Why Do We Get an Einstein Cross Instead of a Skewed Ring?

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Einstein crosses occur due to the specific alignment of a background source, lensing mass, and observer, which creates multiple images of the source. This phenomenon is distinct from a skewed ring because the alignment must be nearly perfect for a cross to form, while a skewed ring results from less precise alignment. The discussion references Hartle's book, which provides a detailed explanation of these gravitational lensing effects. Understanding the geometry of light paths in gravitational fields is crucial for grasping why crosses form instead of rings. The topic highlights the complexities of gravitational lensing in astrophysics.
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Why do we ever get Einstein crosses? I realize it is because the alignment is not right, but why do we get a cross because of this instead of just a skewed ring?

Thanks,
Jamie
 
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Unredeemed said:
Why do we ever get Einstein crosses? I realize it is because the alignment is not right, but why do we get a cross because of this instead of just a skewed ring?

Thanks,
Jamie

Hartle's book Gravity: An Introduction to Einstein's General Relativity has a nice treatment of this. I can look it up on Monday.
 
George Jones said:
Hartle's book Gravity: An Introduction to Einstein's General Relativity has a nice treatment of this. I can look it up on Monday.

That would be great, thank you.
 

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