Universe Characteristics of Stars Elements

							Characteristics of Stars
        Elements in Stars
   99% Hydrogen (H) and Helium (He)

   1-2% Oxygen, Carbon, Nitrogen, Calcium

   Sun is 70% Hydrogen and 28% Helium

   Produce energy (heat and light) by fusing hydrogen
    atoms to make helium
      Physical Properties of Stars
Star Color is dependant on surface temperature.
 Hot stars = Blue or White, ~30,000 K

 Cool stars = Red or Orange, ~3,000 K

 The Sun = Orange or Yellow, ~5,500 K
         Absolute Magnitude
   Stars actual brightness  distance of 32.6 light
    years from the sun

   Depends on size and temperature of the star.

What would the brightest star look like?
At this size, a
dwarf star is too
small to see
1. Each letter represents a star, what type is each and what
color is each?
2. What 2 things does this diagram tell you about stars?

                                          D
      C

                                                     E
                          B


            A

   High Temp                             Low Temp
Answers…
   A – White Dwarf, White
   B – Main Sequence, Yellow
   C – Main Sequence, Blue
   D – Super Giant, Red
   E – Giant, Red

   Surface Temperature & Absolute
    Magnitude (Brightness)
         Origin of Stars
    Nebulae (huge clouds of hydrogen gas and dust)
1.    Diffuse Nebula: visible due to the light provided
      by close stars
2.    Dark Nebula: blocking other stars
          Formation of Protostars
   Something outside the nebula triggers the
    gravity between gasses and dust
       A supernova shockwave
   Nebula contract
   As the nebula contracts, spots in it start to glow
    with heat  protostar
        Formation of Main Sequence
        Stars
   Protostar continues to contract  Fusion begins

 IMPORTANT: STARS ARE ALWAYS TRYING TO
      COLLAPSE DUE TO THEIR OWN GRAVITY
 It keeps collapsing until the star’s released energy

  equals the force of gravity
 It is now a Main Sequence Star
        Formation of Giants/Supergiants
   Hydrogen decreases  energy of fusion no longer
    balances the force of gravity

   Core of the star contracts and get hotter

   Increases the rate of fusion for the remaining
    Hydrogen

   The increased energy causes the outer layers to
    expand  Giant/Supergiant
        Formation of Dwarfs
   No fuel  Star collapses due to gravity

   Squeezes the nuclei together very tightly dwarf

   The can glow for billions of years as they cool
    Non Massive Star Life Cycle
Nebula
        Massive Star Life Cycle:
        Supernova
   Fusion stops in massive stars  forms super
    dense core with extremely strong gravity
   The gravity causes the star to collapse past the
    dwarf stage
   Collapse puts intense pressure on the core
   Star explodes violently and half its mass is
    blown away  supernova
Supernova Before and After
        Neutron stars
   Leftover half of supernova that doesn’t blow up
   Its gravity is so strong that all of the atoms
    particles (p+, n, e-) are crushed together,
    leaving only neutrons
   Neutron stars may be 10km wide, are a trillion
    times as dense as the sun.
        Black Holes
   If the star is massive enough, its gravity causes
    it to collapse past the neutron phase into a tiny
    volume, but humongous density/gravity 
    Black Hole

   The gravity is so great that not even light can
    escape
        How do we know they exist?
   Strong X-Ray emissions from the Cygnus
    constellation

   When something gets sucked into a black hole,
    its atoms get ripped apart and it emits x-rays
Galaxies and Universe
   Solar system - the sun, orbiting planets,
    asteroids, meteors, and comets

   The sun is 1 star in a galaxy, which is a group of
    millions or billions of stars held together by
    gravity

   Our galaxy is in the universe, which contains all
    the planets, stars, solar systems, and galaxies
        The Milky Way
   100 billion stars
   Every visible star
   It is 1 of 17 nearby
    galaxies that make up
    the Local Group
        Milky Way Facts
   Diameter: 140,000 light
    years
   Width: 20,000 light       That’s Us!
    years
   Sun 23,000 light years
    from the center
        Sprial Galaxies
   Spiral Galaxies central nucleus, arms coming
    off the nucleus.
Barred Spiral Galaxies
       Elliptical Galaxies
   Range from spherical to lens shaped most
    common
        Irregular Galaxies
   Smaller, fainter, and less common, no pattern
       Big Bang Theory
    Universe began as a dense sphere of
     hydrogen.
    13.7 billion years ago it exploded, forming a
     gigantic, expanding cloud of gas and dust

    Evidence
1.    Red Shift
2.    Microwave Radiation