1 / 12

ASTRONOMY

ASTRONOMY. Chapter 27 The Birth, Youth, and Middle Age of Stars. Formation of Stars. Stellar evolution Born from a cloud of gas and dust A region becomes more dense Random density fluctuation Shock wave from a supernova Gravity attracts more gas and dust

paytah
Download Presentation

ASTRONOMY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. ASTRONOMY Chapter 27 The Birth, Youth, and Middle Age of Stars

  2. Formation of Stars • Stellar evolution • Born from a cloud of gas and dust • A region becomes more dense • Random density fluctuation • Shock wave from a supernova • Gravity attracts more gas and dust • Energy from the contraction heats the gas • This protostar gives off electromagnetic radiation.

  3. Evolutionary Track • The life history of a star can be plotted on the H-R diagram. • Each point on the graph represents a particular moment in the star’s life.

  4. High Mass vs. Low Mass • High mass protostars will contract more quickly than lower mass protostars • What takes a 1 solar mass protostar 50 million years will only take a 10 solar mass protostar about 200,000 years.

  5. The Nuclear Furnace • As a star collapses, the gravitational potential energy of the gas particles is converted to heat. • The center of the star heats up and the pressure builds until conditions are right for nuclear fusion.

  6. Atoms • Atoms are made of protons, neutrons, and electrons. • Protons and neutrons are in the nucleus and electrons are located in the electron cloud. • The nucleus is about 1/10,000th the diameter of the atom. • Most of an atom is empty space. • When an atom gains or losses electrons, it is called an ion.

  7. Plasma • In a star, the hydrogen atoms lose their electrons and form plasma, the 4th state of matter. • This is why matter from a star is so dense. • In the center of a star, the hydrogen nuclei – protons – are very close together and moving very fast.

  8. Nuclear Fusion

  9. Nuclear Fusion • In the core of a star (generally): • Four hydrogen nuclei combine to make a helium nucleus. • A little mass is “lost”. • The “lost” mass is converted to energy according to the equation E=mc2. • A small amount of mass gives a huge amount of energy.

  10. Nuclear Fusion • The exact nuclear reaction is believed to depend on the core temperature of the star: • At 15 million K the proton-proton star chain dominates. (p 512) • Above 15 million K the carbon-nitrogen-oxygen cycle dominates. (p 513) • Above 108 K the triple alpha process occurs. (p 514)

  11. Nuclear Fusion • Once nuclear fusion starts, the outward thermal pressure will balance the inward force of gravity. • The star reaches hydrostatic equilibriumand settles into its place on the main sequence. • The star is now in the prime of its life.

  12. The End

More Related