Gravitational lensing

[Rex King]

I was trained as an electrical engineer but only used the calculus twice early in my working life and now in retirement could not attempt its use. I seek enlightenment about an accepted scientific fact. It concern gravitational lensing or microlensing. The accepted brightening effect of a star passing behind a black hole screams at me that it cannot be so. I expect to be proven wrong.

 

A standard convex lense has but one focal length so that light converges from lense to focal length and diverges beyond that point. Beyond two focal lengths its brightness is less than it was when reaching the lense.

 

A gravitational lense has a continuous focal length. That is, that at increasing radii the focal length increases. Thus in a point light source ,gravitational lense and observer scenario the dimming and lightening effect should exactly cancel out. One may also consider the fact the lensing effect causes the light to converge circumfrencially but diverge radially. Again these factors should cancel out.

 

That which I envisage would be seen by an observer at any focal length would be the star dimming and growing ‘horns’ as it approached alignment. Faint light passing behind the mass and bending would appear, intensify growing opposing horns and at complete alignment create a halo around the mass. This would continue in reverse order subsequent to alignment.

 

Is there, or has there been, a competent mathematician who can write or has written a computer program which depicts that which would be seen by an observer? I have been unable to find such on the internet.

 

 

 

 

[ajb]

Is there, or has there been, a competent mathematician who can write or has written a computer program which depicts that which would be seen by an observer?

 

The short answer is yes. People have written software programmes to study gravitational lensing. A friend of mine wrote/adapted something for his masters thesis.

 

 

I have been unable to find such on the internet.

 

I don't know what packages or programmes are available to you. Computational astrophysics and astronomy is outside my area of expertise. You could try sending an email to an astronomer at you nearest university. They should have a better idea than I do.