Lives of Stars

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Lives of Stars

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

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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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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 Star

• Crab Nebula
• Gas pillars in the Eagle Nebula

• Stars form in a cloud of gas and dust called a
  nebula.
• http//hubblesite.org/gallery/tours/tour-carina/

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Protostar

• Gravity causes the densest parts to collapse
  forming a protostar or new star. Nuclear fusion
  begins.
• The red stars in the picture are protostars

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Main Sequence

• Stars spend most of their lives on the main
  sequence.
• A star becomes a main sequence star as soon as it
  begins to fuse hydrogen into helium.
• http//science.nasa.gov/astrophysics/focus-areas/h
  ow-do-stars-form-and-evolve/

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Red Giant

• When a stars hydrogen supply is nearly gone, the
  star moves off the main sequence.
• Thermal energy in the stars center causes the
  outer layers to expand and cool.

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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

• White Dwarfs blue-white core of a star that is
  left behind.
• These have no fuel, but glow faintly from left
  over energy.
• The White Dwarfs are circled in the Hubble Space
  Telescope image below.

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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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Super Nova The explosion of a dying giant or
supergiant star
http//hubblesite.org/gallery/album/query/supernov
a/
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End of a Super Giant

• 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/science/objects/black
  _holes1.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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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