MadSci Network: Astronomy

Re: Are stars really where they are?

Date: Tue Aug 19 12:53:48 2003
Posted By: Kisha Delain, Graduate Student
Area of science: Astronomy
ID: 1060099546.As

Einstein's theory of relativity does mean that light is bent by
gravitational masses.  This is enables us to look for things that we can't
"see" by normal means - we can see their effects on the light coming from
background (further away) objects.  However, for something to significantly
bend light it has to be very very massive.  While you're correct that some
bending will occur, in general for stars it is not enough to be noticable.

You can tell if something is being lensed by the patterns it makes - a
lensed object often appears two or more times around the object its light
is being bent around.  In addition, the images also look "smeared" or
"stretched".  You can see this in the image of the Abell 1689, where
far away galaxies are lensed around a foreground (closer) cluster of galaxies.

Also with regards to stars (in our own galaxy; it's very hard to see
individual stars in other galaxies), to a first approximation if the light
is bent one way, another star will bend it another way - most likely any
(very small) variations would average out by the time the light gets to us.

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