What does the word “Evolution” mean? Bellwork 11/18: What does the word “Evolution” mean?

Today: Bellwork Warm up & quick notes Stellar Evolution Simulation Discuss Stellar Remnants Finish “Sisters of the Sun”?

Discuss with your table partner: Based on your reading from the book, match each phase of a human life cycle with each phase of a star’s life cycle. Human Life Cycle Stages Stellar Life Cycle Stages Gamete Fetus Childhood-Young Adult Hood Middle Age Old Age-Death Red Giant/Supergiant Fusion Ignition/Main-sequence Nebula Stellar Remnant Protostar

Stellar evolution Changes in a star’s properties over its “life” Stars exist because of gravity Two opposing forces in a star are Gravity – contracts Thermal nuclear energy – expands

Stages (5 Total) Nebula Birth In dark, cool, interstellar clouds Gravity contracts the cloud Temperature rises Radiates long-wavelength (red) light

Stages 2. Protostar Gravitational contraction of gaseous cloud continues Hydrogen nuclei fuse Become helium nuclei Process is called hydrogen burning Energy is released Outward pressure increases

3. Main-sequence stage When outward pressure is balanced by gravity pulling inward Hydrogen continues to fuse into Helium 90% of a star's life is in the main-sequence There are lots of types of Main-sequence stars. Why? What determines where they fall on the H-R Diagram?

4. Red giant stage Hydrogen burning migrates outward Star's outer envelope expands Surface cools & becomes red Core is collapsing as helium is converted to carbon Eventually all nuclear fuel is used Gravity squeezes the star Unbalanced forces

5. Burnout or Death OPTIONS: White Dwarf Planetary Nebula Supernova Black Hole Neutron star What determines which of these outcomes will occur? Let’s take a look…

Stellar Evolution Simulation You will begin as 1 of 4 main-sequence type stars You will travel through stations, recording your star’s evolution You will be collecting information on intermediate and ending phases

The Basics: Choose a “star” out the beaker. Determine which type of star you are based on the data given & your HR Diagram Follow the directions at each table. Make sure to collect information at each station Record your evolutionary pathways on the class data table, please.

You can start out as 1 of 4 stars: Brown Dwarf Red Dwarf Average/Solar-type Blue Supergiant

Stellar Remnants

White Dwarf Small (some no larger than Earth) Dense Can be more massive than the Sun Spoonful weighs several tons Atoms take up less space Electrons displaced inwards

Neutron Star Forms from a more massive star Remnant of a supernova Star has more gravity Squeezes itself smaller Remnant of a supernova Gravitational force collapses atoms Electrons combine with protons to produce neutrons VERY Small size

Neutron Star Pea size sample Weighs 100 million tons

Black Hole More dense than a neutron star Intense surface gravity lets no light escape As matter is pulled into it Becomes very hot Emits x-rays Likely candidate is Cygnus X-1, a strong x-ray source