I took some photos on a nice sunny day with my old Pentax K-r. I used fixed aperture mode because I like depth of field in photos. Settings for this particular photo are f/5.6, 1/100s, 55mm and ISO200 according to the exif data.
As you can see in this about 2-3 times zoomed in version of my photo, the yellow surface that is lit up by the sun radiates into the shadowy part behind it.
How is this effect called? How can I prevent it?
Now that's a good explanation - but I'll add one possible tip: if you shoot in RAW format (which may not even be possible on that camera) you may be able to rescue over-exposed areas to some extent in RAW format processing tools. Massively over exposed areas are probably not going to work very well - the colour balance of the rescued image tends to go wrong, for instance - and you may need to use some moderately advanced editing facilities.