The life cycle of Stars

Where do stars come from  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 do new stars look like  New stars usually have  Polar jets of gas and dust  A dark disk of material around its equator  They shine brightly in infrared but not visible light because the cloud of gas that the star forms from is blocking some light

Jets

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 or a few thousand stars 2. Globular Clusters have hundreds of thousands of stars or even millions of stars

Open Cluster - M45 The Pleiades – The Seven Sisters

Open Cluster – M67

Open Clusters  Open clusters are still forming today from the larger gas clouds  Our Sun formed most likely was born in an open cluster  Open clusters are found inside our galaxy  The gravitational attraction between the stars in an open cluster is not strong enough to hold the cluster together, so the stars go their separate ways and live individual lives

Globular clusters M13 and M15

M5 M3

These globular clusters can be very densely packed

NGC 1850

Globular Clusters  Properties of Globular Clusters:  They contain so many stars that gravity keeps the cluster intact  GC’s must have formed early in the universe when the clouds of gas were much larger and could produce more than a million stars at one time  No GC’s are forming today!  GC’s contain many of the oldest stars in the universe  GC’s are found in a halo surrounding the nucleus of our galaxy

Open Clusters Globular Clusters

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.  Massive 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 M57 – The ring Nebula

Ring Nebula from the Adler

M27 – The dumbell Nebula

NGC 7293 – The Helix Nebula

A close up view

M97 - The owl nebula

NGC 2329 – The Eskimo Nebula

Supernovas

M1 – The Crab Nebula

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

M1 – The Crab Nebula

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

How do we know the temperature  By looking at the color  RED = 3000 degrees  Yellow = 6000 degrees  Blue = up to 50,000 degrees

How did we figure the life cycle of stars?  We use an HR diagram  The HR diagram compares temperature to absolute brightness  When we make this graph we find that the stars are only found in specific locations.