Download Life and Death of a Star

Life and Death of a Star
Sources of Energy
• A Star has Two Sources of Energy
• Source 1: Fusion
– The Conversion of Light Elements into
Heavier Ones
• Source 2: Gravity
– The attraction of each atom in the star to
every other atom
Sources of Energy
• Fusion
–The joining of Hydrogen Nuclei to
make Helium
–Can also join Helium Nuclei to make
Beryllium
–Attempts to Blow the Star apart
–Happens only at the very Core of the
Star
Sources of Energy
• Gravity
–Draws all the matter of the Star
inward
–Is the weakest of all the fundamental
forces
–Grows in strength as the amount of
matter increases or the size of the star
shrinks
Life of a Star
• Main Phases of a Star’s Birth
– Formation of Cloud
• Gathering of Innerstellar Dust
• Innerstellar means the stuff between Stars
– Cloud to Protostar
• Formation of the Seed that will become a
Star
– Protostar to Star
• Heating up to full fledged Star
Life of a Star
• Stellar Cloud
– Begins at a cool temperature of 10-30K
– Planet Earth is Typically around 300K
– Cloud begins to shrink and glow
Life of a Star
• Protostar
– The Stellar Cloud collapses so much that
the internal temperature and pressure
rise dramatically
– The Core begins to push back against
Gravity and the Protostar is formed
– The core is NOT yet hot enough for
Fusion
– However the seed of a new star is planted
Life of a Star
• Star
– When the Internal Temperature reaches
10 million K, it is hot enough for Fusion
to start
– The Hydrogen burning star is born and
maintains a balance between gravity and
pressure
– This balance is known as gravitational
equilibrium
– This is now a main sequence star
Mass of a Star
• Every Star in the Universe is compared
to our Sun when we talk about mass
• Our Sun is designated as having 1 Solar
Mass
• Thus a Star with 4 Solar Masses is 4
times bigger than our Sun
• Every Star has a specific Mass when it
is born that will determine the Star’s
eventual fate
Mass of a Star
• Birth Weights - there are 3 possible
birth weights for a Star
– Low Mass Star: 0.5 - 2 Solar Masses
– Intermediate Mass: 2 - 8 Solar Masses
– High Mass Star: 8 Solar Masses or Bigger
• The Fate of Each individual Star
depends almost entirely on its Birth
Mass
Size and Fate
• Bigger Stars form faster and burn
hotter and brighter, but die Faster and
more spectacularly
• Smaller Stars take longer form, burn
cooler, but live much longer and have
Simple Deaths
• Big Stars may only live for hundreds of
Million of years
• Small Stars may live for Billions
Astronomy Assessment
• In class essay that will take place
during your lab day
• Minimum of 3 paragraphs: Intro, Body
and Conclusion
• Minimum of 1 hand written page or
300 words
• May bring in any notes to use during
the essay writing
Essay Prompts
• Compare and Contrast the Life of a Star to
the Life of a Human. Mention the Growth,
Stages of Development, Life Expectancy,
and Death of Each.
• Compare and Contrast the Formation, Life,
Destruction and Recycling of Veterans
Stadium to a Solar System
• Compare and Contrast the Big Bang to a
Bag of Microwavable Popcorn. Relate the
Formation, Expansion, Life Time, Collapse
and Destruction of Each.