2. Not All Stars are the Same We will examine the following stages of life for stars: ▫ Birth ▫ Early life ▫ Major part of life ▫ Old age ▫ Death ▫ Remains The results of each stage will be different for each star depending on its mass

3. A Star is Born! A star is born from a cloud of dust and gas called a nebula Nebula means “mist” in Latin

4. Early Life A small star (like our Sun) will gradually turn into a hot, dense clump that begins to produce energy. This happens when parts of nebulae collapse in on themselves Gravity and mass will increase causing a tightly packed sphere of matter to form Eventually the pressure gets so high that nuclear fusion occurs

5. The Major Part of Life The star really turns “on” when nuclear fusion starts transforming Hydrogen into Helium This produces energy (light & heat) The Star stays in this state for most of its life The length of a star’s life depends on its mass and how quickly it uses up its Hydrogen For a star similar to our Sun, it will use nuclear fusion to produce energy for about 10 billion years

6. Old Age After a while, all of the hydrogen in the core of the star gets used up Helium is then used for nuclear fusion The core starts to collapse and the outer layers of the star expand

7. Red Giant As the outer layers expand, the star becomes a large, cool red giant Consider the size difference between the Sun and a Red Giant

8. Death Outer layers of the Red Giant drift away The core shrinks The star becomes a small, hot, dense white dwarf star Sirius (Dog Star) Sirius B – White Dwarf The white dwarf star will eventually cool off, and fade away Remains

9. Life of Bigger Stars For stars 10 times the size of the Sun: In a short time will become a hot dense clump, and use nuclear fusion to produce energy Uses nuclear fusion for a few million years They are 5000 times brighter than the Sun For stars 30 times the size of the Sun: In a very short time will become a hot dense clump, and use nuclear fusion to produce large amounts of energy Uses nuclear fusion for only about one million years They are extremely bright

10. Old Age Larger stars swell to become Red Supergiants Red Supergiant

11. Death of Bigger Stars Bigger stars have a more extravagant death Their cores collapse inwards, sending the outer layers exploding into a supernova

12. Remains of Bigger Stars Stars that are around 10 times the size of the Sun will turn into a neutron star after the supernova. Gases from a neutron star drift off as nebula and get recycled

13. Black Holes The largest of stars will end up as black holes http://hubblesite.org/explore_astronomy/black_holes/i ndex.html

15. Eagle Nebula

16. Heart Nebula