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ASTRONOMY

ASTRONOMY. Chapter 22 Our Star, the Sun. Structure. Structure. The photosphere, chromosphere, and corona make up the atmosphere of the sun. These layers do not contribute much to the total mass of the sun. The Photosphere. The photosphere is the part of the sun you can see.

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ASTRONOMY

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  1. ASTRONOMY Chapter 22 Our Star, the Sun

  2. Structure

  3. Structure • The photosphere, chromosphere, and corona make up the atmosphere of the sun. • These layers do not contribute much to the total mass of the sun.

  4. The Photosphere • The photosphere is the part of the sun you can see. • It is NOT a surface – the sun is made of gas. • The Diameter of the Sun is usually the diameter of the photosphere. • The photosphere is about 1.4 million km across.

  5. Definition • As we look down into the atmosphere at the surface of the Sun the view becomes more and more opaque. The point where it appears to become completely opaque is called the photosphere. Thus, the photosphere may be thought of as the imaginary surface from which the solar light that we see appears to be emitted. http://csep10.phys.utk.edu/astr162/lect/sun/photosphere.html

  6. The Photospheric Spectrum • The solar spectrum is (nearly) continuous. • It shows many Fraunhofer (absorption) lines. • Caused by elements in the gas above it.

  7. Granulation • The photosphere exhibits granulation. • Caused by convection. • Each is about 1000 km across.

  8. The Chromosphere • The chromosphere is an irregular layer above the photosphere where the temperature rises from 6000°C to about 20,000°C. At these higher temperatures hydrogen emits light that gives off a reddish color (H-alpha emission). This colorful emission can be seen in prominences that project above the limb of the sun during total solar eclipses. This is what gives the chromosphere its name (color-sphere). http://solarscience.msfc.nasa.gov/chromos.shtml

  9. The Chromosphere • The chromosphere is about 2000 km deep. • The Temperature generally increases with distance from the photosphere. • It is less dense than the photosphere and more dense than the corona. • Appears reddish in color from the red hydrogen emission line.

  10. Chromosphere • Spicules • 700 km across by 7000 km tall. • 5-15 min lifetime. • About 500,000 on sun at any time. http://sohowww.nascom.nasa.gov/pickoftheweek/old/09aug2007/304spicules.jpg

  11. Corona • The corona is the outer-most part of the solar atmosphere. • Only visible during a total eclipse. • Extremely low density • Less than one-billionth the density of the Earth’s atmosphere at the surface. • Very hot • Very few particles are moving at very high speeds.

  12. Prominences • Prominences are dense clouds of material suspended above the surface of the Sun by loops of magnetic field. Prominences and filaments are actually the same things except that prominences are seen projecting out above the limb, or edge, of the Sun.

  13. Prominences http://apod.nasa.gov/apod/image/9909/equinoxprom_eit.jpg

  14. Prominences http://www.csmonitor.com/var/ezflow_site/storage/images/media/images/2010/0512/0512-solar-prominence/7883793-1-eng-US/0512-solar-prominence_full_600.jpg

  15. Prominences

  16. Coronal Mass Ejections • Sometimes, prominences will eject matter into space. • This blob of high-energy particles can kill astronauts or produce incredible aurorae. • CMEs happen from once to several times per day.

  17. Coronal Mass Ejections http://www.nustar.caltech.edu/uploads/images/site/coronal_mass_ejection.jpg

  18. Coronal Mass Ejection The photo shows the effects of a coronal mass ejection — large clouds of plasma and magnetic field that erupt from the sun – striking Earth’s magnetic field. http://blog.chron.com/sciguy/2012/10/the-most-awesomest-picture-youll-see-today/?fb_action_ids=10151186581359764&fb_action_types=og.recommends&fb_source=timeline_og&action_object_map=%7B%2210151186581359764%22%3A114966428660942%7D&action_type_map=%7B%2210151186581359764%22%3A%22og.recommends%22%7D&action_ref_map=%5B%5D&replytocom=158296

  19. Studying the Sun • The corona can be study with a coronagraph. • It is best studied with coronagraphs and total solar eclipses. • The next solar eclipse will happen on November 13, 2012 across Australia and the South Pacific.

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