- Medium-sized stars last for about ten billion years. Small stars may last for 200 billion years.
- Big stars have short, fierce lives of ten million years
- Stars that begin life in clouds of gas and dust are called nebulae.
- Inside nebulae, gravity creates dark clumps called EGGs (evaporating gaseous globules). Each clump contains the seeds of a family of stars.
- As gravity squeezes these globules, they shrink and from hot balls of gas and dust.
- Smaller clumps don’t get very hot, so they eventually fizzle out.
- If a larger clump reaches 10 millionÂ°C in its core, hydrogen atoms begin to join together in nuclear reaction and the baby star starts to glow.
- In a medium-sized star, such as the Sun, the heat of burning hydrogen pushes out as fiercely a gravity pulls inwards, and the star becomes stable (steady).
In the center of this massive galactic nebula is a cluster of young, bright stars.
Star are born and die all over the Universe, and by looking at stars in different stages pf their life, astronomers have learned about the stages of their existence.