How did you make these stars? I experienced quite some ugly AA due some filters and wasn´t able to get rid of them: “Exterior glow” for example “smoothes” out the original image some times some times not.
Have you tried to convert you graphic via “Object->Convert->To Image” already? See if this helps.
The artwork was saved as a JPEG and a PNG. The files were opened in separate Safari windows and a screengrab taken. This was opened in Preview. As you can see, there’s virtually no difference between the JPEG and PNG versions.
If you modify a JPEG and then Save As a JPEG, the quality will probably decrease. I tried it, but couldn’t see any difference. This is more of a problem with photographs. Screen resolutions differ, so this could also be a factor.
JPEG is a ‘lossy’ format. This means that when a JPEG is saved several times, information is lost and the quality decreases. PNG is a ‘lossless’ format which does not suffer from a drop in quality. Google PNG and JPEG to learn more about this subject.