denseness sometimes rivals a neutron star.SpaceTiger said:Actually, I'm saying it wouldn't be. Tidal dissipation would be a trivial effect.