All Questions
8
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Photon speed for an observer at the photon sphere [closed]
I am asked to compute the orbital period of a photon, in the Scwarzschild spacetime, at the photon sphere for an observer at the same radius, $r^\star=3M$. I have computed the result, $\Delta T=6\pi M$...
2
votes
2
answers
238
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Whats the difference between the Photon Sphere and the Marginally bound orbit?
Whats the difference between the Photon Sphere and the Marginally bound orbit?
Why does photon sphere have a radius of 1.5Rs, while the Marginally bound orbit has a radius of 2Rs?
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3
votes
1
answer
639
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Radial motion of a photon in Schwarzschild spacetime
For photon worldlines in the equatorial plane of the Schwarzschild coordinate system ($\theta=\frac{\pi}{2}$) in Schwarzschild space-time, the metric equation is given by,
$$-\Big(1-\frac{2GM}{r}\Big)...
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3
votes
1
answer
182
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Can light of certain wavelengths stably orbit a black hole at the photon sphere?
I've recently learned that for a black hole, its photon sphere is an unstable orbit. Light either manages to escape from or fall into the event horizon, depending on how far away from the edge of the ...
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1
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0
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72
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The event horizon of a black hole supposes an absolute zero in some field?
Based on the Schwarzschild black hole theory, if the gravitational pull of the singularity were to equalize the energy that a photon has by approaching the event horizon from a special angle, would it ...
1
vote
0
answers
90
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Rate of change in de Broglie wavelength in nth orbit.
Suppose I want to calculate the rate of change in de Broglie wavelength of a photon in any orbit number "n" around the black hole. Let it's original de Broglie wavelength be "λ" and the de Broglie ...
- 262
1
vote
2
answers
2k
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An alternative derivation to find the radius of the Photon Sphere of a Black Hole
I know that the radius of the photon sphere of a Black Hole is derived by solving the Einstein field equations and it represents the smallest gravitational stable orbit around the singularity. My ...
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1
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1
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55
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Is it possible for light to fall into a geo-synchronous orbit around a sufficiently massive planet?
Is it possible for (visible) light to fall into a geo-synchronous orbit around a sufficiently massive planet?
Can a planet or heavenly body be massive enough for it to happen?
What will that ...
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