Supernova Dimming and Angular Distance Diameter

1. Jun 25, 2013

titowakoru

I was reading an article and came across the idea that cosmological measurements of the angular distance diameter could be used to prove that supernova dimming did not occur due to dark energy. However I could not wrap my head around it. Angular distance diameter is giving by:

dA = x / θ where x is the objects actual size and θ is the angular size of the object as viewed from Earth.

When I was reading it, I assumed it had something to do with the redshift relationship but it wasnt particular clear.

Anyone enlightening the situation?

2. Jun 25, 2013

Mordred

without seeing the I couldn't say on the DE relation. The angular size is affected by redshift. beyond redshift approximately z=1.5, the angular diameter distance is a good approximation of proper distance up to that value.

da= r(X)/1+z.

where r(X)=X when k=0 (flat universe geometry).