Good Afternoon!

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Good Afternoon!

• Please get your eInstruction remote and notebook.

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• The sun is a medium sized star. The sun is about
  75 Hydrogen and 25 Helium. Where is the sun
  located on the H-R Diagram?
• White Dwarfs
• Main Sequence
• Supergiants
• Red Giants

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Lives of Stars

• 8th Grade Science
• http//hubblesite.org/gallery/tours/

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Left Column Questions

1. How do scientists classify stars?
2. What determines a stars lifetime?
3. List the phases of the life cycle of a Sun-like
   star.
4. List the phases of the life cycle of a Supergiant
   star.

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How do scientists classify stars?

• Size and mass
• neutron stars, dwarfs, main sequence, red
  giants, supergiants
• Temperature and color
• star color is related to its surface temperature
• Brightness and luminosity
• star luminosity depends on brightness and
  distance from Earth

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Lifetimes of Stars

• A stars life depends on its mass
• Stars smaller than the sun live up to 200 billion
  years.
• Medium sized stars like the sun live around 10
  billion years.
• Stars 15 times more massive
• than the sun live about 10 million years.

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Life cycle of a Sun-like star

• nebula
• protostar
• main sequence
• red giant
• planetary nebula
• white dwarf

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Lives of Stars

• Stars begin as gas and dust called a nebula.
• Helix Nebula Crab Nebula
• http//hubblesite.org/gallery/tours/tour-helix/
• http//hubblesite.org/gallery/tours/tour-carina/

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Protostar

• Gravity pulls the gas and dust in and nuclear
  fusion begins. This forms a Protostar or new
  star.

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Main Sequence Star

• Once nuclear fusion begins, a star is in the main
  sequence stage of its life cycle.
• This is the longest and most stable part of a
  stars life.

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Red Giant

• The star begins to cool and the outer layers
  expand.

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Small and Medium Stars

• These become giants and then
• Planetary Nebula a shell of gas is ejected from
  the core of the star.
• White Dwarfs blue-white core of a star that is
  left behind.
• These have no fuel, but glow faintly from left
  over energy.
• When a white dwarf burns out, it is dead. Then
  it is a Black Dwarf.

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Planetary Nebula
http//www.nasa.gov/mission_pages/hubble/science/n
gc5189.html
Planetary nebulae represent the final brief stage
in the life of a medium-sized star like our sun.
While consuming the last of the fuel in its core,
the dying star expels a large portion of its
outer envelope. This material then becomes heated
by the radiation from the stellar remnant and
radiates, producing glowing clouds of gas that
can show complex structures, as the ejection of
mass from the star is uneven in both time and
direction.
Explore a planetary nebula http//hubblesite.org/
gallery/tours/tour-catseye/
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WHITE DWARF The White Dwarfs are circled in the
Hubble Space Telescope image below.
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Star Life Cycle

• http//science.nasa.gov/astrophysics/focus-areas/h
  ow-do-stars-form-and-evolve/
• A star can take 2 paths, depending on its size
  or mass.

Main Sequence
Small/Medium Size Star
Giant and Supergiant Stars
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The life of Large Stars

• Nebula
• Protostar
• Main Sequence
• Super Giant The star begins to run out of fuel.
  The star cools and expands.
• Supernova Massive stars can blow up to an
  enormous size.
• Neutron Star/Pulsar or Black Hole

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Super Nova The explosion of a dying giant or
supergiant star Keplers Supernova Remnant
http//hubblesite.org/gallery/album/query/supernov
a/
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Super Giants

• When a Super Giant explodes into a supernova, it
  can become 2 things
• 1. Neutron Star Smaller and more dense than a
  white dwarf. They have 3 times as much mass as
  the sun, but are about the size of Houston!
• 2. Black Hole This object is so dense, not even
  light can escape the gravity field.
  http//imagine.gsfc.nasa.gov/docs/science/know_l2/
  black_holes.html

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Pulsar

• A neutron star that produces radio waves.
• Pulsars appear to pulse because they rotate!

http//imagine.gsfc.nasa.gov/docs/science/know_l2/
pulsars.html
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Small/Medium Size Stars
Giant and Supergiant Stars
Can blow up into Supernovas.
Become red giants and then a planetary nebula.
The remains of a supernova become a neutron star
or a black hole.
When a white dwarf runs out of energy, it turns
into a black dwarf.
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The life cycle of a low mass star (left oval) and
a high mass star (right oval).
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Binary Star Systems

• A star system with two stars.
• Stars that revolve around each other.
• Sometimes this causes stars to appear as if they
• are blinking

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Lets Review!

• 1. All stars begin as gas and dust and is called
  a
• a. Protostar
• b. Nebula
• c. White dwarf
• d. Supernova

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• 2. Most stars are in this stage
• a. Protostar
• b. White Dwarf
• c. Main Sequence
• d. Neutron Star

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• 3. The life of a star depends on its
• a. Color
• b. Place in the universe
• c. Mass
• d. Temperature

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• 4. If the star is super massive, it will live
  longer.
• a. True
• b. False

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• 5. Low mass stars will become black holes
• a. True
• b. False

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• 6. An object so dense, not even light can escape.
• a. Supernova
• b. Main Sequence
• c. Black Hole
• d. Nebula

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• 7. A new star where fusion begins.
• a. Protostar
• b. Neutron Star
• c. Main Sequence
• d. Black Hole

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• 8. The most common chemical element in a star is
• A. Helium
• B. Hydrogen
• C. Carbon
• D. Sodium

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• 9. The sun formed out of a
• A. Pulsar
• B. Supergiant star
• C. White Dwarf
• D. Nebula

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10. Compared to Rigel, Alpha Centauri B is

1. Cooler and brighter
2. Cooler and dimmer
3. Hotter and brighter
4. Hotter and dimmer