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Stars and Galaxies

Stars and Galaxies. The Big-Bang Theory. States that the universe began to expand with an explosion of concentrated matter and energy and has been expanding ever since. Locating Stars.

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Stars and Galaxies

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  1. Stars and Galaxies

  2. The Big-Bang Theory • States that the universe began to expand with an explosion of concentrated matter and energy and has been expanding ever since.

  3. Locating Stars • Doppler Effect- apparent change in the wavelengths of light that occurs when an object is moving toward of away • Red shift- objects moving away • Blue shift- objets moving toward

  4. Distance to the Stars • Parallax is the apparent shift in the position of an object when viewed from two different positions. Fig 2-26. • Light Year is the distance light travels in one year. 300,000 km/s or 9.5 trillion kilometers in one year.

  5. Stars • Constellations are groups of stars that are named after animals, characters in mythology, or familiar objects.

  6. Magnitude • Absolute magnitude of a star is the measure of the amount of light it actually gives off. • Apparent magnitude of a star is the measure of the amount of light received on Earth.

  7. Star Temperature • The color of a star gives an indication of the temperature of a star.

  8. The Sun • 99% of all matter in the solar system • a yellow main sequence star

  9. Sun’s Atmosphere • Photosphere: 6000oC, light is given off here • Chromosphere: above the photosphere • Corona: extends out into space 2,000,000oC

  10. Sun’s Surface • Convection Zone • Radiation Zone • Core

  11. Sun’s Surface Features • Sunspots: areas that appear darker, cooler than surrounding areas. • Prominences and Flares: gases near sunspots brighten suddenly, shooting gas outward at high speeds, high energy particles form the sun are caught by the Earth’s magnetic field and disrupt communications, cause Aurora Borealis.

  12. A Star’s Birth • Stars are born in a nebula • nebula a large cloud of dust and gas in space • As this cloud of dust and gas develops a core and gravity it collapses inward and starts a nuclear reaction (fusion) • most star systems are binary, they have two stars

  13. Star Facts • Most star systems are binary. • The main sequence is the general evolution of stars. (H-R Diagram Fig. 2-25) • Stars produce energy by fusion.

  14. Star Evolution • Nebula: large cloud of dust and gas, the birth place of stars. • Main Sequence shows the evolution of a star • Giants, as stars burn out the get larger. • White Dwarf: hot dense core left after fuel is burned out.

  15. The Evolution of Super Giants • Ten times more massive than our sun • Violent collapses • Explosion is called a Supernova. • Neutron Star: the dense core left from a supernova. • Neutron Stars continue to collapse which can result in a black hole.

  16. Galaxies • Galaxies are large groups of stars. • Elliptical galaxies form a three-dimensional ellipse. • Spiral galaxies have a central mass with spiral arms. • Irregular Galaxies have no defined shape. • Our Galaxy is a spiral galaxy called the Milky Way.

  17. ELLIPTICAL GALAXY

  18. IRREGULAR GALAXY

  19. The Universe • The Universe is the inclusion of all the galaxies. • The Universe is believed to be expanding. • This belief is based on Doppler Shift observations.

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