Vicki Murillo Amherst Education Center Earth Science March 2010

 After this lesson, you will be able to:  List the sequence of stages in the evolution of both low mass and high mass stars  Describe how the gas composition of a star changes as it evolves  Track the position of a star on a H-R diagram as it evolves

Eagle NebulaOrion Nebula Image credit:

 Nebula: a large cloud of gas and dust where stars form  A nebula contracts due to the force of gravity exerted by the particles of gas and dust.  As the particles condense and move closer together, temperature increases.  Fusion begins at 10 million degrees K (~ 18 million °F).  Energy radiates into space.

 Four hydrogen (H) nuclei combine to create one helium (He) nucleus, releasing huge amounts of energy Image credit:

 The life cycle of a star depends on its mass.  Low mass stars spend much more time in the main sequence stage and eventually end up as white dwarfs.  High mass stars evolve more quickly and violently. They end up as neutron stars or black holes.

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Image credits: Main sequence star (Proxima Centauri) White Dwarf (Sirius B) Increasing time Nebula (Eskimo) Red Giant (Arcturus)

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Image credits: Supergiant (Betelgeuse) Main sequence star (Regulus compared to Sun) Supernova (M1) Neutron Star Black Hole (NGC 1097) Nebula (Cone)

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 Supernova: the explosion of the outer portion of a supergiant.  Neutron star: a supernova becomes a neutron star if its mass is between 1.4 and 3 times that of the Sun. Neutron stars are so dense that a teaspoonful would weigh more than 600 million tons in Earth’s gravity.  Black hole: If a supernova’s core is more than 3 times the Sun’s mass, it becomes a black hole. Its gravity is so strong that nothing can escape from it, not even light.

 As supernovas explode, they release clouds of gas and dust. This material is recycled and is used to form new stars.  Crab Nebula:  A supernova remnant  Observers in China and Japan recorded the supernova nearly 1,000 years ago, in Image credit:

 Are you able to:  List the sequence of stages in the evolution of both low mass and high mass stars?  Describe how the gas composition of a star changes as it evolves?  Track the position of a star on a H-R diagram as it evolves? Let’s give it a try!

Image credits: Main sequence star (Proxima Centauri) White Dwarf (Sirius B) Increasing time Nebula (Eskimo) Red Giant (Arcturus)

Image credits: Supergiant (Betelgeuse) Main sequence star (Regulus compared to Sun) Supernova (M1) Neutron Star Black Hole (NGC 1097) Nebula (Cone)

Image credits: What will happen to these percentages in the future? Why?

Image credit: Which stars are the youngest? Oldest? Which started as high mass stars? Where is our Sun and what will happen to it?