I Gravitational difference between a black hole and a star

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The discussion explores the differences between black holes and stars in terms of their gravitational effects and how they interact with spacetime. It emphasizes that gravity is primarily determined by mass and rotation, with no influence from other properties like chemistry. The participants debate the implications of black holes being "immaterial" objects, noting that they do not deform or experience friction like material objects do. They also discuss tidal forces and how the gravitational interactions differ between star-star, star-black hole, and black hole-black hole binaries. Ultimately, the conversation highlights the complexities of gravitational dynamics and the unique characteristics of black holes compared to stars.
  • #31
Generally, stars are sufficiently extended that, even when touching, their centers are not close enough, so their orbits are not fast enough, for these waves to carry any significant energy away: When/if they merge, it is because of classical physics, especially friction.

The exception is neutron stars. But even there, a very close pair can take 100 MYr or more for the gravitational waves to carry away enough orbital energy for a merger.
 

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