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The Bridge: Discuss an Astronomy Picture of the Day • APOD: Visualization: A Black Hole Disk... (2024 May 08)

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There's far too much here for me to understand, but I'll ask this question: what's the difference between the event horizon and the photons sphere, and why it the photon sphere 50% larger than the event horizon? At least that's what I'm seeing at Wikipedia:

A photon sphere[1] or photon circle[2] is an area or region of space where gravity is so strong that photons are forced to travel in orbits, which is also sometimes called the last photon orbit.[3] The radius of the photon sphere, which is also the lower bound for any stable orbit, is, for a Schwarzschild black hole,

𝑟 = 3 GM/c2 = ³⁄₂ rs

where G is the gravitational constant, M is the mass of the black hole, c is the speed of light in vacuum, and rs is the Schwarzschild radius (the radius of the event horizon); see below for a derivation of this result.

Statistics: Posted by johnnydeep — Wed May 08, 2024 6:07 pm — Replies 8 — Views 266



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