The life cycle of StarsThe life cycle of Stars

Where do stars come Where do stars come fromfrom

Stars form in clouds of gas (a nebula)Stars form in clouds of gas (a nebula) These are called diffuse nebula or These are called diffuse nebula or

star forming nebula.star forming nebula. A single nebula can form hundreds or A single nebula can form hundreds or

even thousands of starseven thousands of stars Let’s see what they look like!!Let’s see what they look like!!

M8 – The Lagoon Nebula M16 – The Eagle Nebula

Star Forming RegionsStar Forming Regions

M17 and M20M17 and M20

What do new stars look What do new stars look likelike

New stars usually haveNew stars usually havePolar jets of gas and dust Polar jets of gas and dust A dark disk of material around its A dark disk of material around its

equatorequatorThey shine brightly in infrared but not They shine brightly in infrared but not

visible light because the cloud of gas visible light because the cloud of gas that the star forms from is blocking that the star forms from is blocking some lightsome light

Jets

What happens when What happens when stars start forming in stars start forming in nebulasnebulas Stars often form in groups called “clusters”Stars often form in groups called “clusters” There are two types of clustersThere are two types of clusters

1. 1. Open ClustersOpen Clusters usually have only a usually have only a few few hundred or a few thousand stars hundred or a few thousand stars

2. 2. Globular ClustersGlobular Clusters have hundreds of have hundreds of thousands of stars or even thousands of stars or even

millions of millions of stars stars

Open Cluster - M45Open Cluster - M45

The Pleiades – The Seven Sisters

Open Cluster – M67

Open ClustersOpen Clusters

Open clusters are still forming today Open clusters are still forming today from the larger gas cloudsfrom the larger gas clouds

Our Sun formed most likely was born Our Sun formed most likely was born in an open clusterin an open cluster

Open clusters are found inside our Open clusters are found inside our galaxygalaxy

The gravitational attraction between The gravitational attraction between the stars in an open cluster is not the stars in an open cluster is not strong enough to hold the cluster strong enough to hold the cluster together, so the stars go their together, so the stars go their separate ways and live individual separate ways and live individual liveslives

Globular clustersGlobular clustersM13 and M15M13 and M15

M5

M3

These globular clusters can These globular clusters can be very densely packedbe very densely packed

NGC 1850

Globular ClustersGlobular Clusters

Properties of Globular Clusters:Properties of Globular Clusters: They contain so many stars that gravity keeps the They contain so many stars that gravity keeps the

cluster intactcluster intact GC’s must have formed early in the universe when the GC’s must have formed early in the universe when the

clouds of gas were much larger and could produce clouds of gas were much larger and could produce more than a million stars at one timemore than a million stars at one time

No GC’s are forming today!No GC’s are forming today! GC’s contain many of the oldest stars in the universeGC’s contain many of the oldest stars in the universe GC’s are found in a halo surrounding the nucleus of GC’s are found in a halo surrounding the nucleus of

our galaxyour galaxy

OpenClusters

GlobularClusters

What happens at the end What happens at the end of the stars life?of the stars life?

Average stars produce planetary nebulaAverage stars produce planetary nebula When the core of the star starts a fusion reaction When the core of the star starts a fusion reaction

with the helium ash, the temperature increases with the helium ash, the temperature increases dramatically causing the outer layers to be puffed dramatically causing the outer layers to be puffed off.off.

Massive stars produce supernova explosionsMassive stars produce supernova explosions When larger stars start to produce iron at their When larger stars start to produce iron at their

core, it marks the beginning of the end. The core core, it marks the beginning of the end. The core collapses and then rebounds in a massive collapses and then rebounds in a massive explosion called a supernova!explosion called a supernova!

A glimpse at our A glimpse at our futurefuture

M57 – The ring Nebula

Ring Nebula from the Adler

M27 – The dumbell Nebula

NGC 7293 – The Helix Nebula

NGC 7293 – The Helix Nebula A close up view

M97 - The owl nebulaM97 - The owl nebula

NGC 2329 – The Eskimo Nebula

Supernovas

M1 – The Crab Nebula

M1 – The Crab Nebula

This star is in thelarge Magellanic

cloud and becamevisible to the naked

eye in 1987 but it actually exploded

about 180,000 years ago

M1 – The Crab Nebula

How do we know How do we know anything about stars?anything about stars?

From stellar spectrumFrom stellar spectrum We know the composition of the atmosphereWe know the composition of the atmosphere We know how fast the object is movingWe know how fast the object is moving We know how fast it is rotatingWe know how fast it is rotating We know the strength of its magnetic fieldWe know the strength of its magnetic field

How do we know the How do we know the temperaturetemperature

By looking at the colorBy looking at the color

RED = 3000 degreesRED = 3000 degreesYellow = 6000 degreesYellow = 6000 degreesBlue = up to 50,000 degreesBlue = up to 50,000 degrees

How did we figure the life How did we figure the life cycle of stars?cycle of stars?

We use an HR diagramWe use an HR diagram The HR diagram compares temperature The HR diagram compares temperature

to absolute brightnessto absolute brightness When we make this graph we find that When we make this graph we find that

the stars are only found in specific the stars are only found in specific locations.locations.