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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.