The life cycle of Stars

Where do stars form  Stars form in clouds of gas (a nebula)  These are called diffuse nebula or star forming nebula.  A single nebula can form hundreds or even thousands of stars  Let’s see what they look like!!

M8 – The Lagoon NebulaM16 – The Eagle Nebula Star Forming Regions

M17 and M20 M17 and M20

What happens when stars start forming in nebulas  Stars often form in groups called “clusters”  There are two types of clusters 1. open clusters usually have only a few hundred stars and are found inside galaxies 2. globular clusters have hundreds of thousands of stars

Open cluster - M45 The Pleiades – The Seven Sisters

Globular clusters M13 and M15

These globular clusters can be very densely packed

What happens at the end of the stars life?  Average stars produce planetary nebula  When the core of the star starts a fusion reaction with the helium ash, the temperature increases dramatically causing the outer layers to be puffed off.  Big stars produce supernova explosions  When larger stars start to produce iron at their core, it marks the beginning of the end. The core collapses and then rebounds in a massive explosion called a supernova!

A glimpse at our future M27 – The dumbell Nebula M57 – The ring Nebula

More Planetaries M97 - The owl nebula NGC 7293 – The Helix Nebula

What about supernovas This star is in the large Magellanic cloud and became visible to the naked eye in 1987 but it actually exploded about 180,000 years ago

How do we anything about stars?  From their spectrum  We know the composition of the atmosphere  We know how fast the object is moving  We know the strength of its magnetic field

How do we know the temperature  By looking at the color  RED = 2000 degrees  Yellow = 6000 degrees  Blue = up to 100,000 degrees

How did we figure the life cycle of stars?  We use an HR diagram  The HR diagram compares temperature to brightness