1 core maxing out when playing the Star Wars Blu Rays is normal behavior unfortunately. 20th Century Fox has done something with their DRM that causes CPU usage on one core to max out with a lot of their recent BluRay releases, including the Star Wars saga. Be thankful you are getting proper playback at least, when the discs first launched, they would get picture corruption when played on most BluRay playback software.
Edit: 90 degress is too hot for a load temp on the CPU, even in a laptop, you may want to blow any dust out of your laptop's air intakes. Opening up the computer and blowing the dust off the fans would also help your temps. Make sure that your laptop can breathe, and that its air intakes aren't blocked. If that doesn't lower your temps, it could be a CPU fan issue.