star’s life cycle goal: create a diagram to help you understand this process do now: our sun is an...
TRANSCRIPT
Star’s Life Cycle
• Goal: Create a diagram to help you understand this process
• Do Now: Our Sun is an average size star –will it ever become a Black Hole? Why or why not?
Creating your diagram
• Sketch the basic design as we go and add information when we come to each stage
• You have a big sheet of paper so that you will have enough room to add information at each step
• Fold your paper in fourths to help with spacing• Use a pencil to sketch the circles, then add details
later – don’t worry about colors at this point.• Here’s a quick picture of what we will create
Summary of a Star’s “Life Cycle”
So, what is a star?
• A star is a really hot ball of gas, with hydrogen fusing into helium at its core. Stars spend the majority of their lives fusing hydrogen, and when the hydrogen fuel is gone, stars fuse helium into carbon.
• Throughout this whole process is that battle between gravity and gas pressure, known as equilibrium. It’s crucial to keep this battle in your mind when trying to understand how stars live and die.
• Let’s start the diagram!
Nebula
Nebula
• A cloud of gas and dust in space that comes together by gravity. Stars can form from the matter and energy in them.
• The nebula warms up, shrinks and becomes a proto-star (“pre” star)
Nebula Star
Main Sequence Star
• Nuclear reactions occur inside the star, light and heat is produced.
• Most of the stars life!!• It’s destiny depends on it’s
overall size.• Larger stars become
supergiants• Smaller stars become red
giants
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Let’s start with Smaller Stars
• Smaller stars last longer than the larger stars
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Vocab Review
• Red Giant – a large reddish star late in it’s life that converts helium into carbon or oxygen
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
Planetary Nebula
• A planetary nebula forms when a star can no longer support itself by fusion reactions in its center.
• The gravity causes it to collapse and heat up. • It lasts thousand years. • The core remnant is uncovered and heats the
now distant gases and causes them to glow.• Despite the name, it has nothing to do with
planets!
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf
Vocab Review
• White Dwarf – a small, dense star that remains after a red giant converts all of its helium into carbon or oxygen
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf Cools
Black Dwarf
Black Dwarf
• When a white dwarf cools to the point that it no longer emits significant heat or light.
• It takes tens to hundreds of billions of years for it to cool down entirely, and the Universe hasn't been around that long--the oldest stars are between 10 and 20 billion years old. Therefore there are no black dwarfs yet, but there will be in the future.
Now, Back to the Larger Stars…
• Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands times the solar luminosity.
• Because of their extreme masses they have short lifespans of only 10 to 50 million years and are only observed in young cosmic structures such as open clusters, the arms of spiral galaxies, and in irregular galaxies.
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf Cools
Black Dwarf
Vocab Review
• Red Supergiant - a large star late in its life cycle that converts its helium into iron
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf Cools
Black Dwarf
Super Nova
Vocab Review
• Supernova – a powerful explosion that occurs when a supergiant converts all of its helium into iron
• What causes a star to blow up?• Gravity gives the supernova its
energy. Once the core has gained so much mass that it cannot withstand its own weight, the core implodes
Supernova
• These have been observed!• Supernova explosions are relatively rare events in our
own galaxy, happening once a century or so on average.• In 1987, there was a supernova explosion in the Large
Magellanic Cloud, a companion galaxy to the Milky Way. Supernova 1987A,
which is shown below:
Two pathways
• There are two possible results of the supernovas:
• Neutron Star• or• Black hole
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf Cools
Black Dwarf
Super Nova
Neutron star
Black Hole
Vocab Review
• Neutron Star – a small, dense dead star that can remain after a supernova
Vocab Review
• Black Hole -• An extremely massive and dense object that
can remain after a supernova• These are so massive and dense that light
cannot escape its gravity
Finish your diagram
• Add the title, “Star’s Life Cycle”• Work with people at your table to make sure
you wrote down the important information.
Nebula Star
Super Giant
Red Giant
Large Stars
Small/Medium Stars
Planetary Nebula
WhiteDwarf Cools
Black Dwarf
Super Nova
Neutron star
Black Hole
Your Name
Star’s “Life Cycle”
Summary of a Star’s “Life Cycle”
Add 0n Vocabulary
Fusion • This is the process where smaller atoms are
combined to form larger atoms. On the sun, hydrogen atoms are fused or joined into a helium atoms. The by-product of this process is heat and light.
Vocabulary from your book
• In your own words, define the vocab (Geo Words) and add it to your glossary from p.729-733 + nebula:
• *luminosity • *molecular cloud • *supernova • *neutron star • *stellar black hole • *nebula