http://afrebel.scripts.mit.edu/www/theory
http://www.astro.yale.edu/larson/papers/SciAm04.pdf
https://www.nasa.gov/multimedia/imagegallery/image_feature_643.html
https://www.google.com.eg/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=rate+of+pulsar+star+shine
https://www.coursera.org/learn/evolvinguniverse/outline
http://www.history.com/shows/the-universe/videos/the-universe-life-and-death-of-a-star
refrences