NASA's Chandra X-ray Observatory is a space telescope specially designed to detect the X-rays that are normally absorbed by Earth's atmosphere. Because Chandra orbits above it, up to an altitude of 139,000 km (86,500 mi), it can detect these X-ray emissions that come from very hot regions of the Universe. Exploded stars, galaxy clusters, matter around black holes. Things that are invisible to the naked eye but show up in X-ray.
Now check out this really neat, interactive guide to stellar evolution from the Chandra X-ray Observatory. Through this interactive guide you can see examples of stars at various evolutionary stages, and what Chandra has learned about them.
Find the guide by going to the Chandra X-ray Observatory Website, clicking the image above, or copy this link (http://chandra.si.edu/resources/flash/stellar_evolution.html) into your browser.
Chandra also has a Facebook page