[Inkscape-user] How to archive an alpha fade out for an image

Hi all,

I'm very new to Inkscape and the possibilities that are made possible with a tools like this, so please forgive me if my question is obvious or otherwise stupid... But I have already searched for an answer to the following on the net and I cannot see how it is done.

I would basically like to archive the same "fade out" on a new image as seen on the attached image. If you put this picture on a dark background, you can see that it kind-of shines.

I have tried with the "Blur Egde" tool (as well as many other approaches, but none of these give me the same illusion.

So... how do you get the same effect? Is it possible at all?