There is a special fascination for Origin Stories that extends beyond comic books to almost all aspects of human activity. From the special episode of Friends were we learn how all the characters ended up sharing the same apartment to my daughters insistence on being told her the tale of her birth again and again, we all want to know how things began. Astronomy is no different. There are many stories to tell of the heavens - exploding supernova, colliding asteroids, cosmic rays crashing through the atmosphere. Stories of beginnings however seem to hold a special interest.
Astronomers think they understand how stars are born.
Every so often a chunk of a giant interstellar cloud of gas and dust falls victim to its own gravity. Matter rains down on the cloudlet's center and slowly a proto-stellar core is assembled from the infalling gas. As more matter rains down on the newly formed core, the pressure and temperature at its center increase until nuclear reactions begin. Once the nuclear flame is lit the lights go on in earnest and a new star is born. Energy generated by the nuclear engine at the young star's core give it support against its own ever-increasing gravity.