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Venus has a nearly circular orbit. It cannot be a captured planet.
The kinetic energy of a planet (in a single-body system) corresponds to the energy a mass has when falling from a radius of 2a.
If it were from further away, it would have a strong eccentricity.
Assertion:
The accretion disk of a black hole can consist of gas at most.
A massive object would accumulate so much energy when approaching a black hole that it would have to be decelerated significantly to achieve a circular orbit.
Conjecture:
A black hole that isn't currently swallowing a star has no accretion disk at all.
What scientists see as an accretion disk is gas produced by the black hole.
The circular orbit is stabilized by the oncoming flow of particles emerging from the black hole.
Note:
Further from the center, a circular orbit can also be considered achieved,
since less energy is gained during the fall. (e.g., Oort Cloud).
How can something fall into a black hole:
An object with an eccentric orbit is slowed down by tidal friction or gravitational waves.
Light:
Light that isn't incident on the eye or reflected is invisible. Light moves in hyperbolic, circular,
or spiral paths. Circles are likely the exception. Elliptically eccentric or parabolic paths aren't possible.
Light follows the same path both outward and inward (Minkowski metric).
Looking into the center of a black hole has a greater cone of view narrowing
than in neighboring directions. With magnification, it appears darker.
The sides and even parts of the back are seen brighter due to the curvature of the light path.
Light from it pushes into the field of view, even if the straight path is obscured.
Ludwig Resch
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