High School Gravitational Lensing: Magnification of Galaxies

[Mikael17]

TL;DR

How many time does a galaxy (same size as our milkyway) magnified the background ?

How many time does a galaxy (same size as our milkyway) magnified the background ?

 

[Vanadium 50]

Um...once?

This is impossible to answer. "How strong is a glass lens"?

 

[Ibix]

It doesn't magnify at all, because it's an absolutely terrible lens. It's not even circularly symmetric, so you usually get up to four distorted and displaced copies of whatever is in the background.

 

[Mikael17]

OK, how much would light then bend , when passing nearby a milkyway size galaxy ?

 

[Ibix]

Depends how far away the light is and it depends how massive the galaxy is more than its size. There isn't really a single answer to this question.

Why are you asking? Perhaps if you have a less general question we can be more helpful.

 

[PeroK]

OK, how much would light then bend , when passing nearby a milkyway size galaxy ?

In Hartle's Introduction to General Relativity, he studies the deflection of light for a spherical mass in chapter 9. The estimate is $1.7$ seconds of arc for a light ray grazing the Sun. There would be less deflection for a light ray further from the Sun. In other words, it depends on the mass of the Sun and the impact parameter.

The calculation for the Milky Way would be considerably more complex, as it is not a neat spherical mass. A good project for a computer model, perhaps.